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Why Does My Apple Watch Light up Red When I’m Not Wearing It?

Last Updated Dec 5, 2022
Apple Watch on Desk

If you have an Apple Watch, no matter what generation, you probably have seen flashing lights on the backside of the watch. Though the red light may seem concerning, it’s not what you think!

Your Apple Watch lights up red when you’re not wearing it because it is trying to measure your blood oxygen. You most likely have “background measurements” turned on, which allows your Apple Watch to read your blood oxygen levels anytime.

In this article, we’ll cover more about the red lights you see on your Apple Watch, what they mean, and why they are important for the Apple Watch’s functionality!

Why Does My Apple Watch Light Up Red?

Upon first glance, this feature can definitely be unsettling!

Your Apple Watch may be lighting up red even when you aren’t wearing it because Apple Watches have a Background Measurements feature. This feature continues to run the blood oxygen measurements even when it is off your wrist because it may think you are simply standing still.

Should I Turn Background Measurements Off?

If you want to avoid the red lights, you can turn it off using the following steps:

  • Start by pressing the Digital Crown on the Apple Watch – this will take you to your apps.
  • Select settings then proceed to blood.
  • Within the Blood section of settings, switch off for the blood exogenous measurements. 

Now, your Apple Watch will stop measuring your blood oxygen levels. At any time, you can go in and turn it back on in the settings menu!

What Is That Red Light on My Apple Watch?

The Apple Watch uses LED lights and infrared lights that are actually not visible to illuminate on a person.  The photodiodes then measure the amount of light that is reflected onto the watch.

The Apple Watch uses the data provided to identify the color of the user’s blood, which is how the oxygen level is determined.

In order for the technology to work, the watch must at least be a Series 6, running the watchOS7 and paired to an iPhone running iOS14 software.

The Blood Oxygen App

The blood oxygen app allows users to measure the oxygen levels of your blood. This provides users with insights to their overall wellness in an instant.

When using the app, it is important to know what the normal levels are for blood oxygen, which is typically 95 – 100%.

Everybody is different however, and some people are able to live with blood oxygen levels below 95%.

 Furthermore, people tend to experience lower than 95% while they are sleeping.

Of course, the app is not designed for official medical use, it is geared more towards the user’s general fitness and well-being.

Will the Blood Oxygen App Work with my Apple Watch?

If you are unsure what is necessary for the app to work on your technology, use the following steps for reference:

  • Ensure the app is available within your country or region, this will be established during setup. If the app is not available at your location, you will not be able to use the app.
  • Ensure you are using an iPhone 6 or newer model. Furthermore, you must have the latest version of the iOS.
  • To make sure the Apple Watch will pair with the iPhone, the watch must be at least an Apple Watch Series 6, 7, 8, or Ultra – with the latest version of the WatchOS.
  • Finally, you must be at least 18 years or older to use the app – minors are unable to use this application as it is prohibited within their Health Profile on the iPhone.

Following these steps will help you get set up without issue and stay connected so your readings are always accurate!

Setting up the Blood Oxygen Application

Once you are sure your technology is up to date and you are ready to start setting up the application, use the following steps to ensure you are setting up the app correctly.

  1. You will need to open the Health app on your iPhone and follow the on screen steps.
  2. On screen steps: the typical on-screen steps are as follows – Respiratory > Blood Oxygen > Enable
  3. On Watch: once the app is set up on your phone, head to your watch and open the blood oxygen app and measure your blood oxygen levels.

How to Take Your Blood Oxygen Levels on Apple Watch

Once you have everything set up on your phone and watch, you are now able to follow these steps to measure your blood oxygen levels

  1. Have the Apple Watch securely on your wrist as you normally would.
  2. Open the Blood Oxygen app on your Apple Watch
  3. You must stay still, and ensure your wrist is completely flush and that the screen of the Apple Watch is face up.
  4. Once set up, tap start, the app will run the tests for about 15 seconds
  5. After you run the test, you will have to wait another 15 seconds to have the results completed
  6. Tap done, and you are then able to look at your results on your iPhone.

This is when that red light will come on, even though you can’t see it.

If you see it on when you’re not wearing it, it’s just the Apple Watch trying to measure your blood oxygen because it thinks you’re standing still.

Turning off the red light

If you want to avoid the red lights, you can turn it off using the following steps:

  • Start by pressing the Digital Crown on the Apple Watch – this will take you to your apps.
  • Select settings then proceed to blood.
  • Within the Blood section of settings, switch off for the blood exogenous measurements. 

Now, your Apple Watch will stop measuring your blood oxygen levels. At any time, you can go in and turn it back on in the settings menu!

Conclusion

If you have been wondering what the red lights are on the back side of your Apple Watch, you may not be wondering anymore!

These red lights, created by a combination of LED and infrared lights to read your blood oxygen levels.

There are a few requirements in terms of technology, like at least an Apple Watch 6 or newer, along with the iPhone 6 or newer.