The Background Polling
Modern Apple Watches feature a specialized optical sensor designed to measure your blood oxygen saturation (SpO2). By default, the watch does not only take these measurements when you manually open the app. Instead, it continuously polls the sensor in the background throughout the day and night while you are resting. While this creates a comprehensive health chart, firing the bright red LEDs on the back of the watch hundreds of times a day consumes a noticeable amount of battery life. If you do not have a medical reason to track your blood oxygen constantly, disabling the background schedule can easily extend your battery runtime.
How to Turn Off Background Measurements
You can sever the sensor’s background schedule without disabling the app completely via the Blood Oxygen settings.
- Open the Settings app directly on your Apple Watch (the grey gear icon).
- Scroll down the main list and tap on Blood Oxygen.
- Leave the master “Blood Oxygen Measurements” toggle On if you still want to take manual readings.
- Scroll down to the “Allow Background Measurements” section.
- Toggle In Sleep Focus to the Off position.
- Toggle In Theater Mode to the Off position.
Manual Control Only
The change is instantaneous. The Apple Watch will completely stop firing the red sensor LEDs while you are sleeping or sitting still. The automated polling schedule is permanently deactivated, saving your battery power. The Blood Oxygen app remains fully functional on your watch; however, the sensor will now only activate when you manually open the app and explicitly instruct it to take a reading.