Image source: Fitbit

Using the Fitbit SpO2 sensor to track blood oxygen, what you need to know

The SpO2 Fitbit sensor can be used to track your blood oxygen levels while you sleep. A number of watches and fitness trackers come with the functionality baked in. Here’s everything you need to know.

What is blood oxygen?
Using a Fitbit to detect blood oxygen
Fitbit’s SpO2 clock face
Sleep apnea

What is blood oxygen?

Wearables with an SpO2 sensor have the ability to estimate how much oxygen your red blood cells are carrying. The oxygen is collected from the lungs and delivered to all parts of your body. You want to keep this figure high as possible, as it is vital to your health.

In the past we would say that most people don’t really need to be concerned about their blood oxygen levels. But this has all changed in 2020 with the coronavirus pandemic. Those that contract COVID-19 sometimes see a fall in their blood oxygen levels. If it goes down too much it can be a cause of concern.

Healthy individuals typically register readings above 97%. Measurements should never fall below 95%, although levels above 92% are generally considered safe. The number fluctuates during the day depending on what you are doing. It is therefore best to take measurements while you are resting or overnight.

Indicators of low oxygen levels include shortness of breath, headache, restlessness, dizziness, rapid breathing, chest pain and more. There are medical conditions that can influence this such as asthma, heart disease and more. But also external factors such as altitude.

Using a Fitbit to detect blood oxygen

Those that have a Versa, Ionic, Sense or Charge 3/4 strapped to their wrist, may have noticed a red light shining on the underside of their tracker. This is the SpO2 sensor doing its thing.

Fitbit actively testing PulseOx sensor, no release date in sight
The data is derived from a combination of the red and infrared sensors on the back of the device.

However, despite some Fitbit’s SpO2-packing devices being a number of years old (Ionic was released back in 2017), it is only over the past year that the functionality has been enabled. Now it is becoming a standard and we expect most future Fitbit wearables to come with the functionality baked in.

Garmin was one of the pioneers in this area. The Vivosmart 4, much of the current Forerunner range, and watches in the Fenix range were amongst the first to come with the blood oxygen tracking. Their sensors monitor levels during the night at regular intervals, but also allow users to manually take readings throughout the day. And it works pretty well.

Fitbit actively testing Pulse Ox sensor, no release date in sight
Estimated Oxygen Variation


Fitbit has taken a similar route, although it doesn’t allow for manual readings. As shown in the app screen shot, for those with the feature activated there’s a graph called Estimated Oxygen Variation that appears in the morning amongst the sleep statistics. If the line is green your blood oxygen is fine, orange indicates there may be a problem. There are also two horizontal lines which show the healthy range. This should give you enough info to know if there’s a cause for concern.

If you wan’t more data, you’ll need to opt for a premium subscription. This lets you view weekly and monthly trends in the new Health Dashboard. Users can see actual % values during sleep, along with insights, nightly averages and graphs.

The subscription currently runs at $9.99 per month or $79.99 per year. There a free 90 day trial for those who have never tried it before.

Fitbit’s SpO2 clock face

Fitbit has recently introduced a clock face that allows users to view their SpO2 from the wrist. You can find it here in the Fitbit App Gallery. As mentioned above, previously those without a premium subscription could only see an Estimated oxygen variation (EOV) graph in the smartphone app.

The watch face allows you to see the actual value in percent terms. Fitbit says the clock face has been downloaded by more than a million people so far, so it might be worth trying out.

How to install the Fitbit SpO2 clock face

To install the watch face, go to the Fitbit app and click on the Today tab. Then tap your profile picture and your device image. This is what you do install any clock face – the procedure is no different. Choose Clock faces and then All clocks. In the search space (magnifying glass icon) type “SpO2 Signature”. When the clock face is found simply choose Select and then Install.

After that go about using your smartwatch as usual. About an hour or so after you wake up in the morning you’ll be able to see your nightly average SpO2 on the device. Values are calculated on a scale that goes up to 100%. Anything above 90% is considered okay, although you are more likely to be in the high 90s. If instead of the value you see a dotted line, then there was a problem in obtaining the readings.

Fitbit’s SpO2 clock face allows you to check blood oxygen levels with ease

It’s worth pointing out, this functionality goes further than the above mentioned EOV readings. These have been available on Fitbit Charge 3, Fitbit Charge 4, Fitbit Ionic and Fitbit Versa series for a while now. The difference is that the new clock face actually spits out estimated blood oxygen saturation levels and range rather than just graphing variations.

Sleep apnea

Sleep apnea is characterized by pauses in breathing or periods of shallow breathing during sleep. These can last from a few seconds to minutes and they happen many times a night. Heart rate and oxygen levels are prime indicators of sleep apnea, a disorder some 22 million Americans suffer from.

Essential reading: Top fitness trackers and health gadgets

The condition can be cumbersome and costly to detect. But tracking blood oxygen levels overnight is a way to detect whether you suffer from it. Fitbit has, however, stopped short of diagnosing any conditions such as sleep apnea. But this may change in the near future.

Now that the SpO2 sensor is here, the company is looking to get FDA approval to diagnose and monitor for sleep apnea.

“Fitbit is continuing to collect clinical data to test and develop FDA-cleared features for sleep apnea,” a Fitbit spokesperson told Gizmodo recently

“They expect to submit for FDA clearance soon and are maintaining a dialogue with the FDA throughout this process.”

What this means is that we may not be too far off from Fitbit gaining permission from the US regulator to monitor for sleep apnea. The company could even be the first to get this approval for a widely available fitness band/smartwatch in the US.

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Ivan Jovin

Ivan has been a tech journalist for over 7 years now, covering all kinds of technology issues. He is the guy who gets to dive deep into the latest wearable tech news.

3 thoughts on “Using the Fitbit SpO2 sensor to track blood oxygen, what you need to know

  • “Actually it is enabled if users are spotting the green light from time to time and Fitbit is using the value for the Sleep Score Beta.”

    No. Red light.

    • Yup, thanks.

  • The sleep score has been released with the new Fitbit App. However, it’s behind a paywall ( new Premium ). It’s described in this article:

    The feature doesn’t use SpO2 ( according to the Community Forum moderators ).

    Does anyone still believe there is going to be any SpO2 monitoring on Fitbit devices? I don’t even believe they have such sensor anymore ( I have never seen “red light” on my Ionic and to be honest – red light means nothing, just a LED ).


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