Apple Watch Red Light: What Is It? And How to Turn it Off

Quick Answer:

The red light under an Apple Watch illuminates the skin and measures light reflection to determine blood oxygen (SpO2) levels.

If you’ve noticed a red light shining underneath your Apple Watch and are wondering what it is, don’t be alarmed, you’re in the right place. The red light on the back is a vital feature built in to the watch.

Let’s take a closer look at how the red light works, what it’s used for, and how you can disable it.

Apple Watch Red Light, What is it?

The red light under an Apple Watch is a feature specifically for measuring your blood oxygen (O2) levels, per Apple.

Important! This functionality distinctly sets it apart from the green light, which focuses on capturing your heart rate data.

Blood oxygen levels are essential as they provide insights into how effectively your lungs are delivering oxygen to your bloodstream.

Your Apple Watch then uses this data to ensure you have accurate health metrics provided to you throughout the day.

How to Turn Off the Red Light on Apple Watch

Turning off the red light under an Apple Watch will result in your watch no longer blood oxygen levels.

Knowing that, follow these instructions:

1. Open “Settings” on your Apple Watch.
2. Select “Blood Oxygen“.
3. Toggle off “Blood Oxygen Measurements“.

Which Apple Watches Read Blood Oxygen?

Apple Watch Series 6, Series 7, SE, Series 8, Series 9, Ultra, and Ultra 2 are all capable of reading blood oxygen (O2) levels.

Apple Watch Series 3, Series 4, and Series 5 are not capable of measuring O2.

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