Introduction
The blood oxygen (SpO₂) monitor has been one of the most valued health tools on the Apple Watch, giving users quick and noninvasive insights into their wellness and respiratory performance. Introduced in 2020 with the Apple Watch Series 6, it became especially popular among athletes, hikers, and people monitoring conditions like sleep apnea or other breathing-related issues.
In early 2024, U.S. buyers were surprised to find the feature missing from the Apple Watch Series 9 and Ultra 2. This change wasn’t due to a design choice but the result of a high-profile patent dispute with medical technology company Masimo, which temporarily forced Apple to remove the SpO₂ sensor’s functionality in the U.S.
Now, in August 2025, the blood oxygen feature is making a return to these models though with limitations. Apple has implemented a workaround that allows U.S. users to access readings again, but the experience isn’t identical to what international customers or earlier Apple Watch owners enjoy. This partial restoration marks a significant update for health-focused users while also highlighting how legal battles can shape the technology we use.
A Feature Removed, Then Slowly Restored
The Apple Watch’s blood oxygen sensor measures the percentage of oxygen in your bloodstream, a key metric for assessing overall wellness. It’s useful for tracking altitude acclimatization, identifying early signs of respiratory issues, and supporting fitness recovery monitoring.
In late 2023, the U.S. International Trade Commission (ITC) ruled in favor of medical technology company Masimo, which alleged that Apple’s pulse oximetry technology infringed on its patents. This decision led to an import ban on certain Apple Watch models containing the disputed feature.
To comply, Apple began disabling the SpO₂ functionality on newly imported U.S. Apple Watch Series 9 and Ultra 2 models starting January 17, 2024. Devices sold outside the U.S. or purchased before that date remained unaffected and continued to offer full readings. For nearly a year, many U.S. buyers were left without one of the watch’s most recognizable health features until Apple introduced a modified version of the tool in mid-2025, allowing partial functionality without violating the ITC ruling.
The Workaround: How Apple Brought It Back
On August 14, 2025, Apple reintroduced blood oxygen tracking for affected U.S. Apple Watch models, but the feature now works differently to comply with the ITC ruling. The changes ensure that Apple can legally offer SpO₂ monitoring without infringing on Masimo’s patents.
Here’s what’s different:
- Software Update Required: To restore access, users must install watchOS 11.6.1 on their Apple Watch and iOS 18.6.1 on the paired iPhone. Without these updates, the feature remains unavailable.
- Processing Happens on the iPhone: While the Apple Watch hardware still captures raw SpO₂ data, the watch no longer processes or displays results directly. Instead, all calculations now occur within the Health app on the paired iPhone.
- Limited Availability: The workaround only applies to Apple Watch Series 9, Series 10, and Ultra 2 models sold in the U.S. after January 17, 2024, with serial numbers ending in “LW/A.” Watches purchased before the ban or imported from outside the U.S. continue to function normally without these changes.
- No Instant On-Wrist Readings: Users can no longer check SpO₂ readings directly on the watch face. Instead, results appear in the Respiratory section of the iPhone’s Health app.
Why Apple Had to Make This Change
Apple’s workaround is both a technical and legal solution. By moving the computational processing of SpO₂ readings from the watch to the paired iPhone, the company avoids infringing the patents cited in the ITC ruling.
This adjustment satisfies the ITC’s requirements, and U.S. Customs has confirmed that the new architecture is compliant. As a result, Apple can once again sell affected Apple Watch models with blood oxygen tracking re-enabled though the feature no longer operates exactly as it did originally, with on-wrist readings now replaced by iPhone-based analysis.
What This Means for Users
| What’s Back | What’s Different |
|---|---|
| Blood oxygen tracking on Series 9, 10, and Ultra 2 sold after Jan 2024 | Readings only appear on iPhone, not directly on the Watch |
| Function restored via software update | Applies only to models with LW/A serial numbers |
| Legal compliance with U.S. import rules | Still unavailable if you skip the update |
For users who value convenience, the change is a compromise. You get the health insights back, but lose the instant, on-the-go wrist display that made the feature so seamless.
The Ongoing Legal Battle
Apple’s appeal of the ITC ruling is still underway, and Masimo’s patents are not set to expire until August 2028. This means the full restoration of on-watch SpO₂ processing is unlikely unless Apple either succeeds in court or reaches a licensing agreement with Masimo.
In the meantime, the current “iPhone-only” workaround represents the most Apple can legally offer to U.S. customers, allowing access to blood oxygen readings while staying within the limits of the ITC order.
Conclusion
The reintroduction of blood oxygen tracking on the Apple Watch in the U.S. is a welcome development for health-conscious users, particularly those who purchased a Series 9, Series 10, or Ultra 2 after January 2024. While the workaround requiring readings to be viewed on the iPhone rather than directly on the wrist is less convenient than the original setup, it restores a vital health-monitoring feature that was unavailable for nearly a year.
This solution represents a temporary but important step in Apple’s ongoing legal battle with Masimo. Ultimately, the resolution of this dispute could shape the future of health sensors on Apple’s wearable devices, influencing how users access and track critical wellness data in the years to come.
FAQ: Apple Watch Blood Oxygen (SpO₂) Tracking in the U.S.
- The SpO₂ monitor measures the percentage of oxygen in your blood. It provides noninvasive insights into overall wellness, supports fitness recovery, helps track altitude acclimatization, and can alert users to potential respiratory issues.
- In late 2023, the U.S. International Trade Commission (ITC) ruled in favor of Masimo, claiming Apple’s pulse oximetry technology infringed on its patents. To comply, Apple disabled the feature on new U.S. imports of Series 9 and Ultra 2 models starting January 17, 2024.
- No. Watches purchased outside the U.S. or sold in the U.S. before January 17, 2024, continue to offer full SpO₂ functionality. The workaround applies only to Series 9, Series 10, and Ultra 2 models sold in the U.S. after that date with serial numbers ending in “LW/A.”
- As of August 14, 2025, Apple reintroduced blood oxygen tracking via a software workaround. Users must update to watchOS 11.6.1 and iOS 18.6.1. While the watch still captures raw SpO₂ data, all processing now happens on the iPhone’s Health app.
- No. Instant on-wrist readings are no longer available. SpO₂ results now appear in the Respiratory section of the iPhone Health app.
- Shifting SpO₂ computation to the iPhone allows Apple to comply with the ITC ruling, avoiding patent infringement while still giving users access to oxygen level data.
- Not necessarily. Apple is appealing the ITC ruling, and Masimo’s patents won’t expire until August 2028. A full return to on-watch processing may be possible if Apple wins the appeal or reaches a licensing agreement.
- The workaround restores access to an important health feature, but it’s less convenient than the original wrist-based measurements. Users can still track their blood oxygen levels, but only via their iPhone.
- No. Apple Watch models sold outside the U.S. or prior to the January 2024 import ban retain full on-watch blood oxygen functionality.
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