Blood-pressure smartwatches: what the watch measures and what it just guesses

Wrist blood pressure is the wearable arms race of the moment. Samsung, Huawei, WHOOP, Oura, Aktiia: each promises to tell you whether you're hypertensive without that arm cuff that inflates and squeezes. The catch is that these watches don't all do the same thing. A few genuinely measure your pressure. Others look at your pulse signal and make an educated guess. And almost every regulatory fight of the past year traces back to that distinction the marketing would rather you didn't notice.

Three technologies pretending to be one

When someone says "blood-pressure smartwatch," they could mean three quite different things.

The first is oscillometric with an actual cuff. The Omron HeartGuide and Huawei Watch D2 build an air bladder (an airbag) into the strap itself, which inflates and compresses the artery at your wrist. It's the exact physical principle of the pharmacy machine, just miniaturized. The Watch D2 uses an ultra-narrow 26.5 mm mechanical airbag.⁷ This group measures pressure. It doesn't guess.

The second is cuffless optical, and it's how most of them work: Galaxy Watch, WHOOP, Oura, Aktiia/Hilo. There's no cuff at all. That green or red light under the watch (the PPG sensor, photoplethysmography, the same one that counts your heartbeats) captures the shape of your pulse wave, and an algorithm estimates systolic and diastolic from it.¹ Because the watch doesn't measure pressure directly, it has to be calibrated against an actual arm cuff. On the Galaxy Watch that's three cuff readings within 30 minutes, fed into the Samsung Health Monitor app, plus mandatory recalibration every 28 days.¹

The third is tonometry, which uses force sensors against the skin instead of light (LiveMetric works along these lines). Still cuffless, but different physics.

The line that matters: group one measures, groups two and three estimate. All the controversy spins around that.

Why estimating is so hard

The optical method's weak spot is structural. Because the estimate leans on a calibration and on demographic data, it tends to pull readings back toward the point where you calibrated, instead of catching the real swings of your day. Arm position, temperature, skin tone, third-party straps, and time since the last calibration all degrade the result.¹⁷ That's why the watch keeps nagging you to recalibrate. And it's why so many users find the whole thing ironic: I bought the watch precisely so I'd never touch a cuff, and now I need a cuff to make it work.

A scientific caveat is owed here, because Samsung has a strong study in its pocket. A paper in the European Heart Journal — Digital Health validated the Galaxy Watch's PPG against invasive catheter measurement in 114 participants and found a high correlation for continuous central pressure (systolic r=0.93).¹⁵ But read the fine print: that's continuous central pressure, validated against a catheter, not the pharmacy scenario. The study shows you can detect meaningful pressure swings with good time resolution. It does not say the watch is as accurate as an arm cuff.

The regulatory knot

This is where it gets fun, because the FDA sent opposite signals in the same year.

On July 14, 2025, the agency hit WHOOP with a warning letter: the "Blood Pressure Insights" feature was neither cleared nor approved, and giving daily systolic/diastolic estimates is, in the FDA's words, "inherently associated with the diagnosis of hypo- and hypertension."⁸ Translation: call it wellness all you like, but estimating pressure is a medical-device function. WHOOP refused to back down, branding BPI a "wellness feature," and as of May 2026 the standoff was still unresolved.¹¹ On September 16, 2025, the FDA doubled down with a public safety communication warning that many over-the-counter blood-pressure gadgets lack agency authorization, and that inaccurate readings can lead to misdiagnosis.⁶

Then came the twist. In January 2026, the FDA loosened its grip: it published revised "general wellness" guidance permitting blood-pressure and glucose products to be marketed without authorization, as long as they're sold as wellness with no medical claim. Commissioner Marty Makary said the agency would "get out of the way" of products that make no medical claims.¹² Days later, on January 23, it also issued a draft guidance specifically for cuffless devices, spelling out how to validate the accuracy of these watches and rings.¹³

The read on both moves: the FDA is tightening against unauthorized medical claims while opening the door to the "wellness estimate" framing. It's a gray zone, and the manufacturers have learned to live in it.

Who's actually been through real scrutiny: the Omron HeartGuide has held 510(k) clearance since November 2018, costs $499, and is medical-grade oscillometric.³ ⁴ And in July 2025 the Aktiia/Hilo became the first cuffless monitor the FDA cleared for over-the-counter sale, with monthly dock calibration and validation across skin tones.⁵ The Huawei Watch D2 is certified as a medical device in Europe (CE-MDR) and validated by STRIDE BP, but still has no FDA clearance.⁷

What the community is saying

On the forums the mood is polarized, and skepticism dominates among the people who actually understand the subject. (Treat everything below as community opinion, not fact. Direct thread access was limited, and some of this is reconstructed from searches across r/Hypertension, r/wearables, r/whoop, and Samsung forums.)

In r/Hypertension, the default stance unwittingly echoes the AHA itself: cuffless is great for spotting a trend over weeks, useless for a single point-in-time number. If you genuinely have hypertension, don't swap the arm cuff for the wrist. The most telling report came from the Samsung community forums: one user calibrated a Galaxy Watch 4 and a Watch 6 at the same time with different values, then noticed each watch started showing readings stubbornly close to its own calibration point, rather than real variation. That's exactly the symptom skeptics flag: the device replays the calibration, it doesn't measure. In r/whoop, the community splits between "it's just wellness, let us use it" and "refusing to pull the feature after a warning letter is arrogance that splashes onto everyone."

On the other side, the convenience crowd has a fair point: a perfect instantaneous number matters less than watching your pressure climb over weeks. And the watch you actually wear, while the cuff stays in the drawer.

Verdict

Don't conflate the three types, because the packaging works hard to conflate them. If you want a reliable number for diagnosis or medication adjustment, the medical consensus is clear: the 2025 AHA/ACC guidelines recommend against cuffless devices for diagnosing and managing hypertension, citing lack of validation.¹⁷ The arm cuff remains the standard, full stop. The optical watch is for catching a trend and feeding curiosity, not for replacing your cardiologist.

The real-cuff wrist devices (Omron, Huawei) are a different conversation. They genuinely measure, with a recognized method, but they pay for it in bulk, battery life, and, in Omron's case, $499. Cuffless technology is genuinely promising, and the Galaxy Watch study shows the path exists. But "promising" and "ready to tell you whether you're hypertensive" are different things, and anyone blurring the two is selling, not measuring.

Sources

1. How to Measure Blood Pressure Using a Galaxy Watch · Samsung Gulf · https://www.samsung.com/ae/support/apps-services/how-to-measure-blood-pressure-using-a-galaxy-watch/ · accessed 2026-06-19
2. Galaxy Watch Guide: How To Measure Your Blood Pressure (And Which Models Can Do It) · SlashGear · https://www.slashgear.com/1753211/samsung-galaxy-watch-how-measure-blood-pressure-which-models-have-feature/ · accessed 2026-06-19
3. Omron's smartwatch blood pressure monitor cleared by FDA, launches in January · MobiHealthNews · https://www.mobihealthnews.com/news/omrons-smartwatch-blood-pressure-monitor-cleared-fda-launches-january · Dec 2018
4. FDA-cleared, wearable blood pressure device hits market · MedTech Dive · https://www.medtechdive.com/news/fda-cleared-wearable-blood-pressure-device-hits-market/544908/ · 2018-12-21
5. Aktiia's Hilo Band Becomes First Cuffless Blood Pressure Monitor Cleared by FDA for Over-the-Counter Use · PR Newswire (Aktiia) · https://www.prnewswire.com/news-releases/aktiias-hilo-band-becomes-first-cuffless-blood-pressure-monitor-cleared-by-fda-for-over-the-counter-use-302501123.html · 2025-07-14
6. Do Not Use Unauthorized Devices for Measuring Blood Pressure: FDA Safety Communication · U.S. FDA · https://www.fda.gov/medical-devices/safety-communications/do-not-use-unauthorized-devices-measuring-blood-pressure-fda-safety-communication · 2025-09-16
7. HUAWEI WATCH D2 (official product page, specs) · Huawei Global · https://consumer.huawei.com/en/wearables/watch-d2/ · accessed 2026-06-19
8. WARNING LETTER — WHOOP, Inc. (709755) · U.S. FDA · https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/whoop-inc-709755-07142025 · 2025-07-14
9. WHOOP receives warning letter from FDA for Blood Pressure Insights · MobiHealthNews · https://www.mobihealthnews.com/news/whoop-receives-warning-letter-fda-blood-pressure-insights · Jul 2025
10. Whoop Refuses to Pull Blood Pressure Tool After FDA Warning · Bloomberg · https://www.bloomberg.com/news/articles/2025-08-14/whoop-refuses-to-remove-blood-pressure-tool-despite-fda-warning · 2025-08-14
11. After warning letter, Whoop and FDA in discussions about controversial blood pressure feature · STAT News · https://www.statnews.com/2026/05/21/whoop-has-not-resolved-fda-dispute-over-blood-pressure-feature/ · 2026-05-21
12. Blood pressure wearables flood the market after FDA relaxes oversight, concerning experts · The Boston Globe · https://www.bostonglobe.com/2026/05/28/business/whoop-samsung-oura-fda/ · 2026-05-28
13. Cuffless Non-Invasive Blood Pressure Measuring Devices — Clinical Performance Testing and Evaluation; Draft Guidance · Federal Register / U.S. FDA · https://www.federalregister.gov/documents/2026/01/23/2026-01288/cuffless-non-invasive-blood-pressure-measuring-devices-clinical-performance-testing-and-evaluation · 2026-01-23
14. Discover the world's first smartwatch with medically certified 24/7 blood pressure monitoring · TechRadar · https://www.techradar.com/health-fitness/smartwatches/discover-the-worlds-first-smartwatch-with-medically-certified-247-blood-pressure-monitoring · accessed 2026-06-19
15. Feasibility and performance evaluation of PPG on a Galaxy Watch in continuous central blood pressure monitoring · European Heart Journal — Digital Health · https://academic.oup.com/ehjdh/advance-article/doi/10.1093/ehjdh/ztag008/8432238 · 2026-01-21 · DOI: 10.1093/ehjdh/ztag008
16. Cuffless blood pressure technologies in wearable devices show promise to transform care · American Heart Association Newsroom · https://newsroom.heart.org/news/cuffless-blood-pressure-technologies-in-wearable-devices-show-promise-to-transform-care · Dec 2025
17. Cuffless Devices for the Measurement of Blood Pressure: A Scientific Statement From the American Heart Association · Hypertension (AHA) · https://www.ahajournals.org/doi/10.1161/HYP.0000000000000254 · Dec 2025 · PMID: 41376592 · DOI: 10.1161/HYP.0000000000000254
18. The quest for accurate wearable blood pressure monitors · Hypertension Research (Nature) · https://www.nature.com/articles/s41440-025-02410-w · 2025

Community (opinion, not source): r/Hypertension, r/wearables, r/whoop, r/GalaxyWatch, and the Samsung community forums. Direct thread access was limited; sentiment is an approximate reconstruction from searches across those communities.

— Newsroom, Acta Verum