What the 2022 Study Actually Found

A clinical validation study published in Frontiers in Cardiovascular Medicine tested the Samsung Galaxy Watch Active 2 against 24-hour ambulatory blood pressure monitoring — the real clinical gold standard — in both normotensive and hypertensive patients. The finding was specific and genuinely concerning: smartwatch blood pressure accuracy showed a systematic bias toward the calibration point, meaning low readings got pushed higher and high readings got pushed lower than they actually were.

In practical terms: sensitivity for detecting hypertension was 83%, but specificity was only 41% — meaning the device correctly flagged genuinely high blood pressure a majority of the time, but also frequently gave false reassurance. The study’s own conclusion was direct: smartwatch-based BP measurement was “not yet ready for clinical usage.”

The Evidence Has Genuinely Changed

This is worth stating honestly, since most content treats “smartwatches are inaccurate” as a fixed, permanent verdict. It isn’t.

A newer study, published in January 2026 and using the more recent Samsung Galaxy Watch 5, followed 37 participants through a 28-day protocol of paired measurements against a validated reference sphygmomanometer. The result was meaningfully different: the smartwatch met accuracy criteria based on ISO and IEEE standards in all but one measure. This is a genuine, documented improvement over four years — not a marketing claim, an actual peer-reviewed finding.

The American Heart Association weighed in too, and its language was notably blunt for a professional body. A scientific statement published online in December 2025, formally appearing in the journal Hypertension in 2026 and chaired by Dr. Jordana Cohen of the University of Pennsylvania, made a specific, important distinction most consumers never hear: FDA clearance does not mean a cuffless device has undergone the kind of clinical validation needed to establish real-world accuracy. A formal validation protocol isn’t actually required to get FDA clearance in the first place — many devices are tested against far less rigorous standards than people assume when they see a “cleared” label on a box.

The Wider Device Landscape You Haven’t Heard About

Apple and Samsung dominate the conversation, but the field has genuinely expanded. Oura, Whoop, and a growing set of finger-worn rings now market some form of blood pressure tracking, and it’s worth knowing how they differ before assuming they all work the same way.

Notice the pattern: apart from Omron’s genuine inflatable cuff, every other device on this list — including Samsung’s — estimates pressure optically and leans on periodic real-cuff calibration to stay accurate. None of them measure pressure directly the way a doctor’s office does. If accuracy and clinical decision-making are genuinely the priority, an upper-arm cuff (or Omron’s cuffed watch specifically) remains the more medically defensible default, not a cuffless optical device, however recent its release date.

Why This Actually Matters

High blood pressure isn’t a minor inconvenience being tracked out of curiosity — it’s a leading contributor to roughly 9.4 million deaths worldwide each year, and it’s genuinely the kind of condition that stays silent until a stroke or heart attack makes it visible. This is exactly why the appeal of continuous, wrist-based monitoring is real, and why getting the accuracy question right actually matters, rather than being a minor technical footnote. A separate 2025 Northumbria University validation study, evaluating the Huawei D2 watch against combined AAMI, ESH, and ISO international standards, reflects just how much clinical attention this exact technology category is now receiving — it’s a genuinely active, fast-moving area of medical device research, not a settled question either direction.

Samsung vs Apple: Two Different Approaches

These two major brands solve this problem in genuinely different ways, and confusing them leads to real misunderstanding about what your specific device can and can’t tell you.

Apple’s hypertension notification feature, FDA-cleared in September 2025 and launched in India, works entirely differently — it uses the optical heart sensor to analyze how blood vessels respond to each heartbeat over a full 30-day window, and simply alerts you if a consistent hypertension pattern emerges. It never gives you a number at all. The underlying algorithm was trained using machine learning on data from over 100,000 participants across multiple studies, then specifically tested in a roughly 2,000-participant clinical trial before FDA clearance — a genuinely substantial validation effort for a feature that still, by design, stops short of giving an actual reading. Apple itself estimates this feature could help identify a million previously undiagnosed hypertension cases within a year — a genuinely significant public health contribution, precisely because it’s designed as an early-warning trend detector, not a replacement for actual measurement. Our normal blood pressure by age guide is worth reading alongside this one, since knowing your actual target range matters more than any single device’s reading.

How These Devices Actually Work

Neither approach uses a true cuff mechanism. Both rely on photoplethysmography (PPG) — optical sensors using light to detect blood volume changes with each heartbeat — combined with algorithms that estimate blood pressure indirectly from that signal pattern, rather than measuring pressure directly the way an inflatable cuff does. This is precisely why calibration against a real cuff matters so much for devices like Samsung’s: the algorithm needs a genuine reference point to translate optical signal patterns into an actual pressure estimate.

Why Calibration Is the Hidden Catch

This is the single most important, most overlooked detail in the entire smartwatch blood pressure accuracy conversation: no current wearable provides truly independent, cuffless, continuously-accurate blood pressure monitoring. Samsung’s device requires an actual arm cuff for calibration every 28 days; between those calibrations, accuracy genuinely depends on how much your physiology has changed since the last reference reading. Skip the recalibration, and accuracy drifts — a genuine, documented limitation, not user error.

Our Complete Guide to Blood Pressure covers proper cuff-based measurement technique in full, which remains the actual gold standard these wearables are still working to approximate, not replace.

Wrist Position Matters More Than Most People Realize

Even leaving the underlying technology aside, physical positioning genuinely affects every wrist-based reading. Consumer Reports’ own test engineers note that wrist devices must be correctly placed directly over the radial artery and held precisely at heart level during measurement, with minimal wrist movement — get the angle or height wrong, and the reading shifts meaningfully regardless of how good the sensor itself is.

Here’s a genuinely surprising finding worth knowing: the Omron HeartGuide, a wrist-worn device with an actual inflatable cuff built in — not optical estimation, a real mechanical cuff — was rated the lowest-scoring blood pressure monitor Consumer Reports tested, despite carrying the highest price tag of any model in their review at roughly $499. Even genuine cuff technology struggles once you move it from the upper arm to the wrist, since wrist anatomy and positioning consistency are simply harder to standardize than an upper-arm cuff at a fixed, predictable height.

The Technology Behind the Numbers

Cuffless blood pressure estimation isn’t actually new — it traces back to 1993, when Casio released the BP-100, a wristwatch combining a PPG optical sensor with an ECG sensor. Modern devices build on the same underlying family of approaches, typically falling into one of a few technical categories worth knowing by name if you want to understand what your specific device claims to do:

• PAT (Pulse Arrival Time) — measures the delay between a heartbeat (via ECG) and the pulse arriving at the wrist (via PPG); shorter delay generally correlates with higher pressure.
• PTT (Pulse Transit Time) — a related approach measuring how long a pulse wave takes to travel between two points on the body, using two separate optical sensors.
• Bioimpedance — some newer prototype designs pass a small electrical current through wrist tissue and infer pressure-related changes from the resulting signal.

None of these methods measure pressure directly the way an inflating cuff physically does — they’re all indirect estimations requiring an initial reference point, which circles back to exactly why calibration against a real cuff remains unavoidable for the foreseeable future.

What’s Coming Next: The Newest FDA Milestone

This is worth knowing about specifically because it’s the most significant recent development in this exact space. In July 2025, Swiss medtech company Aktiia received the first-ever FDA clearance for an over-the-counter, fully cuffless blood pressure monitor — the Hilo Band (officially the G0 Blood Pressure Monitoring System). Unlike Samsung’s approach, which still requires periodic cuff recalibration to continue functioning, and unlike Apple’s approach, which never gives a number at all, Hilo’s device is designed to provide continuous, ongoing readings across a full 24-hour cycle after an initial one-time calibration.

The device already carries a CE mark and has over 130,000 users in Europe; its FDA clearance was supported by clinical validation against reference standards including double-auscultation measurement in 140 patients. A U.S. consumer launch is expected sometime in 2026. It’s a genuinely significant regulatory milestone — the first time the FDA has authorized any cuffless BP device for OTC use without requiring a prescription — though it’s also worth noting realistically that even this newest, most validated device still requires an initial cuff-based calibration to begin working, reinforcing just how central that step remains across every approach on the market right now.

The Broader Cardiovascular Picture Worth Tracking

Blood pressure monitoring rarely exists in isolation from the rest of your cardiovascular health. If you’re already managing risk factors, our heart attack in young adults guide and anger and blood pressure guide are both worth reading alongside this one. If cholesterol management is part of your routine, our statins guide is relevant too, since these conditions are frequently monitored together. Chronic stress genuinely affects both the accuracy of a single reading and your actual baseline — our mental stress guide covers this overlap. If you’re managing diabetes alongside blood pressure, our diabetes medicine safety guide and diabetic foot care guide both cover genuinely overlapping territory. The free Blood Report Decoder and Biological Longevity Audit are both worth using for a broader sense of where things stand.

An Interesting Side Effect: Checking Too Often Can Backfire

Here’s a genuinely underdiscussed angle worth mentioning directly: constant, anxious re-checking of a smartwatch BP feature can itself raise your reading. This isn’t a data quirk — it’s a real physiological response. The anticipatory stress of repeatedly checking a number you’re worried about triggers its own acute rise in blood pressure, similar in mechanism to the white-coat effect covered in our fluctuating blood pressure guide. Someone who checks a wrist-worn BP feature every few minutes, hunting for reassurance, can genuinely create a self-reinforcing loop where the checking behavior itself becomes a measurable stressor. A sensible middle ground — checking on a set schedule rather than compulsively, and treating any single alarming number as a prompt to breathe and recheck later rather than react immediately — tends to produce both calmer users and more representative readings.

How to Use a Smartwatch BP Feature Well

Given everything covered above, a smartwatch BP feature is still genuinely worth using — just with realistic expectations about what it can and can’t tell you. Our morning blood pressure spikes guide is worth reading alongside this one, since the time of day you happen to check your watch genuinely affects what number you’ll see, independent of any device accuracy question entirely.

• Calibrate on schedule — don’t skip the periodic cuff-based recalibration if your device requires it.
• Treat readings as trend data, not diagnostic numbers — a pattern over weeks tells you more than any single reading.
• Confirm any alert with a real cuff — exactly as Apple’s own guidance recommends: log with an actual cuff for 7 days before assuming a trend alert reflects true hypertension.
• Measure consistently — same arm, seated, rested, similar to proper cuff technique, for whatever comparison value the smartwatch data still offers.

When to Trust an Actual Cuff Instead

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