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What is SpO2?

If your smartwatch is capable of measuring your SpO2, you may be wondering what that is and why it’s important. This article explains what you need to know.

When you’re considering what smartwatch or fitness tracker to buy, you may wonder what each of the metrics boasted by these devices actually means for you when you’re reviewing your health and wellness statistics.

SpO2 is one of those measurements that tends to feature in many of the best smartwatches, and this article will explain just what it means for you and your health.

What is SpO2?

The abbreviation SpO2 stands for peripheral oxygen saturation (with “O2” being the chemical formula for oxygen, “S” representing saturation, and “p” representing peripheral).

Oxygen saturation measures “the percentage of haemoglobin binding sites in the bloodstream occupied by oxygen.” Haemoglobin is the oxygen-carrying molecule that’s present in red blood cells, so this metric shows how much oxygen is being carried in your bloodstream out of the potential maximum.

The sensor on your smartwatch can only measure the peripheral blood oxygen saturation levels, at your wrist, but other medical measuring devices are capable of measuring arterial or venous oxygen saturation.

How is SpO2 measured?

SpO2 is measured through a process called pulse oximetry. This is done by shining infrared light through the body area in question (such as a wrist, for your smartwatch) and then measuring the change in absorbed light, since the colour of blood is affected by its oxygen saturation.

Huawei Watch 3 showing the fitness tracker and SpO2 sensor
Image Credit (Trusted Reviews)

The above picture shows the Huawei Watch 3 measuring the user’s SpO2 levels with its pulse oximeter function.

Why is SpO2 important?

Now you know what SpO2 is, you might be wondering what relevance it has to your health. The oxygenation of your blood is vitally important because it allows your cells to create energy through respiration, with with it can then power all of your essential bodily functions.

The NHS advises that you should ask for medical help if your SpO2 number stays at 92% or less.

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