How Does SpO2 Oxygen Sensor Work In Smartwatch: Is It Reliable?

How Does SpO2 Oxygen Sensor Work

We used to get only a Heart-Rate monitoring sensor in most smartwatches but after the COVID-19, now whether it’s a budget smartwatch or premium, we’re also getting a SpO2 sensor.

The biggest question is,

Are SpO2 sensors on smartwatches reliable? how do they work compared to any Oximeter?

How SpO2 Sensor Works in Smartwatch

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Measuring Spo2 Using Smartwatch

When you measure the SpO2 on a smartwatch, it projects LED lights into the skin to measure oxygen levels, the difference between injected light and reflected light is the final result of SpO2 in blood cells.

The smartwatches use photoplethysmography (PPG) sensors to measure the SpO2 percentage as well as the Heart-Rate.

Is SpO2 Sensor Reliable In Smartwatch?

How SPO2 Sesnor works Image01
Measuring Spo2 Using Oximeter

To answer that question, first, you need to know about Oximeter,

When you place your finger in an oximeter, one end of the device emits light using a light source, which then passes through the finger and then hits the sensors at the other end.

This sensor reads the light properties, wavelength, etc, and depending on the measurement calculates the SPO2 level.

In simple words, No SpO2 Sensor in smartwatches are not reliable, still, in the end, it also depends on what kind of smartwatch you’re using,

For example, measuring SpO2 on Apple Watch or Galaxy Watch will be more reliable as they use good quality SpO2 sensors whereas using a SpO2 sensor in a Rs 5000 smartwatch won’t give you an accurate result.

What is SpO2 or Blood Oxygen

Red blood cell
Red Blood Cells

The SpO2 or blood oxygen levels are the percentage of oxygen in the blood. Simply put, it measures how much oxygen your red blood cells carry.

Also, if you’re having symptoms like headache, shortness of breath, coughing, sneezing, bluish color in skin or nails, and more.

In this case, you better visit a nearby hospital because Lower blood oxygen levels can result in Hypoxemia.

According to WHO, a patient with oxygen saturation of 94% or lower needs quick medical attention. And if less than 90%, it’s a clinical emergency.

So what I’m saying is, if your smartwatch is showing SpO2 levels of 90% and you don’t have any symptoms which I mention then there is a chance that, the smartwatch you’re using is unreliable, you better get an oximeter.

These days, oximeters are not that expensive, having only one oximeter at home will help all of your family members.


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When it comes to your health, you should not rely on smartwatches, they’re good but still, they’re not the best.

I hope, this article was helpful but still, if you’re having any doubts or questions then do let me know in the comment box…

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*images: Engineering Semester

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