Apple Watch and blood pressure: what the watch really does

Since watchOS 26, the Apple Watch can notify you of possible high blood pressure – in Germany and the EU since the end of September 2025. Searches for “Apple Watch 11 measure blood pressure” have practically exploded since then.

Behind this lies a stubborn misunderstanding: The watch does not measure your blood pressure, and it does not show you a reading. The display never shows 128 over 82. What it does is something else – and it is genuinely useful once you know what you are holding.

What the feature actually does

The feature is called Hypertension Notifications. It runs passively in the background and analyses data from the optical heart sensor – the green light on the underside of the case that registers changes in blood volume in the wrist.

It does not evaluate a single snapshot, but a 30-day window. During this period, the watch looks for patterns in how the blood vessels respond to each heartbeat – patterns that typically occur with chronically raised blood pressure.

If it finds such patterns, you receive a notification. This notification contains no reading, just a prompt to check again with a proper cuff.

That is also why it takes at least 30 days after activation before the first possible notification. Anyone who sets up the watch on Friday and expects a blood pressure display on Saturday will look in vain.

Who can use the feature at all

• Apple Watch Series 9, 10 and 11 as well as Ultra 2 and Ultra 3. The Apple Watch SE is not included.
• watchOS 26 or later, paired with iOS 26 or later.
• Aged 22 and over and without an existing diagnosis of high blood pressure – people already being treated are not the target group of the feature.
• Not intended for use during pregnancy. High blood pressure in pregnancy is a distinct and serious situation that belongs under medical care, not on a wrist.

How often the watch is right – and how often it isn’t

Here it is worth looking at the figures – specifically those published by Apple itself. The validation study for the feature reports two values:

• Sensitivity 41.2 per cent. So of 100 people who actually have high blood pressure, around 41 receive a notification – and around 59 do not. For more pronounced high blood pressure (stage 2), the figure rises to 53.7 per cent.
• Specificity 92.3 per cent. Of 100 people without high blood pressure, around 8 still receive a notification.

An analysis published in JAMA in 2026 extrapolated these figures to a representative population sample and reached the same picture: around 59 per cent of adults with undiagnosed high blood pressure would not receive a notification.

This is neither a scandal nor a criticism of Apple – the company publishes these figures itself and explicitly points out during setup that not everyone with high blood pressure will receive a notification. It is simply the nature of a screening tool that works from an indirect signal.

The most important sentence about this feature

A notification means: measure again. No notification does not mean: everything is fine.

When almost six in ten of those affected slip through the net, the absence of a notification is no reason to relax. Anyone who has symptoms, a family history, or has not known their blood pressure for years should measure it – regardless of what the watch says or doesn’t say.

What a notification means in your case

It gets interesting when you ask: how likely is high blood pressure after the watch has sent a notification? The JAMA analysis shows that the answer depends heavily on who you are:

• For people under 30, a notification raises the probability from around 14 to about 47 per cent. So even here, a notification still means that roughly every second person does not have high blood pressure at all.
• For people over 60, it rises from around 45 to about 81 per cent. Here, a notification should be taken much more seriously.

This is not a quirk of this watch but basic arithmetic for any screening: the rarer a condition is in a group, the more false alarms the same test produces. In practice, it means one thing above all – don’t panic after a notification, but measure again properly.

What you should do after a notification

Apple’s own recommendation matches what professional societies have long advised: measure with an upper-arm cuff for one week, in the morning after getting up and in the evening before going to bed.

1. Sit quietly for five minutes before each measurement. Without these five minutes, you are measuring your day, not your blood pressure.
2. Cuff on the upper arm, at heart level, correct size, device validated according to DIN EN ISO 81060-2.
3. Take two measurements one to two minutes apart each time and write both down.
4. Keep going for seven days – even if day three looks good.
5. Take the sheet with you to your doctor’s appointment.

The most common mistakes are covered in Measuring blood pressure correctly: 7 mistakes that distort your readings. What matters when choosing a device is explained in Which blood pressure monitor is the most accurate?

And if you are wondering why two measurements taken in quick succession differ: that is normal and explained in Why your blood pressure is different every time you measure it.

If you are considering buying a blood pressure wearable as well: the seven questions in Buying a blood pressure wearable: 7 questions before you decide put manufacturers’ claims into context before you make your choice.

Why the watch cannot show a reading

A cuff does something physically unambiguous: it compresses the artery and releases the pressure in a controlled way. The pressure at which blood flows again is the blood pressure – measured in the same unit in which it is stated.

An optical sensor on the wrist sees none of this. It sees changes in brightness from which the shape of the pulse wave can be derived. From this, a pattern can be inferred statistically, but no pressure in millimetres of mercury can be derived. That is exactly why Apple does not output a number – an honest decision, not a technical gap that the next update will close.

We have written about this difference in principle in Measuring blood pressure with a smartwatch: what the watch can really do.

Other wristbands take the opposite approach and do show numbers – after being “calibrated” once against a cuff device. Why this does not create accuracy but simply inherits the uncertainty of the reference device is explained in What “calibrated” really means for a blood pressure wearable.

And for those who want to manage without any device at all: feeling the pulse, interpreting symptoms, apps without a cuff – which of these methods provide a blood pressure reading and which do not is covered in Measuring blood pressure without a device – is it possible?

What the feature is still good for

It reaches people who would otherwise never measure. High blood pressure does not hurt; many people are unaware of it for years. A watch that prompts 41 per cent of those affected to measure at all is worth more than no prompt – provided the prompt is actually followed by a proper measurement.

As a screening entry point: useful. As proof that everything is fine: unsuitable. As a basis for treatment decisions: certainly not.

When you should seek medical advice

• After a notification from the watch – with a week of documented cuff readings in hand
• If your self-measured readings are repeatedly at or above 135/85 mmHg
• If you have headaches, visual disturbances, shortness of breath, dizziness or a racing heart – regardless of any watch

In the event of a sudden severe headache, chest pain, speech or vision problems, or one-sided paralysis: call the emergency services immediately on 112 (the European emergency number).

Never change existing blood pressure medication based on what a watch shows or does not show.