How to Disable Blood Oxygen Background Measurements on Apple Watch

The Red Sensor Drain

Select models of the Apple Watch feature a Blood Oxygen sensor built directly into the back crystal. By default, the watch doesn’t just use this sensor when you manually open the app; it actively takes background readings throughout the entire day and night. If you look at your wrist while sitting at your desk, you might randomly see bright red LED lights glowing against your skin. While tracking blood oxygen during sleep can be a useful health metric, forcing the watch to fire up these powerful red LEDs every few hours during the day places a continuous, unnecessary strain on the battery. If you are struggling to get your watch to last a full 24 hours, you should disable these automated background checks.

How to Turn Off Background Measurements

You can revoke the watch’s permission to run the sensor passively via the Blood Oxygen settings.

1. Open the Settings app directly on your Apple Watch (the grey gear icon).
2. Scroll down the main list and tap on Blood Oxygen.
3. Scroll down to the section labeled “Allow Background Measurements.”
4. You will see two specific toggle switches:
5. Toggle In Sleep Focus to the Off position (this stops the red lights from flashing while you are trying to sleep).
6. Toggle In Theater Mode to the Off position (this stops the red lights from flashing in a dark movie theater).

Manual Control Restored

The change is instantaneous. The red LED array on the back of your watch will completely cease firing on its own schedule, instantly improving your daily battery life. The sensor itself is not disabled; if you ever want to check your SpO2 levels, you can simply tap the Blood Oxygen app on your honeycomb grid and manually initiate a 15-second scan, guaranteeing the battery is only used when you explicitly request it.