How Accurate Is the Blood Oxygen Level on Apple Watch?

Apple is arguably one of the leading brands when it comes to smartwatches. The apple watch offers some of the best features a smartwatch can offer.

And in recent years, Apple has developed its blood oxygen app to measure the blood oxygen levels of its wearer. But how accurate is the blood oxygen level on the Apple watch? Why is Apple Watch facing so many negative reviews on accuracy?

If these are the questions that are bothering you, then this blog is just for you.

Here, we will go through all the details and information surrounding the Apple watch’s blood oxygen app, how it works, how good is the blood oxygen sensor, how it gathers blood oxygen data, and many more.

1. What Is Apple’s Blood Oxygen App?

As the name suggests, the blood oxygen app is an application function in the Apple Watch (Apple watch series 6 or higher). It monitors the blood oxygen levels of its wearer, and to measure blood oxygen levels, the device utilizes its built-in sensors.

The Apple watch has lights located at the bottom. When you start to use the blood oxygen app, the lights turn on, creating signals that are reflected back towards the watch. The light reflected is then received by the blood oxygen sensor, and the display shows you the result.

Sounds simple, doesn’t it? But then why do so many people complain about the accuracy of Apple Watches in monitoring blood oxygen levels?

This is because the data on blood oxygen saturation isn’t enough to provide an accurate conclusion. Thus making the blood oxygen readings less accurate, to begin with. And users have received a lot of false alarms due to this.

Maybe, for this reason, the Apple Watch isn’t certified by the FDA regarding blood oxygen testing.

That is why the blood oxygen measurements from the Apple watch series are infamous for their inaccuracy. This statement will be clear once we take a look into the difference between blood oxygen measurements between Apple Watch and commercial oximeter devices.

2. Blood Oxygen Measurement: Traditional vs. Apple

If we follow the traditional methods, then going with a pulse oximeter is the best way for blood oxygen reading. They are extremely reliable and provide accurate results without any trouble. That is why pulse oximeters are used in almost every clinical practice related to blood oxygen saturation in the world.

So, how different are they from the Apple watch’s blood oxygen measurement technique? Let’s find out!

2.1 Pulse Oximeter

Pulse Oximeter

A pulse oximeter uses light to get information regarding the blood oxygen level in the body. It utilizes cold light sources like light through back crystal or green LEDs or infrared light to shine through the fingertip to detect the color of the blood. Bright red blood reflects back to the sensor, and others pass through.

The device then does a fast analysis of where oxygen concentration was high and where it was low. And then, it gives you the results regarding the oxygen level in your blood vessels. 

These test results are 100 % accurate and are also certified by FDA. This process of gathering data on blood oxygen is referred to as pulse oximetry.

2.2 Apple Blood Oxygen App

On the other hand, the health app in apple watch series 6 or higher follows a completely different path when it comes to blood oxygen level measurements.

To find out the oxygen saturation, the device utilizes the blood flow in the wrist. Similar to the pulse oximeters, the Apple watch has lights at the back, and when you select, measure blood oxygen from the application. The red and green LEDs of the watch will light up and start the checking process.

During this, the red light will shine at the back of the device. And from here, the process is identical to the pulse oximeter. So, after continuous monitoring for a few seconds, the app will let you know how much oxygen you have in your red blood cells.

The method that the Apple Watch uses to check blood oxygen levels is regarded as ambulatory oximetry.

2.3 What’s the Difference?

As we can see, the main difference here is from where the blood sample is being taken from. In the Apple watch’s case, the data is from blood circulation on the wrists, where there isn’t much natural blood flow, to begin with.

But for the oximeter’s case, we are taking data directly from the fingertips. Here blood circulation is high, and there is also enough room for light to properly reflect back. This is why there isn’t any unsuccessful measurement noticed during pulse oximeter tests, but a lot in Apple watch blood oxygen app.

As there is more blood oxygen data, to begin with, the device gets a lot of information to analyze, and thus the results become more accurate. This is why pulse oximetry has heavy medical use but ambulatory oximetry not so much.

3. Why Apple Watch Blood Oxygen Readings Aren’t Suitable for Regular Use

The reasons why we find the Apple Watch (series 6 and beyond) not suitable to measure blood oxygen for most people are:

3.1 Don’t Have Enough Data

The first issue with the Apple watch blood oxygen app is that it can’t gather enough data, to begin with. There isn’t much blood circulation going on in the wrist area of our body. 

Thus, there isn’t much for the device to work in the first place which makes calculations much more difficult from the beginning.

3.2 Light Doesn’t Completly Shine Through

For calculating the oxygen use, the light needs to shine through the blood first. But as it is located in the wrist area, it is a bit difficult for the light to completely pass through.

This makes the data less secure, and we end up with an inaccurate result, hinting we might have several respiratory diseases and a few lung diseases.

3.3 Complicated & Taxing Analysis Process

While it may seem easy at first, you need to be cautious when taking blood oxygen tests via Apple watch. Wearing the watch properly, especially during the data analysis process, is difficult.

You need to keep your hands extremely still for 15 seconds, otherwise, your result will be inaccurate. Also, letting the light shine through the blood is very important, and not wearing the watch properly will ensure just that.

3.4 Isn’t Suitable for Different Environments

The app can’t measure sudden environment changes and up with messed-up background measurements. For example, if you are in a high altitude or high elevation environment, then results might show you that you are having less or more oxygen in your blood. But, in reality, nothing has changed.

3.5 Requires the Body to Be in Optimal State

In order to have the most accurate result on blood oxygen via the Apple watch, our bodies need to be in optimal condition. This includes the motion of our hands and wrist, body temperature, heart rate, skin perfusion, and a few other conditions.

3.6 Can Mislead People Regarding Lung Disease

Inaccurate blood oxygen results can be very critical for those who want to maintain good health. Healthy adults’ blood oxygen levels should be around 95-100, but many Apple watch users had seen numbers even below 60 when they were completely healthy.

This can mislead people into thinking they might have some serious chronic obstructive pulmonary disease like pulmonary fibrosis or severe chest deformities. However, in most cases, it turns out to be a false alarm. 

Many might buy these devices just to check whether they have skin pigmentation or lung disease, but if they get the wrong data, then what was the point of purchasing them in the first place?

4. So, Is Apple Watch & Its Health App Completely Unreliable?

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Now, you might think that we think the Apple watch and its app are totally unreliable and don’t work at all. No, that’s not true. We just believe that patients presently living with physical respiratory diseases should avoid them to monitor oxygen prescriptions.

Apple watch wears the digital crown for providing high-quality monetization tools for general fitness monitoring. 

Features like heart rate monitor, skin temperature notification, and sleep tracking, are great for wellness purposes. In this category, it is quite unbeatable and offers an acceptable level of results, especially for heart rate monitoring.

But the blood oxygen feature of the apple watch series is not of medical grade. Unlike heart rate calculation where the device uses an optical heart sensor. Here, the sensor isn’t able to perform well enough to take a blood oxygen test that is super accurate.

Sometimes it is able to provide accurate results but at the same time can provide some ridiculous numbers that will shock you out. This might even lead you to think that you are sick with a chronic obstructive pulmonary disease when you actually have no chronic respiratory failure.

So, yes, the apple watch series 6 and above’s blood oxygen app can be highly unreliable and inaccurate at times and is therefore not recommended for medical use.

Nevertheless, the other health-related features and background readings are decently accurate. And maybe in the future, the apple watches will improve on what Series 6 and Series 7 couldn’t and offer accurate results with a balanced level of motion artifacts.