If you hadn’t already heard of SpO2, it’s likely that you heard the term during the pandemic. COVID-19 can impact blood oxygen by lowering it to an abnormal level. Unfortunately, in some COVID-19 cases patients show no signs of low blood oxygen. This led to the use of pulse oximeters to monitor blood oxygen levels from home during the pandemic.

What is blood oxygen level?

Blood oxygen is the amount of oxygen found circulating in your blood. Oxygen is carried by red blood cells and is measured as a percentage referred to as SpO2 or oxygen saturation. SpO2 is the percentage of oxygen-carrying red blood cells compared to those not carrying oxygen.

But where does this oxygen come from? The oxygen carried by red blood cells enters your body with each inhale and is transported from the air, to your lungs, and then to red blood cells. Red blood cells have the crucial job of transporting oxygen throughout the body. Think of red blood cells as the delivery truck carrying a package (oxygen) to its destination. Red blood cells transport oxygen to cells throughout the body enabling them to perform their duties.

Measuring SpO2

Blood oxygen is measured directly by quantifying the amount of oxygen gas in a blood sample. However, blood oxygen can be estimated noninvasively with pulse oximetry. A pulse oximeter measures SpO2 without drawing blood by using red and infrared light to detect how much oxygen is in the blood. This is completely painless and is typically done with a finger or ear clip. Pulse oximeters give SpO2 readings within 2-4% of your actual blood saturation level making them a quick and noninvasive estimate for blood oxygen.

In clinical practice, pulse oximeters are typically used to monitor patients in the emergency room, before, during, and after surgery, check lung function, and assess patients with sleep apnea.

It is important to note that research shows that pulse oximetry might not measure blood oxygen for all skin colors accurately. One study found that black patients had three times more missed incidents of hypoxemia (abnormally low blood oxygen levels) than white patients using pulse oximetry.

Measuring SpO2 with a Fitness Tracker

Pulse oxygen is also a useful measurement outside of the clinical setting. By integrating SpO2 measurement into wearable technology, SpO2 can be measured without a specific pulse oximetry device. Companies like Oura, whose rings capture SpO2 during users’ sleep, attest to the utility of SpO2 claiming that it is “a useful index of overall health, as well as indicated possible disturbances in your breathing during the night.” There is research to support this claim showing that pulse oximetry has the potential to diagnose obstructive sleep apnea. However, commercially-available wearables are not yet approved for diagnosing conditions. Their metrics should be used as the first step in assessing and you should follow up with a doctor with any questions.

Normal SpO2

A normal SpO2 is between 95-100%. If while using a pulse oximeter or wearable you see your SpO2 drop below 94%, you should be sure that you are using the device correctly. If repeat measurements are below 94%, you should contact a provider and seek medical attention.

Low SpO2

Your SpO2 may be considered low if it is below 95%. However, keep in mind that pulse oximeters usually have a 2-4% margin of error from your true blood oxygen saturation level.

Conditions like sleep apnea, asthma, other lung diseases, high elevation, or other illnesses can cause a low SpO2. SpO2 can also be lowered by breathing disturbances like congestion.

How to Increase SpO2

Blood oxygen levels can be increased by:

  • Breathing in fresh air that has a high oxygen content

  • Not smoking (smoking decreases the lungs’ ability to take in oxygen)

  • Using breathing exercises to improve lung capacity

Some systemic causes (such as lung problems) of low spO2 may not be correctable by these methods.

What brands and devices have pulse ox?

Apple: Watch Ultra and Watch 8

Coros: Apex 2 Pro, Apex 2, Vertix 2

Fitbit: Sense 2, Versa 4, Charge 5, Versa 2, Inspire 3, Luxe

Garmin: Enduro 2, Enduro, Fenix 7, MARQ, Epix, Descent G1, Quatix 7, Instinct 2, Forerunner 955, Forerunner 945, Forerunner 745, Forerunner 255, Forerunner 245, Vivoactive 4, Vivomove, Vivosmart 5, Vivosmart 4, Venu 2, Venu Sq, Approach S62, and Lily

Oura Ring: Gen 3

Suunto: 9 Peak Pro and 9 Peak

Whoop: Whoop 4

Withings: Scan Watch Horizon and Scan Watch

You can find these fitness trackers on the products page or complete the Takeoff quiz to receive personalized recommendations.

This is for informational purposes only and should not be considered medical advice. Go to the emergency room if you are experiencing a life-threatening medical emergency.

Disclaimer: Takeoff Health may make a small commission from some of the links above.


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