Your smartphone cannot reliably check your blood pressure on its own. Despite apps that claim otherwise, no current iPhone or Android phone has a built-in sensor capable of accurately measuring blood pressure. The American Heart Association’s 2025 guidelines explicitly recommend against using cuffless devices for diagnosing or managing high blood pressure until the technology proves more reliable. What your phone can do is help you track and log readings taken with a traditional cuff, and certain Samsung smartwatches offer a limited blood pressure feature that still requires a cuff for setup.
How Phone-Based Blood Pressure Apps Claim to Work
Most smartphone blood pressure apps use your phone’s camera and flash to detect tiny changes in blood flow through your fingertip. You press your finger against the rear camera, the flash illuminates the skin, and the camera picks up subtle color shifts as blood pulses through your arteries. This produces a waveform called a photoplethysmography (PPG) signal, which the app then analyzes to estimate blood pressure based on features like pulse width, the slope of each heartbeat’s upstroke, and the timing between pulses.
A more advanced approach skips the finger entirely. Using the front-facing camera, some apps record a short video of your face and analyze imperceptible changes in skin color caused by blood flowing beneath the surface. One version of this technology, called Transdermal Optical Imaging, divides the face into 17 regions and uses machine learning to extract blood pressure estimates from the combined signals. In a study of 1,328 adults with normal blood pressure, this method came within about 0.4 mmHg of reference readings for systolic pressure and 0.2 mmHg for diastolic, with standard deviations of roughly 7 and 6 mmHg respectively.
Those numbers sound promising, but they come with a critical caveat: the study only included people who already had normal blood pressure. The technology has not shown the same performance in people with hypertension, which is the population that actually needs accurate readings.
Why These Readings Aren’t Trustworthy Yet
The gap between a lab demonstration and a clinically useful tool is enormous. The American Heart Association’s scientific statement on cuffless devices lays out several problems. Studies have shown that cuffless blood pressure devices perform poorly at tracking the kinds of changes that matter most: blood pressure shifts during exercise, during sleep, in response to medication, and during everyday activities. In some cases, the devices were no more accurate than simply guessing based on a person’s age, weight, and a single prior cuff reading.
Variability is the core issue. Even among more established cuffless technologies (like finger-cuff devices used in hospitals), large-scale comparisons against direct arterial measurements found that inaccuracies led to unnecessary medical interventions in 0.1% to 3% of surgical patients. For a smartphone app using only a camera, the margin of error can be even wider. Studies in children found differences of up to 20 mmHg between cuffless and standard readings within the same person, which is the difference between a normal reading and one that looks like hypertension.
It’s also worth knowing that FDA clearance doesn’t guarantee accuracy. The FDA reviews performance data but does not require formal clinical validation testing using an established protocol. So a “cleared” app is not the same as a proven one. Nearly 80% of even traditional cuff-based monitors on the global market have never published results from formal accuracy testing.
What Samsung Galaxy Watches Actually Offer
Samsung’s Galaxy smartwatches (running Wear OS 4.0 or later) include a blood pressure feature through the Samsung Health Monitor app. This is the closest any mainstream consumer device gets to phone-based blood pressure measurement, but it requires more setup than most people expect.
To use it, you need a traditional upper-arm cuff monitor. The calibration process requires you to take three cuff-based readings within a 30-minute window and enter those values into the app. Before calibrating, Samsung instructs you to avoid smoking, bathing, exercising, alcohol, and caffeine for at least 30 minutes. You sit in a chair with your back supported, feet flat, arm resting on a table, and stay still for five minutes before beginning.
After calibration, the watch uses its optical sensor to estimate blood pressure going forward. But the watch is essentially adjusting its optical readings based on your cuff measurements. You need to recalibrate periodically, and the feature is only available in certain countries. It’s a convenience tool for tracking trends between cuff readings, not a replacement for actual measurement.
What iPhones Can and Can’t Do
The iPhone has no blood pressure measurement capability whatsoever. Apple’s Health app lets you log blood pressure readings manually, but you need a separate cuff to get the numbers. To record a reading, open the Health app, tap Search, then Heart, then Blood Pressure, and tap Add a Measurement. You enter the date, time, systolic value, and diastolic value yourself.
Some Bluetooth-enabled arm cuffs can sync directly with Apple Health or Google Fit, which saves you the manual entry step. But the phone itself is just storing and displaying the data. It is not generating the reading.
Using Your Phone to Track Blood Pressure
Where smartphones genuinely help is in organizing your readings over time. Research published in the AHA’s journal Hypertension found that app-assisted home blood pressure monitoring, where patients use a cuff at home and log results through a phone app, can improve medication adherence, strengthen communication with doctors, and lead to better blood pressure control. The combination of regular self-measurement plus digital tracking and sometimes teletransmission of results to a care team appears to be more effective than office visits alone.
App-assisted home monitoring also showed high sensitivity as a screening tool for sustained and masked hypertension, meaning it’s good at flagging when something might be wrong. However, researchers noted it should not be relied on for making a final diagnosis of any hypertension subtype. It works best as a complement to clinical evaluation, not a substitute.
What Actually Works for Home Monitoring
An automatic upper-arm cuff remains the gold standard for checking blood pressure at home. Wrist cuffs are available but less accurate due to positioning challenges. When choosing a monitor, look for one validated against established accuracy standards. The international standard (ISO 81060-2) requires devices to fall within 5 mmHg average error with a standard deviation of 8 mmHg or less.
Your phone’s role in this process is as a logbook and trend tracker, not a measuring device. Pair a validated cuff with a health app, take readings consistently at the same time of day, and you’ll have a detailed record that’s far more useful to your doctor than occasional office measurements. That combination of a reliable cuff and a smartphone for tracking is, for now, the best version of “checking blood pressure with your phone” that actually works.