So you can measure the level of oxygen in the blood with your Apple Watch — 2022

Apple Watches already allow blood oxygen saturation measurement with a simple touch. The problem is that specific conditions have to be met for a measurement to come out as close to reality as possible. In this article we tell you everything you need to know about this new health function.

Requirements to perform the measurement

In order to use this function, a series of requirements must be met. For example, that the application is available in the country where you live, something that can be consulted in the initial configuration processes. In addition, you have to have a compatible Apple Watch since not all of them integrate the necessary sensors. Specifically, the compatible models are the following:

  • Apple Watch Series 6 de 40 o 44 mm.
  • Apple Watch Series 7 de 41 o 45 mm.

In addition, in any case, you must have the most recent version of watchOS installed as well as an iPhone 6s or higher with the latest version of iOS available. To this is added the requirement of being over 18 years old to be able to use the necessary application, since the algorithm has not been tested on minors.



Initial setup

When you are configuring your Apple Watch with the sensors to be able to measure oxygen saturation, a window will appear explaining how it works. This is where you can click on 'Activate' to download the application to do so. In the event that you have not activated it in the initial configuration, you can simply follow these steps:

  • Open the 'Health' app on your iPhone with the paired Apple Watch.
  • Navigate to the 'Browse' tab.
  • Follow the path Breathing > Blood Oxygen > Set Blood Oxygen.

set up blood oxygen Apple Watch

At this time you will be asked to make the activation configuration so that the data can be collected. In the event that the application does not appear either, you can simply go to the App Store and download the application 'Oxígeno en Sangre' to force you to have it. Obviously this is only possible if you have a watch compatible with this functionality.

Take the measurement with the Apple Watch

Once you have made sure that you have made the configuration, fulfilling all the requirements in any case, it is time to carry out the measurement. For this you must make sure that the Apple Watch is tight to the wrist but in no case tight. In addition, the fist must be open and the hand relaxed so that the result is as successful as possible as well as faithful. Once you have taken these indications, you simply have to follow the following steps to perform the measurement:

  • Open the 'Blood Oxygen' application on the Apple Watch.
  • Do not move and keep your wrist in a horizontal position, better supported on a surface such as a table.
  • Click on 'Start' and wait 15 seconds while the measurement is made.
  • Once this measurement has elapsed you will have access to the result.

measure blood oxygen apple watch

The problem that arises is that an interpretation of the results obtained in the measurement is not made. It does not happen as in the case of ECGs that an assessment is made by the algorithm of whether it is normal or not. That is why these results must always be evaluated with medical knowledge, although it must always be taken into account that this is not a medical device. If you have any type of symptom you have to go to a health center to have a measurement done with an oximeter.

It should be noted that the application performs measurements in the background as long as you have it active in the Apple Watch application. The watch intelligently detects when you are not moving to take the measurement, ideal for when you are sleeping to detect certain pathologies. The problem is that the red light used to measure oxygen saturation can end up annoying or distracting.

Consult historical data

All the data that is obtained from the measurements that are made are stored for consultation in the Health application. In this way you will be able to consult in a graph the evolution that the saturation has had over time. This is ideal above all to be able to check if this has had something to do with a pathological condition that you have suffered. To perform this query you simply have to follow the following steps:

  • Open the Health app.
  • At the bottom, click on 'Explore'.
  • Tap Breathing > Blood Oxygen.

blood oxygen Health iPhone

Something extremely interesting that is integrated into this information interface is the possibility of filtering the data obtained by situations. You can always choose whether you want to see the measurements that have been taken while you sleep and even at high altitudes.

Common Oxygen Meter Failures

Oxygen saturation measurement is not perfect on the Apple Watch. It must be taken into account that we are not dealing with a medical section such as an oximeter, despite the fact that it includes very similar sensors, in the end we are not dealing with the same device. On many occasions, a failed result can occur in the measurement, which may be because you have moved or the strap is not properly fastened so that it works properly.

oxygen measurement failed apple watch

But there are other conditions that can affect having a successful measurement. For example, changes in skin color temporarily or permanently can cause the measurement to be inconclusive. This occurs mainly with tattoos that are on the wrist and that can cause the light from the sensor to be blocked, making light difficult, since different photodiodes are used to measure the light that is refracted. Skin perfusion can also vary from person to person, that is, the amount of blood that is flowing through the skin. As a defense measure, the body can reduce skin perfusion when hypothermic conditions occur, making measurements difficult.

technical operation

From the Apple Watch Series 6 onwards, heart rate sensors are used to project an infrared light towards the wrist. The light that is reflected at that moment can be read by photodiodes so that it can be interpreted. Thanks to the algorithm that is included in the software, all the measurements that have been taken can be interpreted to give a result as a percentage. It must be taken into account that the color of the blood is an indication of the oxygen saturation. In the event that you have very oxygenated blood, the color is intense red but it darkens as soon as the saturation is reduced.

failed oxygen measurement scheme apple watch

Usefulness of measuring oxygen saturation

In order to understand the usefulness of this function, you need to know what oxygen saturation is. In short, it is the amount of oxygen in the blood associated with red blood cells, and as long as it is at optimal values, it is indicative that the cells are receiving enough oxygen to carry out their cellular processes. Although it is reminded on many occasions that this function has not been designed for medical use or self-diagnosis, it can give indications to create a pathological picture. Obviously, if the device gives a result of less than 85% and you have some type of respiratory or vertiginous symptomatology, it is advisable to go to a medical center. Independently with a punctual result of a low oxygen saturation it is not indicative of disease. It must be understood that this result cannot be taken as the absolute truth in any case, and less so if it has been punctual, since, as we have previously commented, numerous errors can occur in the measurement.

Likewise, this function is recommended for those people who suffer from some important ailment or who are elderly. In no case does it detect infectious pathologies such as COVID-19, but rather it can report a symptom that can fit with numerous diseases such as asthma, bronchitis, COPD, pulmonary edema and endless pathologies. Obviously we repeat that this may be a symptom that should be interpreted with a complete medical history.

How to treat the data obtained

In the event that the watch obtains abnormally low saturation data, especially in the morning, it is interesting that you try to corroborate it with a pulse oximeter. These data, as we have previously commented, are not 100% reliable. They always have to be evaluated by a medical team and not act independently in these cases.