Apple Restores U.S. Blood Oxygen Feature in iOS 18.6.1

Apple pushed a targeted update on August 14: iOS 18.6.1 (and watchOS 11.6.1 for certain watches) restores a redesigned Blood Oxygen experience for U.S. users with Apple Watch Series 9, Series 10, and Apple Watch Ultra 2.

What changed

The update recreates the Blood Oxygen app experience for eligible U.S. customers, but with an important technical shift: sensor data from the Blood Oxygen app on the Apple Watch is now measured and calculated on the paired iPhone. Results are visible in the Respiratory section of the Health app.

To get it: go to Settings > General > Software Update on your iPhone and tap Update Now. Owners of compatible Apple Watches should install watchOS 11.6.1 to enable the new experience.

Who gets it and why

Apple said the update applies only to U.S. users with the specified watch models. It won’t change watches that still have the original Blood Oxygen feature or devices sold outside the United States. Apple framed the roll-out as a response to a recent U.S. Customs ruling tied to a patent dispute with Masimo that led to an earlier import restriction and the temporary disabling of the feature in January 2024.

Why it matters

This is more than a UI tweak. Moving measurement calculations from wrist to phone changes the device-to-cloud data flow, calibration assumptions, and possibly how results align with prior readings. For users, the change restores a useful health feature; for developers and health platforms, it alters where algorithms run and how raw sensor data is handled.

Immediate steps for users and teams

• Update iPhone to iOS 18.6.1 via Settings > General > Software Update.
• Install watchOS 11.6.1 on Series 9, Series 10, or Ultra 2 to enable the new Blood Oxygen workflow.
• If you rely on historical Blood Oxygen readings, expect possible small measurement differences since calculations now happen on a paired iPhone.

Implications for developers, health providers, and IoT teams

Product and engineering teams should review data provenance, validation logic, and any downstream analytics that use blood oxygen metrics. Shifts in where computations occur can affect latency, battery impact, and privacy boundaries. Clinicians and researchers integrating consumer device data will want to note the change when comparing longitudinal measurements.

For organizations building health features, this moment is a reminder to treat device firmware and OS updates as part of product risk management: small platform changes can cascade into analytics, regulatory filings, or clinical workflows.

How QuarkyByte views this update

At QuarkyByte we treat shifts like this as an operational signal: they reveal dependencies between hardware, OS, and data consumers. Teams should run focused audits to compare pre- and post-update readings, confirm calculation parity, and document any user-facing messaging that explains changes in measurement behavior.

Whether you manage a clinical integration, consumer analytics, or device firmware, this update is a practical case for proactive telemetry validation and regulatory awareness. Expect more platform-driven changes as vendors and regulators interact around health sensor IP and imports.

Bottom line: iOS 18.6.1 brings back a useful health feature for eligible U.S. users, but it also shifts the technical surface area. Teams should update devices, recheck assumptions, and treat the change as part of ongoing device-data governance.