How to measure blood oxygen on Apple Watch

Just got the Apple Watch Series 6 and want to check your "wellness" with the new blood oxygen sensor? Here's how to do it.

The Apple Watch Series 6 has a blood oxygen monitor for measuring oxygen saturation levels (SpO2). As we said in our review of the smartwatch, the feature is not meant to replace your doctor. The measurement is only a "key indicator of your overall wellness" according to Apple.

Despite not being particularly useful right now — Apple is working with researchers to find potential links to health problems like asthma, respiratory issues including the flu or COVID-19, or heart failures — an SpO2 reading may put you at ease during these unpredictable times.

Raymond Wong / Input

Step 1

Open the Blood Oxygen app and tap the start button. To get a successful reading, you want the sensor to be wrapped snuggly around your wrist. It doesn't need to be tight, but it shouldn't be loose. Just right. You'll know it after a few tries.

Raymond Wong / Input

“During a blood oxygen measurement, the back crystal shines red and green LEDs and infrared light onto your wrist. Photodiodes then measure the amount of light reflected back.”


Step 2

After 15 seconds, the app will give you an SpO2 percentage. According to Apple "The majority of people have a blood oxygen level of 95 - 99%. However, some people live a normal life with blood oxygen levels below 95%."

Raymond Wong / Input

Step 3

If the watch says your reading was unsuccessful, try the following:

• Tighten your watch band

• Move your watch higher up on your wrist

• Rest your hand on a flat surface like a tabletop and hold it as steady as possible

Raymond Wong / Input

Another way to take a reading: put your finger directly under the blood oxygen sensor, making sure to cover it entirely and hold steady. As tech YouTuber Dave2D, who also works with medical equipment as his day job, notes in his video, taking an SpO2 reading this way is often as accurate as a pulse oximeter. He said he didn't have as many failed readings as on his wrist.

Low SpO2 reading?

Don't panic if the Apple Watch tells you your SpO2 reading is below the "normal 95-99%" range. It could mean anything. Keep monitoring your blood oxygen and if you see a pattern of low readings, then maybe there's something to be concerned about. Bring your data to your doctor and then go from there.

Again, it's unclear if there's any real practicality to the Series 6's blood oxygen monitor. For most people, an SpO2 reading isn't valuable since it doesn't suggest any direct correlation to any specific health issues. But if you just got a Series 6 and can't figure out how to get an SpO2 measurement, now you know.

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