blood oxygen
If you own an Apple Watch Series 6 or 7 and have watchOS 7 or later, a built-in oximeter measures your blood oxygen level, which can tell you if you’re getting enough oxygen to your brain and other vital organs. A typical reading should be somewhere between 95% and 100%. A low percentage of oxygen in the blood can be a sign of a pulmonary or cardiac issue, or other related problem.
To set up the Blood Oxygen sensor, open the Watch app on your iPhone and tap Blood Oxygen. Make sure the switch for Blood Oxygen Measurements is turned on. Here, you can also control when the sensor takes background readings by enabling or disabling In Sleep Mode and In Theater Mode.
To take a reading, open the Blood Oxygen app on your watch and tap the Start button to begin the scan. The sensor begins with a 15-second countdown. If the measurement is successful, the screen will then indicate the percentage of your blood oxygen level. For best results, make sure your watch is not too low on your wrist and that the band is snug but comfortable. Keep your hand and wrist as still as possible during the reading.
While you shouldn’t rely on this sensor as your sole source of information on your blood oxygen level, it can at least tip you off to any problems that you can then discuss with your doctor.