The Battery Draining Sensor
Newer Apple Watch models feature a powerful sensor array on the back crystal capable of measuring your blood oxygen saturation (SpO2). By default, the watch does not wait for you to manually open the app; it silently activates the bright red LED sensors periodically in the background throughout the day and night to take automated readings. While this provides a comprehensive health graph in the Health app, powering those red LEDs consumes a massive amount of battery life. If you are struggling to make your Apple Watch last a full 24 hours and you do not have a medical need for constant respiratory tracking, you should disable the background measurements.
How to Turn Off Background Blood Oxygen Tracking
You can disable the automated scanning while keeping the ability to take manual readings when you actually want them.
- Open the Settings app directly on your Apple Watch (the grey gear icon).
- Scroll down the list and tap on Blood Oxygen.
- Under the “Allow Background Measurements” section, you will see two specific toggle switches:
- Toggle In Sleep Focus to Off (this stops the watch from taking readings while you are sleeping).
- Toggle In Theater Mode to Off.
Note: If you want to completely disable the sensor entirely, toggle the master switch at the very top labeled “Blood Oxygen Measurements” to Off.
The Battery Benefits
With the background measurements disabled, the red LEDs will never fire automatically. This instantly reclaims a significant percentage of your daily battery life. If you ever feel short of breath or simply want to check your SpO2 levels, you can still manually open the Blood Oxygen app on your watch face, sit perfectly still, and initiate a manual 15-second scan, giving you full control over when the battery-draining sensors are utilized.