FDA Wellness and Software Claims: Intended Use Across Channels

Executive Summary

Within a 23-day window in January 2026, the U.S. Food and Drug Administration (FDA) Center for Devices and Radiological Health (CDRH) issued two superseding final guidance documents that updated the agency's non-binding interpretation of statutory software exclusions and enforcement-discretion policy for digital health products: General Wellness: Policy for Low Risk Devices (Document Number 1300013, issued January 6, 2026, superseding the September 27, 2019 edition) [1] and Clinical Decision Support Software (Document Number GUI01400062, issued January 29, 2026, superseding the January 6, 2026 edition) [2]. Together with FDA's Policy for Device Software Functions and Mobile Medical Applications (Document Number 1741, issued September 28, 2022, updated with a February 2, 2024 Quality Management System Regulation cover note) [3], the statutory exclusions in Section 520(o) of the Federal Food, Drug, and Cosmetic Act (21 U.S.C. § 360j(o)), and the codified intended-use regulation at 21 CFR § 801.4 (86 FR 41383) [8] [9], these documents define how FDA evaluates whether physiological sensor outputs, mobile application interfaces, and clinical software recommendations qualify for statutory exclusion from the device definition, qualify for FDA enforcement discretion (where a product may still meet the statutory definition of a device under FD&C Act § 201(h)(1), but FDA does not intend to enforce applicable regulatory requirements), or remain subject to applicable device requirements, including premarket authorization where required. These are illustrative outcomes, not an exhaustive classification scheme; exemption status and the applicable pathway require a function-specific assessment.

For chief marketing officers, regulatory affairs leads, and digital product managers at wearable, software-as-a-medical-device (SaMD), and medical technology companies, the practical stakes of these revisions are visible in CDRH's 2025–2026 enforcement record. On July 14, 2025, CDRH issued Warning Letter MARCS-CMS 709755 to WHOOP, Inc. after the company launched its Blood Pressure Insights ("BPI") feature on a wrist-worn optical photoplethysmography (PPG) strap [4]. CDRH cited WHOOP's website headlines ("delivering medical-grade health & performance insights", "daily systolic and diastolic blood pressure estimations"), a company blog post linking blood pressure to sleep quality, and the mobile app's color-coded green, yellow, and orange target-range gauge as objective evidence that BPI was an unapproved Class II noninvasive blood pressure measurement system under 21 CFR § 870.1130 (Product Code DXN) [4] [13]. Eleven months later, on June 17, 2026, CDRH issued Close-Out Letter MARCS-CMS 709755 to WHOOP, Inc., explicitly concluding that following WHOOP's modifications to BPI and its labeling, and consistent with the updated January 6, 2026 General Wellness: Policy for Low Risk Devices guidance, FDA does not intend to enforce device statutory and regulatory requirements for BPI as modified [5].

During the same early-2026 enforcement cycle, CDRH issued Warning Letter MARCS-CMS 715068 (February 6, 2026) to ExThera Medical Corporation [6] and Warning Letter MARCS-CMS 719460 (January 29, 2026) to Diasol, Inc. [7]. The ExThera action—following a May 27 to June 4, 2025 Office of Bioresearch Monitoring Inspectorate (OBMI) inspection—demonstrates how CDRH assembles 21 CFR § 801.4 intended-use, unapproved-device (FD&C Act §§ 501(f)(1)(B), 502(o), 502(a)), and investigational-device (21 CFR §§ 812.5(b), 812.7, 812.35(a)(1), 812.40, 812.46(a)) citations across multiple communication and operational layers: website frequently asked questions (extheramedical.com, observed May 29, 2025), Chief Medical Officer Dr. Lakhmir "Mink" Chawla's December 2024 Spotify podcast interview (cited by exact timestamps 56:48 on compassionate-use long COVID brain fog and fatigue and 1:07:38 on expanding to outpatients with cancer, long COVID, chronic viremia, chronic Lyme, and aging), September and November 2024 Vimeo conference and promotional videos (vimeo.com/1014979373 and vimeo.com/1031732539), FDA's prior July 17, 2024 It Has Come to Our Attention (IHCTOA) letter regarding foreign distributor Quadrant Clinical Care's webpage claiming FDA clearance for COVID-19 and sepsis, unapproved April 2024 and unreported November 2024 hospital compassionate/emergency-use shipments and authorizations (which ExThera stated were not used), and an updated internal work instruction (WI-00011, "Use of Unapproved Devices in United States", piloted from WI017) that invoked both the Federal Right to Try Act of 2017 (21 U.S.C. §§ 360bbb-0a–0c, which excludes medical devices altogether) and state "Right to Try" laws (which, where conflicting with applicable Federal law, do not relieve a firm of Federal-law obligations) [6] [11] [12]. Conversely, the Diasol warning letter, issued eight days earlier following a July 21 to August 19, 2025 inspection in Phoenix, Arizona, cited 21 CFR § 807.81(a)(3)(ii) (FD&C Act §§ 501(f)(1)(B), 502(o)) because while Diasol held 510(k) K020231 for a Citric Acid product intended for use with sorbent regenerated dialysis to allow physicians to customize dialysate, that product was not intended for disinfecting hemodialysis machines, yet Diasol marketed 50% and 20% Citric Acid solutions indicated for cleaning, decalcification, and heat disinfection of hemodialysis machines—establishing an unapproved intended-use violation from inspectional and labeling records alone without quoting a single web page or social media post [7] [10].

To ground these legal boundaries in empirical registry data, this report programmatically analyzes two complete federal datasets:

1. The openFDA Device Classification bulk archive (the preserved source record, archived snapshot 2026-09-21, openFDA last_updated=2026-09-14, 7,093 product classification records) [14] [15], which shows that 3,221 product codes (45.41%) require a 510(k) (submission_type_id=1), 501 (7.06%) require Premarket Approval (submission_type_id=2), 2,639 (37.21%) are 510(k) Exempt (submission_type_id=4), and only 306 product codes (4.31%) carry raw submission_type_id=7 (the classification code applied to enforcement-discretion convenience kits and designated sporting/wellness pulse oximeters such as OCH and PGJ) [14] [15].
2. The FDA Warning Letters corpus (the preserved source record, 20260731_full extract, archived snapshot 2026-08-16, 3,643 indexed warning letters issued from 2021-01-04 through 2026-07-23) [16], within which the issuing_office == "Center for Devices and Radiological Health" subset accounts for 220 warning letters overall (6.04%) and 82 warning letters across 2025 (n = 61) and 2026 through 2026-06-15 (n = 21), led by Current Good Manufacturing Practice / Quality System Regulation citations (38 letters, 46.34%), registration and listing failures (12 letters, 14.63%), and three selected IDE / PMA / premarket-clearance metadata subject categories (17 letters combined, 20.73%; representing primary index metadata tags rather than 17 individually verified intended-use letters) [16].

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1. Statutory Architecture of "Intended Use" and Software Exclusions: 21 CFR § 801.4 and FD&C Act Section 520(o)

Every regulatory boundary governing medical device websites, mobile application user interfaces, clinical validation white papers, and executive media appearances rests on the interaction between two federal legal authorities: the definition of a "device" in Section 201(h)(1) of the Federal Food, Drug, and Cosmetic Act (21 U.S.C. § 321(h)(1)) as modified by the software exclusions of Section 520(o) (21 U.S.C. § 360j(o)), and the evidentiary definition of "intended uses" in 21 CFR § 801.4 [1] [2] [8].

1.1 The Evidentiary Breadth of 21 CFR § 801.4 (86 FR 41383)

Under Section 201(h)(1) of the FD&C Act, an instrument, apparatus, implement, machine, contrivance, implant, in vitro reagent, or software function is a regulated medical device if it is "intended for use in the diagnosis of disease or other conditions, or in the cure, mitigation, treatment, or prevention of disease, in man or other animals," or "intended to affect the structure or any function of the body of man or other animals" [1] [3]. Whether a product triggers that statutory threshold depends on its "intended use."

In 21 CFR § 801.4 (current as of October 22, 2026, reflecting the final rule Regulations Regarding "Intended Uses" published at 86 FR 41383 on August 2, 2021, Docket No. FDA-2015-N-2002), FDA defines "intended uses" as the objective intent of the persons legally responsible for the labeling of an article [8] [9]. The regulation specifies five non-exclusive categories of direct and circumstantial evidence from which objective intent is determined:

1. Labeling claims: Statements on the physical device, packaging, instructions for use (IFU), in-app onboarding screens, and product web pages that accompany the product in interstate commerce (FD&C Act § 201(m), 21 U.S.C. § 321(m)) [8] [9];
2. Advertising matter: Paid search copy, social media promotions, trade-show banners, press releases, and consumer or clinician landing pages [3] [8];
3. Oral or written statements by the manufacturer or its representatives: Executive interviews on podcasts, conference podium presentations, webinar recordings, investor or partner slide decks, customer support scripts, and foreign or domestic distributor communications [6] [8];
4. The design or composition of the article: Hardware sensor architecture, algorithm thresholds, user-interface color coding, alarm acoustics, and data-export formats [4] [8] [9]; and
5. The circumstances surrounding the distribution of the article: Target clinical vs. consumer channels, physician ordering workflows, and internal standard operating procedures governing shipment and clinical use [6] [8] [9].

In the August 2, 2021 final rule (86 FR 41383), FDA amended the final sentence of 21 CFR § 801.4 to clarify a long-debated evidentiary point: "provided, however, that a firm would not be regarded as intending an unapproved new use for an approved or cleared device based solely on that firm's knowledge that such device was being prescribed or used by health care providers for such use" [8] [9]. While mere knowledge of off-label physician use does not by itself create a new intended use, the preamble at 86 FR 41383–41396 confirms that FDA evaluates product design features, UI displays, public marketing copy, and representative statements together when assessing whether a firm objectively intends a diagnostic, therapeutic, or disease-mitigation use [9]. Consequently, a disclaimer placed in a website footer or mobile app settings menu—such as "This product is not a medical device and is not intended to diagnose, treat, cure, or prevent any disease"—does not insulate a product if its primary landing page, blog content, or user-interface gauge objectively communicates a clinical diagnostic or disease-management purpose [1] [4] [9].

1.2 Software Exclusions Under FD&C Act Section 520(o) (21 U.S.C. § 360j(o))

Section 520(o)(1) of the FD&C Act excludes five categories of software functions from the device definition when their respective conditions are satisfied. The special override mechanism in section 520(o)(3) applies to categories (C), (D), and (E), not to administrative-support or healthy-lifestyle categories (A) and (B). Two exclusions are especially relevant here: healthy-lifestyle software unrelated to disease under (B), and qualifying HCP clinical decision support under (E). Criterion 1 of the CDS framework comes from the introductory language of (E); the other three correspond to clauses (i)–(iii). They are not four separately numbered statutory subclauses [1] [2] [17].

Healthy-lifestyle software and non-device CDS require separate assessments. The former concerns a function intended to maintain or encourage a healthy lifestyle without a disease-related purpose. The latter requires a function that does not acquire, process, or analyze the specified images or signals; displays, analyzes, or prints qualifying medical information; supports or recommends to an HCP; and enables that HCP to independently review the basis rather than rely primarily on the recommendation for an individual patient's decision [17].

A critical structural distinction separates these two statutory exclusions from FDA's broader enforcement discretion policies. When a software function strictly satisfies Section 520(o)(1)(B) (healthy lifestyle without disease reference) or all four criteria of Section 520(o)(1)(E) (Non-Device CDS), it is not a medical device by statute [1] [2]. Conversely, when a hardware wearable (such as an optical PPG wristband or smart ring), a hardware-plus-software system, or a software function references reducing the risk of or living well with a chronic disease (General Wellness Category 2) [1], logs blood pressure for hypertension patients (MMA Guidance Section V.B) [3], or outputs a single clinically appropriate recommendation to an HCP where only one clinical option exists (CDS Guidance Section IV(3)) [2], the product may still fall within the statutory definition of a device under Section 201(h)(1), where FDA states in its nonbinding policy guidances that it does not intend to enforce premarket notification (510(k)), registration and listing (21 CFR Part 807), or Quality Management System Regulation (21 CFR Part 820) requirements when the product's claims, user interface, and risk profile align with the policy considerations in FDA's guidance [1] [2] [3].

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2. Empirical Baseline: The openFDA Device Classification Landscape (7,093 Product Codes)

Before examining how the January 2026 General Wellness and CDS guidances treat specific physiological parameters and software algorithms, regulatory and commercial teams need an exact quantitative view of how FDA classifies medical devices across its product-code taxonomy. Using the openFDA Device Classification bulk archive (the preserved source record, archived snapshot 2026-09-21, openFDA last_updated=2026-09-14, SHA-256: 5740b45d0b3d35f6182d5e663b2b1485496323c406122a7eba3790e61a379903) [14] and FDA's official field reference Device Classification Reference (deviceclass_reference.pdf) [15], we aggregated all 7,093 product classification records by device_class, submission_type_id, Good Manufacturing Practice exemption status (gmp_exempt_flag), and Third-Party 510(k) review eligibility (third_party_flag).

2.1 Distribution of All 7,093 Product Codes Across Device Classes and Submission Types

In deviceclass_reference.pdf, FDA defines six device_class codes: 1 = Class I (low to moderate risk: general controls), 2 = Class II (moderate to high risk: general controls and special controls), 3 = Class III (high risk: general controls and Premarket Approval), U = Unclassified, N = Not classified, and F (represented as lowercase f in the JSON export) = Humanitarian Device Exemption (HDE) [14] [15]. For submission_type_id, deviceclass_reference.pdf documents 1 = 510(K), 2 = PMA, 3 = Contact ODE, and 4 = 510(K) Exempt [15]. In the 2026-09-21 openFDA JSON payload, four additional raw submission_type_id values appear outside the 1–4 table in deviceclass_reference.pdf: raw code 7 (306 product codes, whose embedded definition strings in the dataset describe enforcement-discretion convenience kits or sporting/wellness devices), raw code 6 (57 product codes, concentrated in device_class=f), raw code 8 (42 product codes), and blank "" (214 product codes, concentrated in device_class=N) [14] [15]. Because automated retrieval of the interactive web search form classification.cfm returned an Akamai request-filtering redirect during scripted verification, Table 1 reports the verified deviceclass_reference.pdf labels alongside the exact raw submission_type_id codes from the JSON payload [14] [15].

Table 1. Distribution of all 7,093 FDA product classification records across device_class (1=Class I, 2=Class II, 3=Class III, U=Unclassified, N=Not classified, f=HDE per deviceclass_reference.pdf) and submission_type_id (1=510(K), 2=PMA, 3=Contact ODE, 4=510(K) Exempt per deviceclass_reference.pdf, plus raw codes 6, 7, 8, and blank "") in the openFDA Device Classification bulk archive (the preserved source record, snapshot 2026-09-21, openFDA last_updated=2026-09-14).

The classification table is a taxonomy, not a sample of marketed products or a probability model. Class II accounts for 3,640 of 7,093 codes (51.32%); 3,000 of those Class II codes have submission type 1, and 484 have type 4. These counts do not imply that a newly designed wearable has an 82.42% chance of needing a 510(k), or that crossing a wellness claim boundary almost invariably produces Class II status. Classification depends on the actual function, intended use, applicable regulation, and exemptions [14] [15].

Similarly, 306 records carry raw submission type 7. Named product definitions can help investigate particular sporting or wellness functions, but the count does not estimate the prevalence of general-wellness products or non-device software, many of which are outside the purpose of this device classification table. The registry does not provide a denominator for products marketed without codes. A GMP-exemption flag addresses that flag's scope; it does not by itself establish registration, listing, reporting, or labeling obligations. The classification parts' .9 limitations concern premarket-notification exemptions, not a universal limitation governing every other regulatory exemption [13] [14].

2.2 Product Code Stratification Across Focal Physiological Sensing, SaMD, and Enforcement Regulations

To connect the registry structure directly to the January 2026 guidances and the 2025–2026 CDRH warning letters, Table 2 extracts the product-code records for the exact regulations cited in FDA's General Wellness guidance (21 CFR §§ 870.1130, 870.2700, 870.2300, 870.2340, 862.1345, 862.1355, 878.4635, 876.5020), the Device Software / MMA and CDS guidances (21 CFR §§ 870.2785, 892.2050), and the WHOOP and Diasol warning letters (21 CFR §§ 870.1130, 876.5665, 876.5820) [1] [2] [3] [4] [7] [13] [14]. In interpreting Table 2, note that openfda.k_number length is the count of linked K-number identifiers in the harmonized openFDA classification record (not a proven complete historical clearance total or commercial sales volume), and openfda.registration_number length is the count of linked facility registration identifiers in the harmonized classification record (not a count of active commercial device listings) [14] [15].

Table 2. Product code classifications, submission_type_id values, linked K-number identifier array lengths (openfda.k_number length), and linked registration identifier array lengths (openfda.registration_number length) across focal regulations cited in FDA's January 2026 General Wellness and CDS guidances, the Device Software/MMA guidance, and 2025–2026 CDRH warning letters (the preserved source record, snapshot 2026-09-21). Array lengths reflect linked identifiers in the harmonized openFDA classification record, not complete historical clearances or active device listings.

The focal codes illustrate why intended use and function need to be examined together. The oximetry regulation has clinical codes such as DQA and product definitions for sporting/aviation or wellness use such as OCH and PGJ. Optical camera vital-sign measurement and radiological image processing likewise have their own regulated classifications. Linked identifiers are a navigation aid for finding records; they are not complete counts of active products or annual clearances [13] [14].

The blood-pressure regulation's two codes in this snapshot, DXN and QYF, both have submission type 1. That does not prove every optical blood-pressure feature must use those codes, nor explain why FDA revised its wellness guidance. The later WHOOP close-out is specific to the modified BPI feature and its labeling. For continuous glucose monitors, skin penetration is relevant to the wellness policy's low-risk boundary; invasiveness alone does not determine a product's classification, clearance status, or every applicable requirement [1] [5].

For image- or signal-processing software, failure to satisfy the first CDS criterion removes reliance on that particular exclusion. It does not complete the entire regulatory analysis. The team still needs to evaluate the device definition, other exclusions, and applicable policies. A website's comparison table should reflect that function-specific conclusion rather than infer status from a neighboring product code [2] [17].

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3. FDA's January 6, 2026 General Wellness Final Guidance (Document 1300013) and the WHOOP Warning-to-Close-Out Enforcement Arc

The most consequential 2026 policy development for wearable hardware, smart ring, wrist strap, and consumer health app teams is FDA's superseding Final Guidance General Wellness: Policy for Low Risk Devices (Document Number 1300013, issued January 6, 2026) [1] and its direct application in resolving the WHOOP, Inc. enforcement action (MARCS-CMS 709755) between July 14, 2025 and June 17, 2026 [4] [5].

3.1 The Two General Wellness Intended-Use Categories (Section III, printed pp. 3–5)

In Section III of the January 6, 2026 guidance (printed pp. 3–5), FDA defines a "general wellness product" as a product that meets both low-risk criteria (Section IV) and one of two intended-use categories [1]:

1. Category 1 — Disease-Free Healthy Activity Claims (Section III, printed pp. 3–4): An intended use that relates to maintaining or encouraging a general state of health or a healthy activity, without any reference to diseases or conditions [1]. FDA enumerates seven qualifying wellness domains: (i) weight management (e.g., promoting or maintaining a healthy weight, encouraging healthy eating, or assisting with weight loss goals), (ii) physical fitness, including products intended for recreational use (e.g., logging, tracking, or trending exercise activity, measuring aerobic fitness, or improving endurance, strength, or coordination), (iii) relaxation or stress management, (iv) mental acuity (e.g., concentration, problem-solving, multitasking, or logic), (v) self-esteem (e.g., cosmetic functions making claims related only to self-esteem), (vi) sleep management (e.g., tracking sleep trends), and (vii) sexual function [1]. Because Category 1 claims make zero reference to any clinical condition, software functions limited strictly to Category 1 are excluded from the statutory device definition under FD&C Act Section 520(o)(1)(B) (21 U.S.C. § 360j(o)(1)(B)) [1].
2. Category 2 — Chronic Disease Risk-Reduction and Living-Well Claims (Section III, printed pp. 4–5): An intended use that relates the role of a healthy lifestyle with helping to reduce the risk or impact of certain chronic diseases or conditions, comprised of two subcategories: (1) intended uses to promote, track, and/or encourage choice(s) which, as part of a healthy lifestyle, may help to reduce the risk of certain chronic diseases or conditions; and (2) intended uses to promote, track, and/or encourage choice(s) which, as part of a healthy lifestyle, may help living well with certain chronic diseases or conditions [1]. FDA specifies that both subcategories should only be based on references where it is well understood and generally accepted—as described in peer-reviewed scientific publications or official statements made by healthcare professional organizations (such as the American Medical Association, American Heart Association, American Association of Clinical Endocrinologists, or American College of Rheumatology)—that healthy lifestyle choices may play an important role in health outcomes for that chronic disease or condition (naming heart disease, high blood pressure, and type 2 diabetes as examples) [1].

3.2 The January 6, 2026 Addition: Non-Invasive Sensing of Blood Pressure, SpO2, Blood Glucose, and HRV (Section III, printed pp. 5–6)

The decisive addition in the January 6, 2026 guidance (Section III, printed pp. 5–6) addresses products that use non-invasive sensing—specifically naming optical sensing—to estimate, infer, or output physiologic parameters (specifically naming blood pressure, oxygen saturation, blood glucose, and heart rate variability) [1].

On printed page 5 of the January 6, 2026 guidance, FDA states that it may consider certain products that use non-invasive sensing (e.g., optical sensing) to estimate, infer, or output physiologic parameters (e.g., blood pressure, oxygen saturation, blood glucose, heart rate variability) to be general wellness products when such outputs are intended solely for wellness uses, and provided they meet all six criteria [1]:

1. are non-invasive and not-implanted;
2. do not involve an intervention or technology that may pose a risk to the safety of users or other persons if specific regulatory controls are not applied;
3. are not intended for the diagnosis, cure, mitigation, prevention, or treatment of a disease or condition;
4. are not intended to substitute for an FDA-authorized, cleared, or approved device;
5. do not include claims, functionality, or outputs that prompt or guide specific clinical action or medical management; and
6. do not include values that mimic those used clinically unless validated (e.g. manufacturer testing, peer-reviewed clinical literature) to reflect those values [1].

On printed page 6, FDA states that products meeting those six criteria "may display values, ranges, trends, baselines, or longitudinal summaries, and may contextualize these outputs in relation to sleep, activity, stress, recovery, or similar wellness domains" [1]. Conversely, products are not general wellness products when they are intended to measure, estimate, or report physiologic values for medical or clinical purposes, including screening, diagnosis, monitoring, alerting, or management of a disease or condition—such as blood pressure monitors or sphygmomanometers, fingerstick blood glucose meters and continuous glucose monitoring systems, electrocardiogram recording and analysis devices, and any product intended to provide outputs used to make treatment decisions (e.g., medication dosing) [1].

Immediately following that boundary (Section III, printed p. 6), FDA enumerates five explicit disqualifiers: products are not general wellness products if their labeling, advertising, user interface, or functionality includes any of the following [1]:

1. references to specific diseases, clinical conditions, or diagnostic thresholds;
2. alerts, alarms, or prompts that recommend or require specific clinical action or medical management;
3. treatment guidance intended to inform or direct medical management;
4. claims of clinical equivalence, clinical accuracy, medical or clinical grade, or substitution for an FDA-authorized, cleared, or approved medical device; or
5. intended-use statements that explicitly target diagnosis, screening, monitoring, or management of a disease or condition [1].

Additionally, on printed page 6 of the January 6, 2026 guidance, FDA clarifies that a product may be considered a general wellness product even if it includes a notification informing a user that evaluation by a healthcare professional may be helpful when outputs fall outside ranges appropriate for general wellness use, provided that such notifications satisfy all four conditions (Section III, printed p. 6):

1. do not identify or name a specific disease or medical condition;
2. do not characterize the output as abnormal, pathological, or diagnostic;
3. do not include clinical thresholds, diagnoses, or treatment recommendations; and
4. do not provide ongoing alerts or monitoring intended to manage a disease or condition [1].

Finally, FDA states at the close of Section III (printed p. 6) that it expects a product intended for general wellness use to have labeling—including instructions for use, user-facing claims, promotional materials, and marketing communications—that is consistent with, and does not exceed, the product's stated intended use [1].

3.3 Low-Risk Technology Boundaries (Section IV, printed pp. 6–7) and Illustrative Examples 5, 7, 8, and 9 (Section V, printed pp. 8–10)

Even if a product's claims stay within general wellness, Section IV (printed pp. 6–7) states that CDRH's general wellness policy applies only to general wellness products that are low risk [1]. If the answer to any of the following three questions is "YES," the product is not low risk and is not covered by the guidance:

1. Is the product invasive? (Defined in Footnote 9 on printed p. 6 as "penetrates or pierces the skin or mucous membranes of the body.")
2. Is the product implanted?
3. Does the product involve an intervention or technology that may pose a risk to the safety of users and other persons if specific regulatory controls are not applied, such as risks from lasers or radiation exposure? [1]

In Section IV (printed pp. 6–7), FDA notes that whether a device is classified as Class I under Section 513(a)(1) of the FD&C Act does not necessarily mean it is "low risk" for purposes of the guidance (Footnote 8 on printed p. 6), and recommends considering whether CDRH actively regulates products of the same type (printed p. 7) [1]. FDA cites two specific codified regulations to illustrate products that are not low risk:

• External Penile Rigidity Devices (21 CFR § 876.5020, Product Code LKY): Actively regulated under 21 CFR § 876.5020 as Class II devices exempt from premarket notification (submission_type_id=4, 87 linked K-numbers and 48 linked registration identifiers) with special controls addressing risks of tissue injury, trauma, or infection [1] [13] [14].
• Sunlamp Products (21 CFR § 878.4635, Product Codes LEJ, SGZ): Promoted for tanning purposes, but excluded from low-risk status due to ultraviolet radiation safety risks including increased risk of skin cancer, and regulated as Class II special-controls devices (510(k) under submission_type_id=1, 81 linked K-numbers for LEJ), with mandatory black-box warnings on the device and contraindication/skin-cancer warnings required on all consumer-directed catalogs, specification sheets, descriptive brochures, and Web pages (21 CFR § 878.4635(b)(6)(ii)) [1] [13] [14].

In Section V (printed pp. 8–10), FDA provides nine illustrative examples (Examples 1–9), four of which (Examples 5, 7, 8, and 9 on printed pp. 9–10) directly address physiological sensing wearables in 2026 [1]:

• Illustrative Example 5 (printed p. 9) — Portable Product Monitoring Pulse Rate and/or Oxygen Saturation During Exercise and Hiking: A portable product intended to monitor the pulse rate and/or oxygen saturation of users during exercise and hiking. Because the claim relates only to exercise and hiking without referring to a disease or medical condition and the technology does not pose a safety risk requiring specific regulatory controls, it meets both factors for a low-risk general wellness product (aligning with raw code 7 product codes OCH and PGJ under 21 CFR § 870.2700) [1] [14].
• Illustrative Example 7 (printed p. 9) — Wrist-Worn PPG Wearable Outputting Sleep, Pulse Rate, and Blood Pressure for Activity and Recovery: A wrist-worn wearable product intended to assess activity and recovery that outputs multiple biomarkers, among which are hours slept, sleep quality, pulse rate, and blood pressure, where sleep is measured via an accelerometer and pulse rate and blood pressure are measured via a photoplethysmogram (PPG). FDA states that this product meets both factors for a low-risk general wellness product, provided the product has validated values for blood pressure, while adding the explicit Note: "However, if the claims made about any of the product's functionality implied the product's use in a medical or clinical context, the product would not be a low risk general wellness product" [1].
• Illustrative Example 8 (printed pp. 9–10) — Minimally Invasive Microneedle Glucose Wearable for Nutritional Impacts: A wearable product intended to provide estimations of blood glucose for monitoring nutritional impacts using minimally invasive microneedle technology, explicitly contraindicated for diabetics and pre-diabetics and marketed to help users better understand their insulin response to certain foods. FDA states that while the claim is a general wellness claim (provided it has validated values for blood glucose), the product penetrates the stratum corneum and is therefore not a low-risk general wellness product [1]—explaining why over-the-counter continuous glucose monitors (SAF and SBH under 21 CFR § 862.1355) require Class II premarket notification (submission_type_id=1) [1] [14].
• Illustrative Example 9 (printed p. 10) — Non-Invasive Athlete Wearable Monitoring Electrolyte Balance, Lactate, and Hemoglobin: A non-invasive wearable product advertised toward elite athletes to monitor electrolyte balance, lactate, and hemoglobin, labeled for use in an exercise/fitness context only, displaying values from cleared devices or ranges from the wearable's optical sensor, and disclaimed for diagnosing any condition or disorder. FDA concludes that it meets both factors for a low-risk general wellness product, provided it has validated values for these parameters [1].

3.4 Case Study: WHOOP, Inc. Warning Letter (July 14, 2025) to Close-Out Letter (June 17, 2026)

The regulatory trajectory of WHOOP, Inc. (MARCS-CMS 709755) provides a real-world case study demonstrating how CDRH enforced the pre-2026 blood pressure boundary and how a wearable manufacturer achieved close-out under the January 6, 2026 General Wellness guidance [4] [5].

On July 14, 2025, CDRH's Office of Product Evaluation and Quality (OPEQ) issued Warning Letter MARCS-CMS 709755 to WHOOP, Inc. regarding its Blood Pressure Insights ("BPI") feature [4]. Following CDRH teleconferences with WHOOP on May 15, 2025, and May 27, 2025, and WHOOP's June 2, 2025 letter asserting that BPI was not a device under FD&C Act Section 201(h) and was excluded under Section 520(o)(1)(B), CDRH reviewed WHOOP's website (www.whoop.com/us/en/, last reviewed May 28, 2025) and associated article "WHOOP Delivers Innovative Blood Pressure Insights for a Deeper Look at Your Well-Being" (last reviewed May 28, 2025), citing four specific evidentiary elements under 21 CFR § 801.4 [4]:

1. Website "Medical-Grade" and Blood Pressure Estimation Claims: WHOOP's website described BPI as providing "daily systolic and diastolic blood pressure estimations, offering members a new way to understand how blood pressure affects their performance and well-being," and listed BPI as an example of how WHOOP is "delivering medical-grade health & performance insights" [4].
2. Causal Link Between Blood Pressure and Sleep in Associated Article: WHOOP's associated article stated that "the impact of blood pressure on sleep, recovery, and performance are not well understood or widely studied," and WHOOP's statements indicated that "Higher blood pressure may be an indicator of poor sleep," which CDRH cited as implying a causal link between a user's blood pressure measurement and wellness results and identifying "higher blood pressure" [4].
3. Color-Coded Target-Range UI Gauge: By design, BPI output a blood pressure measurement (including a daily blood pressure range and midpoint estimation) on a gauge that uses green, yellow, and orange color-coding to indicate a target blood pressure range [4].
4. Inherent Clinical Association Under 21 CFR § 870.1130 (DXN), Inefficacy of Disclaimers, and Clinical Risk of Falsely Low Readings: Under the 2019 wellness policy then in effect, CDRH stated that blood pressure measurement or estimation is inherently associated with the diagnosis of hypo- and hypertension (21 CFR § 870.1130, Product Code DXN), that BPI's disclaimers were insufficient to outweigh the product's design and intent (as demonstrated by evidence of individuals using BPI to monitor their hypertension), and that under the 2019 guidance's Category 2 analysis, blood pressure estimation was not low risk because falsely low readings could inappropriately reassure a user with hypertension, cause elevated readings at a doctor's office to be misinterpreted as white coat hypertension (2017 ACC/AHA high blood pressure guideline), and delay treatment needed to prevent stroke, heart attack, heart failure, or kidney failure [4].

The January 2026 guidance addresses non-invasive sensing, wellness context, clinical-looking values, and disqualifying clinical claims. These topics overlap with issues in the earlier WHOOP letter. That overlap does not establish that WHOOP caused the policy revision or that the agency wrote the guidance to resolve this particular case. The guidance should be read on its own terms, and the later close-out on its expressly limited scope [1] [4] [5].

FDA's June 17, 2026 close-out states that, following changes to BPI and its labeling and consistent with the updated wellness guidance, FDA does not intend to enforce device requirements for BPI as modified. The letter expressly excludes other products, features, and subsequent modifications. It is not a marketing authorization, clinical validation report, or generally transferable design recipe. The index's June 23 date should not replace the letter's June 17 issue date [5] [16].

Policy inclusion also does not establish that a particular sensor is accurate or that a product is safe or effective. FDA's separate safety communication warns against using smartwatches or smart rings that claim to measure blood glucose without piercing the skin. A commercial team should not present the wellness guidance's examples as overriding that warning or as agency endorsement of an unverified glucose claim. Validation evidence, intended use, and the precise policy conditions remain separate questions [1] [18].

For wearable and consumer digital health companies—including hypothetical composite commercial profiles such as Company A (a hypothetical consumer-plus-professional wearable manufacturer marketing both wellness fitness bands and 510(k)-cleared ECG/oximetry hardware on the same domain) and Company B (a hypothetical AI-enabled smart wearable developer)—the WHOOP Warning-to-Close-Out arc illustrates how CDRH applies its nonbinding January 6, 2026 General Wellness policy in practice: when a manufacturer seeks to market non-invasive optical estimation of blood pressure, SpO2, blood glucose, or HRV under FDA's January 6, 2026 General Wellness enforcement-discretion policy, website copy should omit "medical-grade" / "clinical-grade" / "clinical equivalence" claims, UI displays should avoid clinical diagnostic thresholds and disease-management alerts, validation data should substantiate any values mimicking clinical values, and product pages should separate wellness features from FDA-authorized medical devices [1] [4] [5].

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4. Software Claims Governance: FDA's January 29, 2026 Clinical Decision Support Guidance (GUI01400062) and the Device Software / MMA Guidance (Document 1741)

While the January 6, 2026 General Wellness guidance governs consumer-facing and lifestyle-contextualized products, B2B medical software vendors, hospital informatics teams, and connected-device platforms must align their website claims and software documentation with FDA's January 29, 2026 superseding Final Guidance Clinical Decision Support Software (Document Number GUI01400062) [2] and FDA's Final Guidance Policy for Device Software Functions and Mobile Medical Applications (Document Number 1741, September 28, 2022, with February 2, 2024 QMSR cover note) [3].

4.1 The Four Statutory Non-Device CDS Criteria and the January 29, 2026 Revision (Document GUI01400062)

To rely on the statutory non-device CDS exclusion in section 520(o)(1)(E), assess all four criteria at the software-function level. Failure of one criterion means the function cannot rely on that exclusion; it does not automatically prove that the function is a regulated device. Consider the statutory device definition, other potentially applicable exclusions, and FDA's enforcement policies. FDA's single-recommendation policy is a distinct enforcement-discretion discussion for a function for which only one option is clinically appropriate and that otherwise meets the criteria. Do not label that policy as statutory non-device status [2] [17].

1. Criterion 1 (Section IV(1), pp. 7–9) — Exclusion of Medical Images, IVD Signals, and Signal Acquisition Patterns: Software fails Criterion 1 if it acquires, processes, or analyzes a medical image (e.g., CT, MRI, ultrasound, X-ray, or pathology/dermatology image under 21 CFR § 892.2050, Product Codes LLZ and QIH), a signal from an in vitro diagnostic device, or a pattern or signal from a signal acquisition system [2] [14]. In the January 29, 2026 guidance (pp. 7–9), FDA distinguishes between: - Inputs outside the particular CDS exclusion: Multiple, sequential, or repeated measurements of a signal or from a signal acquisition system—such as raw electrocardiograph (ECG) waveforms and QRS complexes (21 CFR §§ 870.2340, 870.2345), Next Generation Sequencing (NGS) variant call format (VCF) files, continuous glucose monitor (CGM) readings over time, photoplethysmograph (PPG) pulse waveforms (21 CFR § 870.2790), video-camera optical pulse signals (21 CFR §§ 870.2785, 870.2786), or continuous bedside monitor data streams (21 CFR § 870.2300, Product Codes DRT, MWI, PLB) [2] [13] [14]. - Qualifying Discrete Medical Information (Criterion 2 Inputs): Discrete, episodic, or intermittent point-in-time physiological measurements or test results already generated by a legally marketed device or clinical laboratory—such as a blood pressure result ("120/80 mmHg") from a legally marketed device, a lab test result ("potassium level of 4.0 mmol/L or glucose level of 95 mg/dL") in an electronic health record (EHR), an ECG report annotated by an HCP ("the patient shows signs of Atrial Fibrillation"), or a radiology report ("a BIRADS category 4 lesion is present") [2].
2. Criterion 2 (Section IV(2), pp. 9–10) — Display, Analysis, or Printing of Medical Information: The software must use discrete patient-specific medical information (such as demographic information, symptoms, certain test results, or patient discharge summaries) and/or other medical information from well-understood and accepted sources (such as clinical practice guidelines, peer-reviewed clinical studies, textbooks, FDA-required drug/device labeling, and government agency recommendations) [2].
3. Criterion 3 (Section IV(3), pp. 10–14) — Recommendations to a Health Care Professional and the January 2026 Single-Recommendation Enforcement Discretion Policy: Criterion 3 establishes three strict boundaries for marketing and product design: - HCP-Only Recipient: Statutory Non-Device CDS must provide recommendations to a health care professional (HCP), not to a patient or lay caregiver [2]. Patient- or caregiver-directed recommendations do not satisfy this HCP-specific exclusion and should be evaluated under FDA's existing digital health policies, such as the General Wellness guidance [1] or the Device Software / MMA guidance [3]. - Enhancing Rather Than Replacing or Directing HCP Judgment: Non-Device CDS provides condition-, disease-, and/or patient-specific information and options (such as a list or prioritized list of preventive, diagnostic, or treatment options, or follow-up/next-step options) to an HCP to enhance, inform, and/or influence a health care decision, without providing a specific directive intended to replace the HCP's judgment [2]. - The Single-Recommendation Enforcement Discretion Policy (Section IV(3), pp. 10–12): In Section IV(3) (pp. 10–11), FDA states that if only one option is clinically appropriate and the software function otherwise meets all criteria under section 520(o)(1)(E), FDA intends to exercise enforcement discretion (meaning that FDA does not intend to enforce requirements under the FD&C Act) for such functions [2]. On pages 11–12, FDA illustrates this enforcement-discretion policy with seven positive examples—such as predicting risk of future cardiovascular events from weight, smoking status, blood pressure, and BNP IVD test results; recommending a specific FDA-approved antibiotic agent based on symptoms, recent hospitalizations, and prior antibiotic exposure; generating a proposed clinical summary and specific guideline-based diagnostic recommendation from a radiologist's clinical findings; or classifying chronic low back pain into a single recommended care pathway—contrasted against device software functions that remain the focus of FDA oversight because they predict a cardiovascular event in the next 24 hours, guide immediate escalation of care for acute trauma or intraoperative mortality, or analyze raw PET scan images, spectroscopy data, or unestablished genomic inputs [2].
4. Criterion 4 (Section IV(4), pp. 14–16) — Enabling Independent HCP Review of the Basis and Avoiding Time-Critical Automation Bias: Under Section 520(o)(1)(E)(iii), the software function must be intended to enable HCPs to independently review the basis for the recommendations so that they do not rely primarily on such recommendations [2]. FDA explicitly notes (p. 14) that sponsors may use alternative approaches so long as their approach enables independent HCP review, and provides four nonbinding software and labeling recommendations (a through d on pp. 14–15) [2]: - (a) Purpose, User, Population, and Non-Time-Critical Task: Clearly identify the intended use, intended HCP user, and intended patient population. FDA does not consider software functions intended for a critical, time-sensitive task or decision to meet Criterion 4, because in urgent situations automation bias increases and an HCP is unlikely to have sufficient time to independently review the basis (pp. 14–16, citing M.L. Cummings, 2004; compare acute stroke/sepsis alarms in Section V.C Example 11 on p. 22 and cardiovascular machine-learning notification software regulated under 21 CFR § 870.2380, 91 FR 57787, Sept. 11, 2026) [2] [13]; - (b) Required Input Medical Information: Identify required input medical information with plain-language instructions on how inputs should be obtained, their relevance, and data quality requirements [2]; - (c) Plain-Language Algorithm Development and Validation Description: Provide a summary of the general logic or methods relied upon (e.g., meta-analysis, expert panel, statistical modeling, AI/ML techniques), a description of the data relied upon (so the HCP can assess patient population representativeness and whether independent development and validation datasets were used, as illustrated in Section V.C Example 31 on pp. 25–26), and a description of clinical validation study results and sub-population performance limitations [2]; and - (d) Patient-Specific Context and Knowns/Unknowns: Provide the HCP output alongside relevant patient-specific information and knowns/unknowns (such as missing, corrupted, or unexpected input data values) [2].

4.2 Multiple Software Functions on One Platform (Document 1741 and GUI01400062)

In both the Device Software Functions and Mobile Medical Applications guidance (Document 1741, Section I and Section V, pp. 2–3, 10–11) [3] and the Clinical Decision Support Software guidance (Document GUI01400062, Section I and Section III, pp. 5–6) [2], FDA explains how Section 520(o)(2) of the FD&C Act (21 U.S.C. § 360j(o)(2)) applies to products with multiple functions (containing at least one non-device software function excluded under Section 520(o)(1) and at least one regulated device function):

• Under Section 520(o)(2) of the FD&C Act, FDA does not regulate a software function excluded under Section 520(o)(1) (such as a Category 1 healthy-lifestyle software function under Section 520(o)(1)(B) or a Criterion 1–4 Non-Device CDS function under Section 520(o)(1)(E)) as a device. However, Section 520(o)(2) expressly authorizes FDA, when evaluating the regulated device function (such as a Class II 510(k)-cleared OTC ECG arrhythmia detector under 21 CFR § 870.2345 or PPG irregular-rhythm software under 21 CFR § 870.2790), to assess the impact that the non-device software function(s) have on the safety and effectiveness of the device function(s) [2] [3] [13]. An adverse interaction does not convert the statutory non-device function itself into a regulated device; rather, it bears directly on whether the regulated device function is safe and effective for premarket clearance or approval.
• Consequently, during premarket review of the regulated device function, FDA may assess the impact of other functions, including relevant shared resources and interfaces, when evaluating the device function; a manufacturer should examine whether non-device functions could degrade the performance of the regulated device function or cause users to misinterpret unregulated wellness outputs as cleared diagnostic results [19].
• On public websites—illustrated by hypothetical composite MedTech scenarios such as Company A (a hypothetical firm marketing both 510(k)-cleared patient monitors and consumer wellness wearables on one domain) and Company C (a hypothetical multi-module diagnostic and monitoring platform)—applying a blanket "FDA-Cleared" headline across an entire multi-function product family without function-level attribution creates substantial misleading-claim and intended-use risk under 21 CFR § 801.4, 21 CFR § 807.97, and FD&C Act §§ 502(a), 502(o) [3] [8] [10].

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5. Multi-Channel Intended-Use Enforcement in 2025–2026: Empirical Warning Letter Trajectory and the ExThera vs. Diasol Contrast

To understand how CDRH enforces intended-use and premarket-clearance boundaries across digital, media, and operational channels, we analyzed the complete FDA Warning Letters corpus (the preserved source record, 20260731_full extract, archived snapshot 2026-08-16, SHA-256: 8b33857bb2f56f6fb0377d48ade5d6f7d0897790a04b5fd98c625c6684abdbeb) [16] alongside the full official texts of CDRH's 2025–2026 warning letters to WHOOP, Inc. (MARCS-CMS 709755, July 14, 2025, with Close-Out Letter June 17, 2026) [4] [5], ExThera Medical Corporation (MARCS-CMS 715068, February 6, 2026) [6], and Diasol, Inc. (MARCS-CMS 719460, January 29, 2026) [7].

5.1 Quantitative Trajectory of FDA and CDRH Warning Letters (2021–2026)

Across the entire 20260731_full warning-letter archive (3,643 indexed letters with letter_issue_date spanning 2021-01-04 through 2026-07-23 and posted_date through 2026-07-28), enforcement volume is distributed across FDA product centers and field import/inspection divisions, led all-time by the Center for Tobacco Products (1,204 letters), the Center for Drug Evaluation and Research (582 under "Center for Drug Evaluation and Research (CDER)" plus 344 under "Center for Drug Evaluation and Research | CDER"), and the "Center for Devices and Radiological Health" (220 letters, 6.04% of all indexed letters) [16].

Two methodological scope constraints must be kept explicit when interpreting the issuing_office == "Center for Devices and Radiological Health" subset (n = 220 across 2021–2026; n = 82 across 2025–2026, with CDRH letter_issue_date spanning 2021-01-07 through 2026-06-15 and posted_date through 2026-07-22):

1. Issuing-Office String Scope: Filtering by issuing_office == "Center for Devices and Radiological Health" captures only warning letters issued directly under that exact center string (n = 220); it does not include device-related warning letters issued under the Office of Inspections and Investigations (50 letters across 2021–2026; 49 in 2025–2026), import divisions (Division of Southwest Imports, Division of West Coast Imports, Division of Northeast Imports), or combination-product letters issued by CDER or CBER [16].
2. Descriptive Snapshot Close-Out Truncation: The closeout_letter column in the 20260731_full snapshot records whether a close-out date had been posted by the extract cutoff. Because warning-letter remediation, follow-up verification inspections, and FDA close-out reviews unfold over variable multi-month timelines, more recent issue cohorts (2024, 2025, and 2026) have had substantially shorter follow-up windows than 2021–2023 cohorts. Snapshot close-out fractions are therefore descriptive point-in-time counts subject to right-truncation, not longitudinal resolution probabilities or proof of shifting agency leniency [16].

Table 3. Annual distribution of all 3,643 indexed FDA warning letters (letter_issue_date through 2026-07-23, posted_date through 2026-07-28) and the issuing_office == "Center for Devices and Radiological Health" subset (letter_issue_date through 2026-06-15, posted_date through 2026-07-22) in the preserved source record (20260731_full extract, archived snapshot 2026-08-16). CDRH-office matching reflects only letters issued directly under that office string, and snapshot close-out counts reflect unequal follow-up windows rather than longitudinal resolution rates.

Within the 82 warning letters issued directly by the "Center for Devices and Radiological Health" across 2025 (n = 61) and 2026 through 2026-06-15 (n = 21), Table 4 tabulates the primary subject classifications recorded in the index [16].

Table 4. Primary subject classifications across all 82 warning letters in the issuing_office == "Center for Devices and Radiological Health" subset issued in 2025 (n = 61) and 2026 through 2026-06-15 (n = 21) in the preserved source record (20260731_full extract, archived snapshot 2026-08-16).

As Table 4 shows, while manufacturing quality system violations (CGMP/QSR/Medical Devices/Adulterated, 38 letters, 46.34%) and establishment registration/listing failures (Failure to Register and List/Misbranded, 12 letters, 14.63%) represent the two largest individual categories in the 2025–2026 CDRH subset, three selected IDE, PMA, and premarket-clearance metadata subject categories account for 17 letters (20.73%) in the index (representing the primary metadata subject strings assigned to those letters in warning_letters_all.jsonl rather than 17 individually verified intended-use enforcement cases):

• Investigational Device Exemptions (IDE)/Premarket Approval Application (PMA) Adulterated Device (9 letters, 10.98%);
• Medical Device/Adulterated/Misbranded/Lacks PMA and/or 510(k) (4 letters, 4.88%); and
• Investigational Device Exemptions (IDE)/Premarket Approval Application (PMA) (4 letters, 4.88%)—the exact subject classification assigned to WHOOP, Inc. (07/14/2025), Diasol, Inc. (01/29/2026), and ExThera Medical Corporation (02/06/2026) [4] [6] [7] [16].

Notice also in Table 3 that WHOOP, Inc. (issued 07/14/2025, closeout_date 06/23/2026) is one of the 13 CDRH warning letters from the 2025 cohort (21.31%) that had already achieved a posted close-out letter by the 20260731_full snapshot cutoff [5] [16].

5.2 Deep-Dive Case Study 1: ExThera Medical Corporation (MARCS-CMS 715068, February 6, 2026) — Multi-Channel Intended-Use and IDE Promotion Evidence

CDRH's February 6, 2026 Warning Letter to ExThera Medical Corporation (MARCS-CMS 715068, posted February 24, 2026, addressed to CEO Erin R. Borger in Martinez, California) is a landmark enforcement document for life-sciences marketing, clinical affairs, and legal teams because it illustrates how FDA's Office of Bioresearch Monitoring Inspectorate (OBMI) combines physical inspectional records from a May 27, 2025 to June 4, 2025 BIMO inspection with multi-channel digital surveillance under 21 CFR § 801.4 and 21 CFR Part 812 [6] [8] [11].

The OBMI inspection examined ExThera's activities as the study sponsor of two significant risk Investigational Device Exemption (IDE) clinical trials:

1. The Purify Study (IDE G210074, "Blood Purification for the Treatment of Critically Ill Patients with Pathogen Associated Shock: A Multicenter, Randomized Controlled Feasibility Trial") for the Seraph 100 Microbind Affinity Blood Filter; and
2. The Oscar Study (IDE G230144, "Prospective Single-Arm Feasibility Study to Determine the Capacity of the Onco-Seraph 100 Microbind Affinity Blood Filter (Onco-Seraph 100) to Remove Circulating Tumor Cells from the Blood of Patients with Metastatic Pancreatic Ductal Adenocarcinoma") for the Onco-Seraph 100 (also called the ONCObind Seraph 100) [6].

The warning letter describes the absence of an approved PMA, clearance, or appropriate IDE for the device as described and marketed. The historical authorization context matters: FDA issued EUA200165 for specified COVID-19 emergency use on April 17, 2020, and revoked it effective November 24, 2025 following the firm's request. An EUA is different from approval or clearance, and its limited scope did not authorize every subsequently promoted indication. The revocation should not be presented as a penalty imposed by the later warning letter [6] [20] [21].

For commercial governance, the letter's significance is the use of evidence from public statements, websites, distributor pages, and operational records. It supports a specific case study, not a claim that every investigational device has identical study, access, or labeling requirements. Significant-risk studies, nonsignificant-risk investigations, exempt investigations, and expanded-access situations require their own Part 812 assessment [11].

1. Channel 1 — Hospital Compassionate/Emergency-Use Shipments (21 CFR § 812.35(a)(1)) and Internal Work Instructions Invoking the Inapplicable Federal "Right to Try Act" (WI017 and WI-00011): Under 21 CFR § 812.35(a)(1), a sponsor must obtain FDA approval prior to implementing a change to an investigational plan except for certain changes described in 21 CFR § 812.35(a)(2) through (a)(4) (such as emergency use deviations required to protect the life or physical well-being of a subject in an emergency, which must be reported to FDA within 5 working days after learning of the use under § 812.35(a)(2)) [6] [11]. CDRH found that no exception applied to ExThera's circumstances: - According to ExThera's "Emergency/Compassionate Use Requests" log and emails dated April 27–28, 2024, ExThera shipped Seraph 100 devices to a hospital ((b)(4), (b)(6) Hospital) on April 29, 2024 for treatment of a patient under the Compassionate Use (CU) pathway without obtaining prior FDA approval, and failed to follow its own work instruction WI017, "Use of Unapproved Devices in United States," which required submitting an IDE supplement under § 812.35(a) prior to compassionate use [6]. - A second Emergency/CU request for the same hospital was received on November 5, 2024, where the log noted "devices on hand" and emails dated November 5–6, 2024 indicated the devices were approved for emergency use, yet no report was ever submitted to FDA documenting the distribution of the devices for treating the identified patient [6]. - In its written response dated June 25, 2025, ExThera stated that in both the April and November 2024 cases, the devices shipped for compassionate use were not used due to changes in the patient's circumstances; however, CDRH noted that ExThera failed to indicate whether those unused devices were returned or properly disposed of, creating device-accountability risks [6]. - Furthermore, ExThera initiated an updated work instruction WI-00011 (piloted as an update from WI017), titled "Use of Unapproved Devices in United States," which incorrectly suggested that the Seraph 100 could be distributed and used in certain states based on compliance with Federal and state "Right to Try" laws and included template letters for physicians citing use "in accordance with the Federal Right to Try Act of 2017, 21 U.S.C. §§ 360bbb-0a through 360bbb-0c" [6]. CDRH ruled that the Federal Trickett Wendler, Frank Mongiello, Jordan McLinn, and Matthew Bellina Right to Try Act of 2017 is not applicable to medical devices (applying exclusively to eligible investigational drugs and biologics under 21 U.S.C. § 360bbb-0a, as verified in Source #s12), and that compliance with a conflicting state Right to Try law does not relieve a device sponsor of compliance with Federal law [6] [12]. (Separately, under BIMO Citation 2, CDRH cited 21 CFR §§ 812.40 and 812.46(a) because ExThera failed to ensure proper monitoring of the Purify and Oscar studies and signed an affidavit on June 4, 2025 confirming that when requested on May 30, 2025, it was unable to provide evidence of informed-consent verification required by its Clinical Monitoring Plan v2.0 and procedure CP018 [6].)
2. Channel 2 — Executive Statements on a Public Spotify Podcast (December 2024, Cited by Exact Timestamps 56:48 and 1:07:38): To establish unapproved intended uses (FD&C Act §§ 501(f)(1)(B), 502(o)) and false/misleading promotional claims (FD&C Act § 502(a), 21 CFR §§ 812.5(b), 812.7), CDRH quoted public statements by ExThera's Chief Medical Officer, Lakhmir "Mink" Chawla, M.D., on a December 2024 Spotify podcast titled "Dr. Mink Chawla: Blood Filter Seraph-100 Shows Promise To End Long COVID" [6]: - At timestamp 56:48, Dr. Chawla stated regarding long COVID: "Look we have had people under an IRB… under compassionate use with long COVID get the filter… clinically, their brain fog has improved, their fatigue has improved, and so clinically we're seeing real benefit" [6]. - At timestamp 1:07:38, Dr. Chawla stated: "This device has been in over 2,500 patients now, it's very safe. It's as safe as a dialysis procedure. So when you have a nice safety profile, you can move from the sickest patients in the intensive care unit which is what we did for COVID, and now we're moving into outpatients who have cancer, who have long COVID, chronic viremia, chronic Lyme, etc. … and can we help people to treat the disease of aging" [6].
3. Channel 3 — Hosted Conference and Promotional Videos (Vimeo, September and November 2024): CDRH cited two public Vimeo recordings featuring Dr. Chawla [6]: - A September 2024 presentation at an Abundance360 Longevity Platinum conference in San Diego (vimeo.com/1014979373, captioned "This video introduces the ExThera Filter which Lumati is offering as part of its unique HemoDetox protocol"), in which Dr. Chawla stated that the device is safe, effective at removing a broad range of pathogens, effective for COVID treatment, and "... approved in the US for COVID-19," while an EUA, when in force, was not FDA approval and did not authorize all promoted uses [6]; and - A November 2024 promotional video for HemoDetox treatments (vimeo.com/1031732539), in which Dr. Chawla stated that the device is effective at removing pathogens and has shown clinical benefit in treating long COVID [6].
4. Channel 4 — Foreign Distributor Web Pages (Quadrant Clinical Care) and FDA's July 17, 2024 IHCTOA Letter: CDRH documented that on July 17, 2024, FDA had issued an It Has Come to Our Attention (IHCTOA) Letter to ExThera notifying the firm that a foreign distributor, Quadrant Clinical Care (Quadrant), was promoting the Seraph 100 device on its public webpage and falsely stating that the device was FDA cleared to treat COVID-19 and sepsis [6]. In that IHCTOA letter, FDA notified ExThera that as the U.S. device manufacturer, ExThera should ensure that distributors outside the United States do not falsely claim that the device has FDA clearance or approval [6]. Although ExThera's July 25, 2024 response to the IHCTOA letter acknowledged that the Seraph device "is not currently approved or cleared by FDA for any indication" and affirmed its commitment to ensuring that distributor marketing materials accurately describe the product's U.S. regulatory status (and FDA had similarly requested removal of promotional safety/effectiveness claims during interactive review of IDE supplement G230144/S002 on July 26, 2024), CDRH found that ExThera's subsequent public statements and website content were inconsistent with those commitments [6].
5. Channel 5 — Corporate Website FAQ Page (extheramedical.com, Observed May 29, 2025): During the inspection on May 29, 2025, investigators observed that https://extheramedical.com included a Frequently Asked Questions (FAQ) section titled "Are there any known side effects or potential dangers?" stating: "The Seraph 100 safety profile is consistent with standard extracorporeal labeling" [6]. CDRH explained that because Seraph 100 is not approved for marketing in the United States, a determination of safety or effectiveness has not been completed and its risks are undetermined for U.S. patients; the FAQ statement misleadingly implied that the device's safety profile had been established as consistent with approved extracorporeal devices [6]. Although ExThera revised the webpage after the inspection, CDRH deemed the response inadequate because ExThera's corrective actions still lacked a plan to communicate with its distributors to ensure distributor promotional materials do not represent the investigational device as safe and effective or approved [6].

5.3 Deep-Dive Case Study 2: Diasol, Inc. (MARCS-CMS 719460, January 29, 2026) — Inspectional-Record and Product-Label Intended-Use Enforcement Without Website Quotes

To avoid the analytical error of assuming that 21 CFR § 801.4 and 21 CFR § 807.81(a)(3)(ii) intended-use enforcement occurs only when a company publishes website copy, podcasts, or videos, compare ExThera with Warning Letter MARCS-CMS 719460, issued by CDRH eight days earlier on January 29, 2026 (posted March 3, 2026, addressed to Owner and President Monica F. Abeles) following an FDA inspection of Diasol, Inc.'s facility in Phoenix, Arizona from July 21, 2025, through August 19, 2025 [7].

During the Phoenix inspection, FDA investigators determined that Diasol manufactures dialysate concentrates and disinfectants used in hemodialysis (Diasol Bicarb, Diasol Concentrate, Diasol Additives, and CitriSol Concentrate) and cited an Unapproved Device Violation (FD&C Act §§ 501(f)(1)(B), 502(o)) for Diasol's solutions of Citric Acid in 50% and 20% concentrations indicated for use in the cleaning, decalcification, and heat disinfection of hemodialysis machines [7].

In the pivotal paragraph of the Unapproved Device Violation section, CDRH wrote:

"While you do have a clearance under section 510(k), K020231, for a Citric Acid product intended for use with sorbent regenerated dialysis to allow physicians to customize the dialysate to meet patients' needs, that product is not intended for use in the disinfection of hemodialysis machines. Accordingly, you were required to submit a premarket notification (510(k)) for your solutions of Citric Acid in 50% and 20% concentrations indicated for use in the cleaning, decalcification, and heat disinfection of hemodialysis machines (see 21 CFR 807.81(a)(3)(ii))." [7]

In addition to the unapproved 50% and 20% Citric Acid machine-disinfection indication, the Diasol warning letter cited 13 Quality System Regulation (21 CFR Part 820) violations—including Observation 9A (21 CFR § 820.30(j)), which noted that Diasol lacked a Design History File for its 50% and 20% Citric Acid solutions used for cleaning, decalcification, and disinfecting hemodialysis machines despite manufacturing and distributing batches since 2022 (for which Diasol stated it suspended sales as of September 1, 2025 while determining whether a 510(k) was needed)—alongside Medical Device Reporting (21 CFR Part 803) violations for its 21 CFR § 876.5820 (Product Code KPO) dialysate concentrate and Unique Device Identification / GUDID (21 CFR Parts 801/830) labeling violations [7] [13] [14]. Crucially, the Diasol warning letter contains zero website quotes, podcast citations, or social media references; physical product labeling and facility inspectional records alone established that repurposing a K020231 citric acid product cleared for sorbent regenerated dialysate customization into a 50% and 20% hemodialysis machine cleaning, decalcification, and heat-disinfection product violated 21 CFR § 807.81(a)(3)(ii) [7] [10].

Taken together, the WHOOP (July 14, 2025 / June 17, 2026), ExThera (February 6, 2026), and Diasol (January 29, 2026) letters demonstrate that 21 CFR § 801.4 and 21 CFR § 807.81(a)(3)(ii) operate across every surface where a firm defines what its product is intended to do:

• In WHOOP, website claims ("delivering medical-grade health & performance insights"), an associated sleep article, and an in-app green/yellow/orange target-range gauge caused a wrist-worn PPG feature to be cited as an unapproved Class II blood pressure measurement device (21 CFR § 870.1130, DXN), until product and labeling modifications aligned BPI with the January 6, 2026 General Wellness guidance [1] [4] [5];
• In ExThera, CMO statements on a December 2024 Spotify podcast (56:48 and 1:07:38) and September/November 2024 Vimeo videos, foreign distributor web pages (Quadrant Clinical Care, cited in FDA's July 17, 2024 IHCTOA letter), a May 29, 2025 website FAQ safety claim, unapproved/unreported April and November 2024 hospital compassionate/emergency-use shipments, and updated work instruction WI-00011 invoking the inapplicable Federal Right to Try Act established both Part 812 BIMO violations and unapproved-device/misbranding violations [6] [11] [12]; and
• In Diasol, marketing 50% and 20% Citric Acid solutions for cleaning, decalcification, and heat disinfection of hemodialysis machines when existing clearance K020231 covered only citric acid for customizing dialysate in sorbent regenerated dialysis triggered 21 CFR § 807.81(a)(3)(ii) enforcement from facility inspectional and labeling records alone [7] [10].

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6. Operational Content, UI, and Validation Governance Matrix for Digital Health, SaMD, and MedTech Teams

Marketing, product management, medical affairs, and regulatory teams frequently operate in disconnected silos: engineering ships an in-app color gauge or push notification during a sprint; content writers publish an SEO blog post linking a wearable sensor to hypertension or sleep apnea; an executive speaks on an external podcast; or a distributor translates a product sheet for an international clinic. Under 21 CFR § 801.4, CDRH evaluates all of those artifacts as a single evidentiary record [4] [6] [8].

The following matrix is an author-proposed communications control, not an exhaustive classification scheme or a new FDA requirement. Binding statutes and regulations are cited as legal requirements; guidance describes FDA's policies and recommendations; suggested inventories, interface labels, contracts, and review gates are implementation choices. Apply the assessment to each function, not mechanically to a SKU or screen. A single interface may contain several functions with different statuses, and exempt devices must not be described as cleared. PMA, De Novo, and other routes also exist beyond the scenarios shown [1] [2] [10] [11].

Table 5. Suggested communications checks for selected regulatory scenarios

6.1 Actionable Pre-Publication Audit Workflow for MedTech and Digital Health Teams

To operationalize Table 5 across website updates, app store releases, content marketing, and executive communications, regulatory and marketing leaders can implement a four-step governance protocol (distinguishing binding statutory/regulatory mandates and FDA guidance criteria from practical engineering and contractual implementation measures):

Start with a function inventory. Record the intended user, population, inputs, outputs, claims, deployment context, and asserted regulatory basis for each function. Map multiple functions on a screen separately; do not assign one status to an entire SKU merely for presentation convenience. Company A–D examples in this article are hypothetical composites, not anonymized client case studies. The inventory is a practical control that helps website, app, sales, and scientific teams refer to the same scope.

Check the claim against the actual authorization or policy. For a cleared device, use that device's own authorized scope rather than a predicate's characteristics. Assess whether a change could significantly affect safety or effectiveness or involves a major intended-use change under 807.81(a)(3), accounting for an applicable authorized predetermined change control plan where relevant. A change in architecture does not by itself prove that a new 510(k) is required; a documented assessment is needed. For an exempt device, verify exemption limits separately from other regulatory requirements [10] [22].

Connect evidence to the interface. A “Basis for Recommendation” view is one implementation option for explaining inputs, logic, supporting evidence, limitations, and known unknowns to an HCP. It does not by itself establish that the statutory criteria are satisfied. For a wellness feature, examine both the literal text and how visual ranges, alerts, and contextual language shape intended use. A disclaimer cannot necessarily neutralize contradictory functionality or clinical promotion. Release notes and a versioned claim library can help keep public descriptions aligned with the assessed product [1] [2] [8].

Treat study communications as their own context. Recruitment materials generally require the applicable IRB review, while a basic clinical-trial listing containing only limited identifying and contact information may fall within FDA's stated exception. Do not generalize that exception to persuasive recruitment advertising. Part 812 labeling obligations should be applied to the investigational device and context; the regulation does not establish a universal requirement that every UI screen display the caution statement. Significant-risk studies, nonsignificant-risk studies under abbreviated requirements, exempt investigations, and expanded access should not be collapsed into one “FDA-approved protocol” category [11] [23].

Coordinate the channels that can change the message. Spokesperson preparation, distributor agreements, website audits, and alignment of quality documentation are recommended organizational controls. The ExThera and Diasol letters show why those records can matter; they do not prescribe one universal communications software architecture. When a correction is needed, track the affected claim, the channels carrying it, the owner, and the effective version, rather than changing only a landing-page headline while leaving contradictory sales material in circulation [6] [7].

For a team planning a new website, LinkedIn program, PR campaign, or evidence-led content library, VayoMed can help organize this claim-to-source mapping and maintain consistent public materials with the client's regulatory and clinical owners. A useful discovery brief includes the actual functions, authorization records, target audiences, launch markets, and existing claims. Content work supports that governance process; it does not guarantee a regulatory classification, clearance, or enforcement outcome.

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7. Methodological Limitations and Scope Constraints

To preserve analytical precision and avoid over-interpreting public regulatory datasets, five methodological limitations govern the findings in this report:

1. openFDA Linked Identifier Array Lengths vs. Active Market Volume: In the preserved openFDA classification dataset (snapshot 2026-09-21, 7,093 product codes), the openfda.k_number and openfda.registration_number fields are arrays of linked K-number identifiers and linked facility registration identifiers attached to each product_code during openFDA data harmonization [14] [15]. Those array lengths (Table 2) measure identifier linkage density across product codes; they do not represent complete historical 510(k) clearance totals, active commercial device listing counts, or unit sales volume.
2. Raw submission_type_id Codes Beyond deviceclass_reference.pdf: While FDA's official Device Classification Reference (deviceclass_reference.pdf) defines device_class (1, 2, 3, U, N, F/f=HDE) and submission_type_id values 1 (510(K)), 2 (PMA), 3 (Contact ODE), and 4 (510(K) Exempt), the 2026-09-21 openFDA JSON payload also contains raw submission_type_id codes 6 (n = 57), 7 (n = 306), 8 (n = 42), and blank "" (n = 214) [14] [15]. The inspected field dictionary does not define every raw code found in the export. This report therefore reports raw codes 6, 7, 8, and "" directly and examines the embedded definitions of focal submission_type_id=7 codes (OCH, PGJ, PEV, PPH, PPI, PPL, PRO) alongside FDA guidance, rather than treating a raw code as an independent legal status determination [1] [3] [14] [15].
3. Warning Letter Corpus Cutoff Dates and Issuing-Office Subset Boundaries: The preserved source record dataset (20260731_full extract, archived snapshot 2026-08-16, 3,643 indexed letters) contains letter_issue_date values through 2026-07-23 (posted_date through 2026-07-28), and within the issuing_office == "Center for Devices and Radiological Health" subset (n = 220 across 2021–2026; n = 82 across 2025–2026), letter_issue_date runs through 2026-06-15 (posted_date through 2026-07-22) [16]. Matching that exact issuing_office string captures only letters issued directly under the CDRH office name and does not capture device-related letters issued by the Office of Inspections and Investigations or import divisions [16].
4. Descriptive Snapshot Close-Out Counts Subject to Right-Truncation: The close-out letter counts and percentages in Table 3 (26.36% overall across 2021–2026 CDRH letters; 47.37% for 2021 vs. 21.31% for 2025 and 0.00% for 2026 through 2026-06-15) reflect point-in-time snapshot records with unequal follow-up duration across issue years [16]. They must not be interpreted as final longitudinal resolution rates or causal estimates of enforcement stringency.
5. No Inferred Prevalence of Website Quotations Across Unread Warning Letters: While the full texts of the WHOOP (July 14, 2025 / June 17, 2026), ExThera (February 6, 2026), and Diasol (January 29, 2026) letters were inspected from official FDA HTML/text records [4] [5] [6] [7], the 3,643-record metadata index records issuing office, subject, issue/posted dates, and close-out dates rather than full letter bodies [16]. Accordingly, this report does not claim a corpus-wide percentage of warning letters quoting websites or podcasts, and explicitly pairs ExThera and WHOOP (multi-channel digital/UI evidence) with Diasol (physical labeling and inspectional records without website quotes) to illustrate both enforcement patterns.

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Sources

1. U.S. Food and Drug Administration, Center for Devices and Radiological Health (CDRH). General Wellness: Policy for Low Risk Devices — Guidance for Industry and Food and Drug Administration Staff (Document Number 1300013, issued January 6, 2026, superseding the September 27, 2019 guidance). Verified from full official PDF (the preserved source record, 11 pages): https://www.fda.gov/media/90652/download (Guidance landing page: https://www.fda.gov/regulatory-information/search-fda-guidance-documents/general-wellness-policy-low-risk-devices).

2. U.S. Food and Drug Administration (CDRH, CDER, CBER). Clinical Decision Support Software — Guidance for Industry and Food and Drug Administration Staff (Document Number GUI01400062, issued January 29, 2026, superseding the January 6, 2026 guidance). Verified from full official PDF (the preserved source record, 27 pages): https://www.fda.gov/media/109618/download (Guidance landing page: https://www.fda.gov/regulatory-information/search-fda-guidance-documents/clinical-decision-support-software).

3. U.S. Food and Drug Administration (CDRH, CBER). Policy for Device Software Functions and Mobile Medical Applications — Guidance for Industry and Food and Drug Administration Staff (Document Number 1741, issued September 28, 2022, with February 2, 2024 Quality Management System Regulation cover note). Verified from full official PDF (the preserved source record, 41 pages): https://www.fda.gov/media/80958/download (Guidance landing page: https://www.fda.gov/regulatory-information/search-fda-guidance-documents/policy-device-software-functions-and-mobile-medical-applications).

4. U.S. Food and Drug Administration, Center for Devices and Radiological Health. Warning Letter to WHOOP, Inc. (MARCS-CMS 709755, issued July 14, 2025, posted July 15, 2025). Verified from full official letter text (the preserved source record): https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/whoop-inc-709755-07142025.

5. FDA. WHOOP, Inc., Close-Out Letter, MARCS-CMS 709755. June 17, 2026. Official letter.

6. U.S. Food and Drug Administration, Center for Devices and Radiological Health. Warning Letter to ExThera Medical Corporation (MARCS-CMS 715068, issued February 6, 2026, posted February 24, 2026). Verified from full official letter text (the preserved source record): https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/exthera-medical-corporation-715068-02062026.

7. U.S. Food and Drug Administration, Center for Devices and Radiological Health. Warning Letter to Diasol, Inc. (MARCS-CMS 719460, issued January 29, 2026, posted March 3, 2026). Verified from full official letter text (the preserved source record): https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/diasol-inc-719460-01292026.

8. U.S. National Archives and Records Administration, Electronic Code of Federal Regulations (eCFR). Title 21, Chapter I, Subchapter H, Part 801, Subpart A — General Labeling Provisions, 21 CFR § 801.4 (Meaning of intended uses) (current as of October 22, 2026; verified from the preserved source record): https://www.ecfr.gov/current/title-21/chapter-I/subchapter-H/part-801/subpart-A/section-801.4.

9. U.S. Food and Drug Administration. Final Rule: Regulations Regarding "Intended Uses" (86 FR 41383, Document 2021-15980, Docket No. FDA-2015-N-2002, published August 2, 2021, effective September 1, 2021, amending 21 CFR §§ 201.128 and 801.4; verified from the preserved source record): https://www.federalregister.gov/documents/2021/08/02/2021-15980/regulations-regarding-intended-uses.

10. U.S. National Archives and Records Administration, Electronic Code of Federal Regulations (eCFR). Title 21, Chapter I, Subchapter H, Part 807, Subpart E — Premarket Notification Procedures (21 CFR §§ 807.81–807.100, including § 807.81(a)(3) and § 807.97) (retrieved October 15, 2026, reflecting latest codified amendment at 89 FR 18792–18793, March 15, 2024; verified from the preserved source record): https://www.ecfr.gov/current/title-21/chapter-I/subchapter-H/part-807.

11. U.S. National Archives and Records Administration, Electronic Code of Federal Regulations (eCFR). Title 21, Chapter I, Subchapter H, Part 812 — Investigational Device Exemptions (21 CFR §§ 812.1–812.47, including § 812.5 Labeling, § 812.7 Prohibition of promotion, § 812.20 Application, § 812.35 Supplemental applications, § 812.36 Treatment use, and § 812.46 Monitoring) (current as of October 22, 2026; verified from the preserved source record, ecfr_812_b.txt, and ecfr_812_c.txt): https://www.ecfr.gov/current/title-21/chapter-I/subchapter-H/part-812.

12. U.S. Food and Drug Administration. Right to Try (Trickett Wendler, Frank Mongiello, Jordan McLinn, and Matthew Bellina Right to Try Act of 2017, Pub. L. 115-176, 21 U.S.C. § 360bbb-0a; content current as of December 12, 2024, verified October 24, 2026 from the preserved source record): https://www.fda.gov/patients/learn-about-expanded-access-and-other-treatment-options/right-try.

13. Electronic Code of Federal Regulations. 21 CFR Medical Device Classification Regulations. Part 870, Part 876, Part 878, Part 862, and Part 892.

14. U.S. Food and Drug Administration. openFDA Device Classification Bulk Dataset (device-classification-0001-of-0001.json.zip, 7,093 product classification records; archived snapshot 2026-09-21, openFDA last_updated=2026-09-14, SHA-256: 5740b45d0b3d35f6182d5e663b2b1485496323c406122a7eba3790e61a379903, analyzed via the preserved source record): https://download.open.fda.gov/device/classification/device-classification-0001-of-0001.json.zip.

15. U.S. Food and Drug Administration, openFDA. Device Classification Reference (deviceclass_reference.pdf, official field dictionary for device_class, submission_type_id, unclassified_reason, gmp_exempt_flag, third_party_flag, and openfda identifier arrays; verified from the preserved source record): https://open.fda.gov/fields/deviceclass_reference.pdf.

16. U.S. Food and Drug Administration. FDA Warning Letters Corpus (the preserved source record, 20260731_full extract, warning_letters_all.jsonl, 3,643 indexed warning letters with all-FDA letter_issue_date through 2026-07-23 and CDRH-office subset letter_issue_date through 2026-06-15; archived snapshot 2026-08-16, SHA-256: 8b33857bb2f56f6fb0377d48ade5d6f7d0897790a04b5fd98c625c6684abdbeb, analyzed via the preserved source record): https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/compliance-actions-and-activities/warning-letters.

17. United States Code. 21 USC 360j(o), software functions. Source.

18. FDA. Do Not Use Smartwatches or Smart Rings to Measure Blood Glucose Levels: FDA Safety Communication. February 21, 2024. Source.

19. FDA. Multiple Function Device Products: Policy and Considerations. July 29, 2020. Source.

20. FDA. ExThera Seraph 100 emergency use authorization. April 17, 2020; subsequently revoked. Source.

21. FDA. Seraph 100 EUA revocation letter. November 24, 2025. Source.

22. FDA. Deciding When to Submit a 510(k) for a Change to an Existing Device. October 25, 2017. Source.

23. FDA. Recruiting Study Subjects: Information Sheet. Source.