ADAM ENGST 14 August 2025

A U.S. Customs ruling has allowed Apple to restore blood oxygen readings for U.S. Apple Watch buyers for whom the feature was disabled in early 2024. For these users, the redesigned approach works by measuring on the Apple Watch, processing data on the iPhone, and displaying results in the Health app.

After medical device maker Masimo’s patent infringement complaint regarding the blood oxygen sensor on the Apple Watch, Apple was compelled in late 2023 to cease selling the Apple Watch Series 9 and Apple Watch Ultra 2 in the U.S. (see “Apple to Stop Selling Two Apple Watch Models in the US Due to Import Ban,” 18 December 2023). Soon after, Apple negotiated a workaround that allowed it to resume sales by throwing a software switch that disabled the blood oxygen sensor for new Apple Watch buyers in the U.S. (see “Apple Disables Blood Oxygen App in New Apple Watches,” 18 January 2024). Hardware remained unchanged, and models with blood oxygen sensors sold before the ban continued to have access to the watchOS Blood Oxygen app. Sales of Apple Watch models in other countries were also unaffected.

Apple has been fighting the legal case all this time and seems either unwilling or unable to settle with Masimo. However, a recent U.S. Customs ruling has enabled Apple to make a technical compromise. Apple says:

Users with these models in the U.S. who currently do not have the Blood Oxygen feature will have access to the redesigned Blood Oxygen feature by updating their paired iPhone to iOS 18.6.1 and their Apple Watch to watchOS 11.6.1. Following this update, sensor data from the Blood Oxygen app on Apple Watch will be measured and calculated on the paired iPhone, and results can be viewed in the Respiratory section of the Health app.

This new iPhone-focused experience won’t apply to earlier Apple Watch units that still have the Blood Oxygen app, nor to units purchased outside the United States.

It’s possible that Apple hasn’t been interested in settling with Masimo because the feature isn’t that important for everyday wellness. As Rich Mogull wrote in “The Paramedic’s Guide to Blood Oxygen and the Apple Watch Series 6” (22 October 2020), those with known lung disease can use it to determine if their condition is worsening, and people who suspect respiratory issues like pneumonia or COVID-19 can use it to decide if they need immediate help. Useful, but not something most people would use regularly.

Rich also said it could theoretically help identify sleep apnea, but he felt the data collected during sleep wasn’t reliable enough. Last year, Apple introduced sleep apnea notifications in watchOS 11, saying that it uses the accelerometer to detect interruptions in normal respiratory patterns, a technique Apple validated in a clinical study.

In short, if you have an Apple Watch Series 9, Apple Watch Series 10, or Apple Watch Ultra 2 on which the blood oxygen sensor is disabled, update to iOS 18.6.1 via Software Update and to watchOS 11.6.1 through the Watch app. After updating, you can view blood oxygen data on your iPhone in Health > Browse > Respiratory > Blood Oxygen. Apple doesn’t call out any other changes or security fixes in these updates, so if your Apple Watch isn’t affected or you’re not interested in tracking blood oxygen, you can ignore these updates.