Can a smartwatch measure your blood pressure? What the FDA's Whoop decision actually means

Short answer

Most smartwatches don't measure your blood pressure, and the few that estimate it aren't measuring it the way a cuff does. They use the same optical sensor that reads your pulse and infer a number from the shape of the signal. That inference can track trends for one person over time; it is not a substitute for a validated upper-arm cuff, and no mainstream wrist wearable sold in the US is cleared to replace one.

Originally published on Founder And The City, Jane's newsletter about building in health tech. This version is written for the person asking whether their watch can do this, rather than for the people who build the devices.

If you've spent time hunting through your device's settings for this and come up empty — you're not imagining it, and you haven't missed anything. The feature genuinely isn't there, on almost every device, and the reason has nothing to do with you or with your particular model. Your watch almost certainly has the sensor. What's missing is permission.

In July 2025 the FDA sent Whoop a warning letter over exactly this: one daily blood pressure estimate, taken during sleep, from the optical sensor already in the band. The agency's position was that blood pressure measurement is inherently linked to diagnosing hypertension, which makes any such feature a medical device requiring full clearance. Whoop publicly disagreed, arguing the feature was wellness information — the same category as breathing rate or heart rate variability.

That distinction is worth understanding, because it shapes what you can and can't expect from consumer health tech, and because it affects whether people find out about high blood pressure early or late.

Why blood pressure is treated differently from everything else on your wrist

Look at what your wearable is already allowed to show you without any clearance at all.

Heart rate. Standard on every device. An abnormal heart rate can signal cardiac problems.

Heart rate variability. Standard. Reflects autonomic nervous system function, and is used in research on everything from overtraining to chronic illness.

Respiratory rate. Standard. Breathing patterns change in infection, heart failure and sleep-disordered breathing.

Blood oxygen. Widely available as a wellness feature. Oxygen saturation links directly to lung and cardiac disease.

Each of these is a physiological signal that can indicate serious illness. None of them triggers the medical device pathway when presented as wellness information.

Blood pressure does. The reasoning is that BP is "inherently linked" to diagnosing hypertension — so a feature showing it is, by definition, a diagnostic feature. In the Whoop letter the supporting evidence included a single sentence on the company's website noting that elevated blood pressure can be a sign of poor sleep, and the use of colour-coded zones in the interface.

Our view, and it is an opinion rather than a fact: that distinction is historical rather than clinical. Blood pressure has traditionally been measured in clinical settings, so any consumer feature touching it inherits the clinical pathway. It is not obviously riskier to show someone a blood pressure trend than to show them a blood oxygen reading.

What it actually takes to clear that pathway

This is where the practical consequence sits, and it explains why you see so few of these features.

The filing fee itself is modest — around $24,000, or roughly $6,000 for a small business. That's the visible cost, and it's not the one that matters. By Jane's estimate from running a preventive health company, getting a consumer blood pressure feature through the medical device pathway runs somewhere between half a million and one and a half million dollars, and takes twelve to twenty-four months. That's software validation, cybersecurity testing, usability studies, small clinical trials, a quality management system and regulatory consultants — before a single user sees the feature.

The money is the visible cost. The less obvious one is speed.

Consumer software ships updates weekly. Preventive health products in particular live or die on engagement: roughly nine in ten people abandon a health app within the first week, so the work is constant iteration on messaging, timing, interface and personalisation. Regulatory clearance freezes the product. You submit version one and wait. After approval, meaningful changes require resubmission.

For a product that treats diagnosed patients, that trade-off makes sense. Someone managing diabetes with a glucose monitor is not going to delete the app because the copy is clumsy — they need it. For a product aimed at healthy people who are trying to stay healthy, a two-year freeze is close to a death sentence, because by the time you launch, whatever made people stick around has gone stale. Prevention isn't competing with other medical devices; it's competing with everything else on a phone.

That matters to you as a reader more than it sounds. It's the reason the health products that survive tend to be the ones that never go near a regulated measurement — and the reason the gap between "things your watch could plausibly tell you" and "things your watch actually tells you" keeps widening in a direction nobody chose.

There's a further wrinkle: clearance doesn't guarantee anyone will pay for it. Medicare doesn't automatically cover cleared devices, and the rule that was meant to create a pathway for breakthrough devices was repealed in 2021. Commercial insurers decide separately, one at a time. So from an investor's point of view the proposition is a seven-figure spend, an eighteen-month delay, and no guaranteed market access at the end of it.

The predictable result is that very few companies attempt it, and the feature simply doesn't exist for most people.

The argument for caution — and what the numbers show

The case for the FDA's position is real and deserves stating properly: people who see a frightening number without context may panic, seek emergency care unnecessarily, and add load to a system that is already strained. That is not a silly concern, and anyone who has watched a family member spiral after one bad reading understands it.

It's worth looking at what actually happens, though. Between 2006 and 2015, somewhere in the region of 600,000 to 900,000 Americans a year went to emergency departments primarily for elevated blood pressure. Emergency medicine guidelines are explicit that asymptomatic elevated blood pressure doesn't warrant emergency treatment and should be routed to primary care for proper monitoring. Studies nonetheless find that around 80% of these patients receive diagnostic testing in the emergency department and more than 30% receive medication there. At roughly $750 a visit, the whole category costs something in the region of half a billion dollars a year.

So the over-use is real — but two things about it are worth noticing. First, it's happening in a world where consumer blood pressure features largely don't exist, so whatever is driving those visits, it isn't wearables showing people trends. Second, the professional guidance and the wearable point the same direction: both the American Heart Association and emergency physicians say an asymptomatic elevated reading should lead to home monitoring or ambulatory measurement to confirm — not to an emergency room.

Against that sits the other side of the ledger. Hypertension-related causes contributed to 664,470 deaths in the United States in 2023, and the condition carries an estimated economic burden of $219 billion a year. Set the two numbers beside each other and the ratio is roughly three hundred to one: for every dollar the health system spends on precautionary visits, it loses several hundred to hypertension found too late. Hypertension is dangerous precisely because it's silent — most people don't know they have it until something else happens.

We're not equipped to resolve that trade-off, and we're not going to pretend the answer is obvious. What we'd say is that the current line — nine physiological signals fine, the tenth forbidden — doesn't look like it was drawn by weighing those two things against each other.

There's a related oddity worth naming. The American Heart Association publishes its blood pressure categories publicly, complete with the stage thresholds everyone has seen. Anyone can look them up in ten seconds, and plenty of people already run their numbers past an AI chatbot with no oversight of any kind. What the current position rules out is a company citing those same public guidelines, with disclaimers, inside an app. The information isn't restricted. Only the accountable presentation of it is.

So what should you actually do about your blood pressure?

This is the part that matters more than the policy argument, so here it is plainly.

Use a validated upper-arm cuff. Wrist cuffs are more sensitive to position; upper-arm devices with published validation are the standard for home measurement. Your pharmacy sells them and they are not expensive.

Measure properly or don't bother. Sit with your back supported and feet flat for five minutes first. Arm supported at heart height. No caffeine, exercise or smoking in the previous half hour. Empty bladder. Don't talk during the measurement. Take two or three readings a minute apart and record all of them, not just the best one.

Measure over days, not once. A single high reading means very little. Blood pressure moves with the hour, the argument you just had, the coffee, the full bladder, the cold room. What matters is the pattern across a week or two, morning and evening. That's also exactly what a clinician will ask for.

Write it down. A simple blood pressure log is more persuasive at an appointment than any device screenshot, and it's the thing that distinguishes a real pattern from a bad morning.

Know that the clinic reading may not be your real one. White coat and masked hypertension are both common: some people read high only in the clinic, others read normal there and high everywhere else. The second is the dangerous one, and home measurement is how it gets caught.

If you're choosing a device, our guide to home blood pressure monitors covers what validation actually means and what to ignore in the marketing.

One thing worth knowing before you start: home readings are generally expected to run slightly lower than clinic readings, which is why the thresholds clinicians apply to home monitoring aren't identical to the ones printed on the pharmacy poster. If you're going to measure at home — and you should — ask which numbers your clinician wants you working to. Measuring diligently against the wrong target produces either false reassurance or unnecessary worry, and both are avoidable with one question.

It's also worth resisting the urge to average things yourself before the appointment. The pattern is the information: whether you read high in the mornings only, whether readings settle across the week, whether a particular day stands out. An average erases all of that, and it's the part a clinician can actually use. Keep the raw list.

Finally, don't chase the number between measurements. Checking six times in an evening because the first reading bothered you will reliably produce a worse second reading, because you're now anxious and sitting badly. Twice a day, at roughly the same times, is the protocol — and it exists precisely because the measurement is so easy to disturb.

When to see a doctor about blood pressure — and what to bring

Seek urgent medical help if a high reading comes with chest pain, breathlessness, weakness or numbness on one side, difficulty speaking, severe headache, vision changes, or confusion. Those are possible emergency symptoms, and the number on the screen is not the point — the symptoms are.

Book a non-urgent appointment if your home readings are consistently elevated across a week or two, if they've shifted noticeably from your usual, if you have kidney disease or diabetes, or if you're pregnant and seeing any elevation at all.

What to bring. A week of logged readings with dates, times, and all values from each sitting — not averages you calculated yourself. Note which arm, and which device. Bring the device itself if you can; clinicians will sometimes check it against theirs, which is useful either way.

What to ask for. Whether your readings justify ambulatory monitoring — a 24-hour cuff that measures while you go about your day, including overnight. It's the measurement that settles white coat and masked hypertension, and it's underused. Also ask what target applies to you specifically, since thresholds differ with age and other conditions.

If you're waved off. "I've logged fourteen readings over two weeks, taken to AHA technique, and the average is X — I'd like to understand whether that needs following up" is a hard sentence to dismiss, and it is a completely different conversation from "my watch said something weird." Ask for the reasoning to be written in your notes. That request alone tends to change the tone.

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How Welltory fits — and what it can't do

Since your watch can't give you blood pressure, it's worth being clear about what it can contribute, because it isn't nothing — and about where the line falls.

Resting heart rate over time. A resting heart rate that has drifted upward over weeks is a real signal worth noticing, and it's something we cover in detail.

Sleep and overnight recovery. Short and fragmented sleep is one of the modifiable contributors to cardiovascular risk, and unlike blood pressure it's something a wearable measures honestly.

Time spent under load. Chronic stress load is not a diagnosis, but knowing how much of your week your body actually spends in a stressed state is useful context for a conversation about blood pressure — and it's usually more than people assume.

Activity, honestly counted. Physical activity is among the most robust levers on blood pressure that exists, and most people substantially over-estimate how much of it they get.

What Welltory does not do is measure, estimate, or interpret your blood pressure. We don't have that feature, this article isn't a workaround for it, and if we did have it we'd still tell you to confirm anything that mattered with a cuff. What we can do is show you the things around it that your body is willing to report without a clinical instrument.

Where we land on the regulation

For the record, and as opinion rather than fact: we're not arguing for no oversight. Any company working in preventive health would take clear standards over the current situation in a heartbeat — defined requirements, defined timelines, defined market access. What exists now is uncertainty, large costs and no guarantee that surviving the process leads anywhere commercially.

There's also an asymmetry that's hard to ignore. Regulators have found ways to evaluate AI diagnostic systems, including ones whose internal workings nobody can fully explain, while a transparent estimate derived from an optical pulse signal sits blocked. And the precedent for doing this better already exists: when evidence showed pulse oximeters read less accurately on darker skin, the response was tighter accuracy standards, diverse testing populations and better labelling — targeted regulation aimed at a demonstrated harm, rather than a ban aimed at a hypothetical one. That is a model that would work here.

The question underneath all of this isn't really about one company's feature. It's whether people are allowed to understand their own bodies before they're sick enough to be patients.

Read more from Jane

Jane writes about products, evidence and the health industry in Founder And The City, where the original and considerably angrier version of this argument first appeared — including the full cost breakdown of the regulatory pathway, why it kills small preventive-health companies specifically, and her proposal for what a working system would look like instead.

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