Blood pressure readings have been rumoured for the Apple Watch for a few generations now. Serial leaker Mark Gurman from Bloomberg claims this year will be the year it actually happens.
A few days ago Gurman reported the Apple Watch Series 11 and Watch Ultra 3 will have Apple’s long-awaited blood pressure feature.
However, there are reasons it has taken this long. And while it’s likely to be somewhat limited when it does arrive.
The classic way to measure blood pressure is with an inflatable cuff, a piece of kit known as a sphygmomanometer. It’s used to determine the pressure of blood flow as that flow is blocked through the inflation of the arm-worn cuff, and the pressure when it’s not being restricted — in the final stages of deflating the cuff.
This two-part process determines the diastolic and systolic figures that make up a blood pressure result. Only one mainstream wearable series uses (roughly) this method of blood pressure sensing, the Huawei Watch D2.
It’s a very neat feat of miniaturisation but is not expected to be the method used by Apple.
How Will The Apple Watch Measure Blood Pressure?
Other watches that provide some form of blood pressure measurement rely on the photoplethysmography (PPG) hardware used for all-day heart rate reading. This uses green and red/infrared LEDs to direct light into the wearer’s wrist. And light sensors, acting like tiny cameras, record variations in the reflected light as blood is pumped through the veins.
Using this method to work out the wearer’s heart rate is relatively simple next to doing so for blood pressure, which requires more source information than just the pace at which the heart is beating.
Gurman suggests the Apple Watch Series 11 and Watch Ultra 3 will not actually be used to spit out diastolic and systolic readings, as a $30 cuff solution from Amazon can, but will instead notify you when it looks as though your blood pressure is elevated. It’s a hypertension alert that specialises in change, not straight numerical results.
One key question here is whether Apple’s solution is going to have greater usefulness than a heart-rate based stress indicator that fired out an alert. After all, stress can cause a sharp rise in blood pressure.
Is An Apple Watch PPG Sensor Enough?
Several studies just in the last few years have addressed the use of PPG to analyze blood pressure, and a Nature paper from 2019 detail the ways several promising applications of the concept fall apart either through limited accuracy or requiring multiple sites of PPG recording.
This is where the concept of the long-rumoured Apple ring gets more interesting. Multi-site PPG readings could lend more substance to the Apple Watch as a blood pressure monitor. But in November 2024 Gurman claimed Apple “has no plans to launch” a smart ring.
A single-site PPG sensor is highly limited when you stop to think about it. In the context of heart rate, the lack of well-defined context doesn’t matter too much. The sensor doesn’t know which part of the wrist it’s looking at, where it is relative to the veins in the wrist, or how the colour of the person’s skin may be affecting the reflected light.
For heart rate that may not matter too much, but it does for blood pressure.
However, a paper published in 2024 detailed a hardware-based system using a PPG sensor for both heart rate and blood pressure recording. And it found it was able to detect hypertension with an accuracy of 92.42%, with the help of machine learning algorithms that estimate blood pressure from limited raw information.
A diagram from an Apple patent
Apple
Also in November 2024, the U.S. patent office registered an Apple patent detailing am Apple watch that could utilize an inflatable strap that acts as a “sensing chamber” much like that of a traditional blood pressure cuff. The difference here, though, is the medium used to inflate the chamber is a liquid rather than air.
It’s an interesting, and complicated-sounding, piece of tech to fit inside a watch. But the vast majority of techy patents never end up as — and were never intended be —actual products.
What’s the takeaway? It’s no wonder Apple has taken years to include blood pressure readings in the Watch family, even though Samsung brought it to the Galaxy Watch 4 in 2021. The main hope is Apple’s slower approach will mean users won’t need to regularly calibrate readings with a more conventional blood pressure cuff.
Apple is expected to announce the Apple Watch models with blood pressure readings — the Series 11 and Ultra 3 — in September.