Apple Watch Blood Oxygen Monitoring Returns in US

Apple Watch

In a significant update for developers and health tracking enthusiasts, Apple is reactivating the Blood Oxygen (SpO2) monitoring feature for certain Apple Watch models sold in the U.S.—but with a clever workaround.

What’s Changing

Starting August 14, 2025, Apple is rolling out a redesigned version of the Blood Oxygen feature for Apple Watch Series 9, Series 10, and Ultra 2 models affected by a 2024 import ban. The feature had been disabled due to a legal dispute over patent infringement with medical device maker Masimo.

How It Works Now

To re-enable Blood Oxygen monitoring, users must install iOS 18.6.1 on their iPhone and watchOS 11.6.1 on their Apple Watch.
After updating, the Apple Watch collects SpO2 sensor data, but all measurement calculations are processed on the paired iPhone. Results are then accessible in the Health app’s Respiratory section.
This redesign elegantly circumvents Apple’s ongoing legal challenges under U.S. Customs approval.

Who’s Affected—and Who Isn’t

Newly affected models: Units sold after January 17, 2024, with serial numbers ending in LW/A, had the Blood Oxygen feature disabled at purchase but will now regain it via the update.
Unaffected units: Apple Watches bought before the ban or outside the U.S. continue to support the original Blood Oxygen feature as before.

Wider Implications & Context

The legal throttling began after Masimo alleged that Apple’s pulse oximetry tech infringed its patents, prompting the U.S. International Trade Commission (ITC) to enforce an import ban on watches with the SpO2 feature starting in late 2023.
Apple has appealed the ruling and introduced this software workaround to maintain functionality while respecting the legal constraints.

Quick Summary Table

Device Model	Pre-ban Units (pre-Jan 18 2024)	Post-ban Units (serial LW/A)
Series 9 / Series 10 / Ultra 2	Full SpO2 support on watch	SpO2 via iPhone after OS update
Purchased outside the U.S.	Full SpO2 support	N/A (not impacted)

Whether you’re a developer working on health-focused apps or a C# Corner reader interested in how system constraints shape software solutions, this move from Apple showcases how adaptive engineering—in this case, shifting computations to another device—can preserve functionality in the face of legal hurdles.