Measure blood oxygen levels on Apple Watch
Use the Blood Oxygen app 
on Apple Watch Series 6 or later to measure the percentage of oxygen your red blood cells carry from your lungs to the rest of the body. Knowing how well oxygenated your blood is can help you understand your overall health and wellness.
Note: The Blood Oxygen app is not available in all regions. Blood Oxygen app measurements are not intended for medical use.
Set up Blood Oxygen
Open the Settings app
on your Apple Watch.Tap Blood Oxygen, then turn on Blood Oxygen Measurements.
Turn off background measurements when the Sleep Focus or theater mode is active
Blood oxygen measurements use a bright red light that shines against your wrist, which may be more visible in dark places. You can turn off measurements if you find the light distracting.
Open the Settings app
on your Apple Watch.Tap Blood Oxygen, then turn off In Sleep Focus and In Theater Mode.
Measure your blood oxygen level
The Blood Oxygen app periodically measures your blood oxygen level throughout the day if background measurements are turned on, but you can also take an on-demand measurement at any time.
Open the Blood Oxygen app on your Apple Watch.
Rest your arm on a table or in your lap, and make sure your wrist is flat, with the Apple Watch display facing up.
Tap Start, then hold your arm very still during the 15-second countdown.
At the end of the measurement, you receive the results. Tap Done.
Note: The back of your Apple Watch needs skin contact. Wearing your Apple Watch not too tight or too loose, with room for your skin to breath, helps ensure successful Blood Oxygen measurements. For more information, see the Apple Support article How to use the Blood Oxygen app on Apple Watch.
View your Blood Oxygen measurements history
Open the Health app on your iPhone.
Tap Browse, tap Respiratory, then tap Blood Oxygen.
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