watchOS 11.6.1 brings back Apple Watch's blood oxygen monitoring feature

Apple removed the blood oxygen monitoring feature from its Apple Watch models for US users due to a lawsuit, but it has since been redesigned to bring it back.

An update on Blood Oxygen for Apple Watch in the US - Apple
https://www.apple.com/newsroom/2025/08/an-update-on-blood-oxygen-for-apple-watch-in-the-us/

Apple launching 'redesigned Blood Oxygen feature' on Apple Watch in the US today - 9to5Mac
https://9to5mac.com/2025/08/14/apple-watch-blood-oxygen-feature-returning-in-the-us-today/

Apple Watch blood oxygen workaround arrives just in time - 9to5Mac
https://9to5mac.com/2025/08/14/apple-watch-series-11-ultra-3-blood-oxygen/

The Apple Watch Series 6 , released by Apple in September 2020, is now capable of measuring blood oxygen levels.

Summary of how to use the 'Blood Oxygen Wellness App' that can measure blood oxygen levels with 'Apple Watch Series 6' - GIGAZINE

However, in June 2021, medical device manufacturer Masimo filed a lawsuit with the US International Trade Commission, alleging that the blood oxygen wellness feature included in the Apple Watch Series 6, released in 2020, infringes on its patent for a blood oxygen saturation measurement mechanism.

The US International Trade Commission has ruled that the Apple Watch's blood oxygen monitoring feature infringes on a patent from medical device manufacturer Masimo.

As a result of this lawsuit, Apple was banned from selling Apple Watches with blood oxygen monitoring in the US, and was forced to discontinue sales of the Apple Watch Ultra 2 and Apple Watch Series 9 in the US.

Apple halts sales of Apple Watch Series 9 and Ultra 2 over blood oxygen sensor patent dispute - GIGAZINE

In response, Apple began selling the Apple Watch Series 9 and Apple Watch Ultra 2 in the US without the blood oxygen monitoring feature. Apple released the Apple Watch Series 10 in September 2024, but this model was also sold in the US without the blood oxygen monitoring feature.

However, Apple announced that it will release a 'redesigned blood oxygen monitoring feature' for US Apple Watch users in iOS 18.6.1 and watchOS 11.6.1, released on August 14, 2025. This update will also be available for US Apple Watch Series 9, Series 10, and Ultra 2 models, which did not previously have the blood oxygen monitoring feature.

After updating to iOS 18.6.1 and watchOS 11.6.1, your Apple Watch will download wireless assets for the new Blood Oxygen Monitoring feature. 9to5Mac points out that the download may take up to 24 hours. To start the download, you'll need to open the ECG app on your Apple Watch or the Health app on your iPhone.

The 'redesigned blood oxygen monitoring feature' now supports background blood oxygen monitoring. Apple explains that 'older Apple Watch models with the original blood oxygen monitoring feature and Apple Watch models purchased outside the US are not affected by this update.'

An Apple spokesperson told 9to5Mac in a statement, 'Apple will introduce a redesigned blood oxygen feature to some Apple Watch users in the US through a software update for iPhone and Apple Watch later today. With this update, Apple Watch's Blood Oxygen app sensor data will be measured and calculated on the paired iPhone, and results will be available in the Health app. This update will be available to Apple Watch Series 9, Apple Watch Series 10, and Apple Watch Ultra 2 users in the US who do not have the legacy blood oxygen feature.'