Can Smartwatches Really Measure Blood Pressure Without a Cuff?

Why it sounds plausible

Each heartbeat changes the pressure and volume of blood in an artery. Optical sensors can detect the pulse-related changes in light absorption; other devices use different signals. Algorithms then estimate pressure from those signals, sometimes using personal characteristics and a comparison with a conventional cuff. The technology is plausible, but it is estimating a quantity through a model. [1]

What calibration can and cannot establish

Some devices need initial and repeated calibration against a cuff. An error in the reference measurement can therefore enter the estimate. A model may agree soon after calibration yet struggle when pressure changes for reasons that also alter the underlying signal. A sequence of plausible-looking numbers is not, by itself, proof that genuine changes are being tracked. [1]

This is why validation needs to examine more than average agreement while someone sits still. Arm position, movement, sleep, skin characteristics and time since calibration may matter. Researchers also need to test whether the device follows changes after treatment rather than simply returning values near its calibration point. [1]

What current scientific guidance says

The American Heart Association's scientific statement, published online in December 2025 and in Hypertension in 2026, describes considerable promise alongside unresolved accuracy and real-world validation problems. It supports caution about using cuffless devices for diagnosis or treatment decisions. This is an expert synthesis of the evidence, not a trial showing that every cuffless device fails. [1]

The FDA separately warned in September 2025 against unauthorised devices claiming to measure blood pressure, including wearable features. Inaccurate readings can create false reassurance or prompt inappropriate action. That warning concerns unauthorised devices; it should not be stretched into a claim that no authorised cuffless technology exists. [2]

The catch: clearance is specific, and alerts are different

A regulatory decision concerns a particular product, software version, population and intended use. A spot-check authorisation is not automatically evidence for continuous readings during exercise or sleep. Nor does a brand's authorised feature validate an unrelated app or feature on the same device. [1][2]

Apple's hypertension-notification feature, for example, is designed to identify patterns suggesting possible hypertension rather than supply systolic and diastolic measurements. Its instructions direct users towards cuff measurements and discussion with a healthcare professional after an alert. Treating that as a cuffless numerical blood-pressure monitor would misdescribe the feature. [3]

What this means for you

For checking or managing blood pressure, use an appropriately validated upper-arm cuff and follow the measurement method recommended by your clinician. A watch alert can prompt a proper check; it should not be used to start, stop or adjust medication. [1][2]

If considering a cuffless product, look for evidence on the exact model, calibration schedule, intended population and conditions tested. Even trend monitoring needs validation: a trend that follows an algorithm's assumptions rather than your pressure can be misleading.

Research & Sources

Check the evidence yourself. Access limitations and indirect evidence are identified below.

Evidence reviewed: October 2026

Targeted editorial review of sources available on 24 October 2026, not an exhaustive systematic review. Evidence vs Hype provides education, not individual medical diagnosis or treatment. Original AI-generated artwork is illustrative and does not show a study result. No commercial product was selected or endorsed.