Apple vs WHOOP: Two Blood Pressure Strategies, Two Very Different Regulatory Journeys

Two wearables. One vital sign. Two radically different interpretations of what counts as a medical device.

As Apple moves forward with FDA-cleared blood pressure monitoring, WHOOP finds itself on the defensive — arguing that its feature is a “wellness insight” exempt from regulation. Both companies use wrist-based sensors. Both want to shape the future of preventive health. But their regulatory stories couldn’t be more different.

Here we’re not just talking about approvals and warning letters. It’s a case study in how intent, design, and evidence define the boundaries between innovation and oversight.

WHOOP’s Warning Letter: When Wellness Meets the FDCA

In July 2025, WHOOP received an FDA Warning Letter over its Blood
Pressure Insights feature, which estimated systolic and diastolic values using sleep-based sensor data and machine learning.

While labelled “not for clinical use,” the app presented mmHg values, color-coded abnormal ranges, and bundled the tool within a suite of “medical-grade insights.” FDA concluded that these elements positioned the feature as a regulated medical function.

Under 21 CFR §801.4 and Section 201(h) of the FDCA, FDA made its position clear: disclaimers don’t override design or user perception. Once a product displays diagnostic thresholds — like 140/90 mmHg — it enters the territory of disease diagnosis and therefore regulation.

WHOOP’s official response was cautious, noting the feature was disabled in the U.S. and that the company was “engaging with the FDA to better understand and resolve their concerns.” CEO Will Ahmed has argued more forcefully, citing the 21st Century Cures Act, which exempts certain “general wellness” products from premarket review.

But FDA’s counterpoint is equally forceful: heart rate or step count may be wellness features, but blood pressure is directly tied to disease thresholds. That difference puts it under the medical device framework.

At present there’s no recall, no Form 483, and no allegations of harm. But the BP feature remains deactivated in the U.S.

Apple’s Quiet, Clinical Pathway

In contrast, Apple has now secured FDA clearance to launch a hypertension notification feature for its smartwatch line, as confirmed by Reuters on September 13, 2025. The tool will be available on Apple Watch Series 9, 10, 11, and the Ultra 2/3 models, and will roll out in over 150 countries including the US and EU. Details remain limited, but early reports suggest:

• Passive 30-day data analysis.
• No real-time mmHg values shown.
• Uses optical heart sensors to detect vascular pulse responses.
• Alerts users to consistent signs of hypertension, but not every case.
• Expected to notify around 1 million users.

A third player — Hilo (the rebranded successor to Swiss company Aktiia) — offers yet another approach. Hilo recently received FDA clearance (K250415) for its PPG-based bracelet. Unlike WHOOP, Hilo presented its product from day one as a Class II medical device, not a wellness feature. Apple’s conservative, clinical-first approach avoids the “wellness vs medical” ambiguity, and shows how a diagnostics-adjacent feature can be made regulator-ready from day one.

Hilo’s Middle Path: PPG Done by the Book

Hilo’s clearance shows what “by-the-book” looks like for photoplethysmography (an optical technique that uses a light source and a photodetector to measure changes in blood volume in the microvasculature of the skin) :

• Daily calibration with a cuff.
• Spot checks only.
• Structured validation study meeting ISO 81060-2.

It was enough for FDA clearance, but some regulatory observers note gaps. The validation didn’t capture nocturnal or medication-induced BP changes, both critical in hypertension care. FDA’s public summary didn’t address these limits.

This highlights a broader regulatory blind spot: clearance often reflects minimum acceptable validation, not comprehensive real-world utility.

Lessons for Founders and Product Teams

The lesson isn’t that one company got it “right” and the other “wrong.” WHOOP’s misstep shows how even experienced teams can misjudge regulatory lines — especially with evolving technologies.

For teams building next-gen health features:

• UI matters. If your interface mimics a clinical tool, regulators may treat it as such.
• Evidence still comes out on top. Structured validation, not correlations or testimonials, remains the FDA gold standard.
• Engage early. Don’t launch features near diagnostic thresholds without alignment.
• Be intentional. Not every feature should be a medical device — but if you present blood pressure in mmHg, regulators will interpret it that way.

Think of it as a checklist: interface, evidence, regulatory intent, and market positioning. Get two wrong and you’re in trouble.

A Crossroads for Digital Health

Blood pressure is not just another ‘simple’ metric. It’s a vital sign with direct clinical consequences. The choices made by WHOOP, Apple, and Hilo will shape how both consumers and regulators view the next generation of biosensing tools.

As wearables increasingly straddle wellness and medicine, the question isn’t whether regulation applies, but how early, how clearly, and how well companies prepare for it.

Will the next breakthrough come from those who blur the line, or those who draw it clearly?

Disclaimer. The views and opinions expressed in this article are solely those of the author and do not necessarily reflect the official policy or position of Test Labs Limited. The content provided is for informational purposes only and is not intended to constitute legal or professional advice. Test Labs assumes no responsibility for any errors or omissions in the content of this article, nor for any actions taken in reliance thereon.