iOS 18.6.1 restores Blood Oxygen on Apple Watch Series 9, Series 10, and Ultra 2 in the U.S., shifting results to the iPhone Health app instead of the watch.
iOS 18.6.1 is a little but significant update that finally returns the Blood Oxygen capability for Apple Watch Series 9, Series 10, and Ultra 2 users in the United States. After being deactivated owing to a patent dispute, Apple has devised a creative solution to restore it while still releasing bug fixes and preserving consistent performance.
What is iOS 18.6.1
iOS 18.6.1, released on August 14, 2025 with build number 22G90, is a maintenance update that aims to restore a disabled health feature. Along with watchOS 11.6.1, the update reintroduces Blood Oxygen monitoring for Apple Watch devices in the United States that are affected by a trade prohibition.
Key Features and How It Works
- Blood Oxygen Workaround (U.S. only):
- Applies to Apple Watch Series 9, Series 10, and Ultra 2 sold after the U.S. ban.
- The watch still initiates the reading, but the calculation is performed on the iPhone.
- Results are visible only in the Health app under the Respiratory section.
- Users get instructions on the watch like “Recording complete — open Health on iPhone to see results.”
- Bug Fixes:
- Apple lists general bug fixes, though reports mention some users still face Messages and Settings app crashes.
- Apple lists general bug fixes, though reports mention some users still face Messages and Settings app crashes.
- Security Updates:
- No new CVE entries were published, meaning no fresh security patches this time.
- No new CVE entries were published, meaning no fresh security patches this time.
- Performance and Battery Life:
- Similar to iOS 18.6, battery life remains stable and efficient. Overnight drain is minimal, with Geekbench scores showing only slight changes.
- Similar to iOS 18.6, battery life remains stable and efficient. Overnight drain is minimal, with Geekbench scores showing only slight changes.
- Update Size & Compatibility:
- Size: 400–720 MB, depending on device.
- Supported Devices: iPhone XS and later, including SE (2nd/3rd Gen) and all iPhone 16 models.
Why It Matters
Apple was forced to disable Blood Oxygen readings in the U.S. after losing a patent dispute with medical device maker Masimo. This update cleverly restores the feature by moving part of the process off the watch. For U.S. users who lost access, this is a major relief—reinstating one of the Apple Watch’s key health monitoring tools.
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Who Should Update
- Apple Watch U.S. users (Series 9, 10, Ultra 2): You must update if you want Blood Oxygen monitoring back.
- iPhone XS and newer users: Worth updating for stability and bug fixes.
- Non-U.S. Apple Watch users: Your watch already works as before, but updating ensures smoother performance.
Quick Specs Table
| Feature | iOS 18.6.1 Update |
|---|---|
| Release Date | August 14, 2025 |
| Build Number | 22G90 |
| Update Size | 400–720 MB |
| Supported Devices | iPhone XS and newer |
| Watch Feature Restored | Blood Oxygen (U.S. only, Series 9/10/Ultra 2) |
| Security Updates | None published |
| Performance | Stable, minimal battery drain |
Conclusion:
iOS 18.6.1 update is more than just a small patch—it’s Apple’s clever workaround to bring back the Blood Oxygen feature for Apple Watch users in the U.S. After being disabled due to a patent dispute with Masimo, the function now works by recording data on the watch but shifting the processing to the iPhone. The results appear inside the Health app, ensuring compliance with legal restrictions while still giving users access to important health insights.
For most iPhone users, iOS 18.6.1 also ensures stability, smooth performance, and reliable battery life, similar to the earlier iOS 18.6 release. While it doesn’t add new security patches, it fixes system bugs and restores confidence for Apple Watch owners who missed one of the most useful health tracking tools. In short, this update may be small in size, but it delivers a big win for Apple’s ecosystem of health-focused features.