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Apple Watch Blood Oxygen Returns: How Apple Outsmarted a $634M Patent Battle
By [Author Name] | March 27, 2026
Summary Box
What Happened: Apple has successfully reintroduced blood oxygen (SpO2) monitoring to U.S. Apple Watch models after a redesigned version was approved by U.S. Customs and Border Protection in August 2025 .
Why It Matters: The feature had been disabled for over a year due to a bitter patent dispute with medical technology company Masimo, which resulted in a $634 million jury verdict against Apple in November 2025 .
Key Technical Change: Unlike the original version, the redesigned feature processes data on the paired iPhone rather than the watch itself. Results are viewed exclusively in the Health app on the iPhone, not on the watch face .
Latest Legal Update: In March 2026, a U.S. International Trade Commission judge ruled that Apple's redesigned Apple Watches do not infringe Masimo's patents, clearing the way for continued sales .
Introduction: The Feature That Refused to Die
For more than a year, a bitter patent war between Apple and a little-known medical technology company named Masimo left a gaping hole in the Apple Watch's celebrated health feature set. The blood oxygen sensor—first introduced with great fanfare on the Series 6 in 2020—was quietly disabled on new U.S. models, its fate hanging in the balance of a complex legal battle that spanned trade commissions, federal courts, and even U.S. Customs .
But in a move that showcases Apple's characteristic blend of technical ingenuity and legal tenacity, the blood oxygen feature is back. And it's not simply a restoration of what was lost—it's a reimagined version that sidesteps patent claims while preserving the underlying health-tracking capability that millions of users value .
This article explores how Apple brought blood oxygen monitoring back from the dead, what changed in the process, and what it means for Apple Watch users today.
The Legal Minefield: How We Got Here
The Masimo Patent Dispute
The conflict between Apple and Masimo dates back years. The Irvine, California-based medical technology company accused Apple of poaching its employees and stealing its pulse oximetry innovations—technology used to determine oxygen levels in the blood . Masimo alleged that Apple used these stolen trade secrets to develop the blood oxygen sensor that debuted on the Apple Watch Series 6.
The legal fight intensified in 2023 when the U.S. International Trade Commission (ITC) issued an import ban on Apple Watch Series 9 and Ultra 2 models, finding that they infringed Masimo's patent rights . Apple was forced to halt sales of these models in the U.S. just days before Christmas—a significant blow to the company's most important product category.
The First Workaround: Disabling the Feature
Apple's initial response was pragmatic: it removed the blood oxygen feature entirely from new Apple Watch units sold in the U.S. The hardware remained unchanged, but a software switch disabled the Blood Oxygen app for new buyers . This allowed Apple to resume selling the watches, but at the cost of disabling a marquee health feature.
For customers who purchased watches before the ban, the feature continued working normally. International sales were unaffected . This created a peculiar two-tier system where identical hardware behaved differently depending on when and where it was purchased.
Masimo's Legal Victory—And Apple's Countermove
The patent dispute took another dramatic turn in November 2025 when a California federal jury awarded Masimo $634 million in a patent infringement and trade-secret theft trial . Apple has stated its intention to appeal the verdict, signaling that this legal saga is far from over.
But behind the scenes, Apple was already developing a more permanent solution: a redesigned blood oxygen feature that would allow it to restore the capability without infringing Masimo's patents.
The Redesign: How Apple Brought Blood Oxygen Back
Technical Changes: From Watch to iPhone
The redesigned blood oxygen feature represents a clever technical workaround. In the original implementation, the Apple Watch's sensors captured the data, processed it, and displayed results directly on the watch face. This integration—sensing, calculating, and displaying on a single device—was central to Masimo's patent claims .
Apple's new approach separates these functions:
Sensing: The Apple Watch's built-in sensors still capture raw blood oxygen data using the same LED clusters and photodiodes .
Processing: All calculations and analysis are now handled by the paired iPhone, not the watch itself .
Display: Results are viewable exclusively in the Respiratory section of the Health app on the iPhone. The watch no longer shows SpO2 readings directly .
This architectural change was enough to satisfy U.S. Customs and Border Protection, which approved the redesigned feature in August 2025 .
Software Requirements
To access the restored feature, users need to update their devices:
After updating, the blood oxygen functionality becomes available on compatible Apple Watch models that previously had the feature disabled.
Which Models Are Supported?
The redesigned blood oxygen feature is available on:
Apple Watch Series 9
Apple Watch Series 10
Apple Watch Ultra 2
For users with Series 6, 7, 8, or the original Ultra that were purchased before the ban, the original blood oxygen feature continues to work without changes .
Note: Apple Watch SE models have never included blood oxygen monitoring capabilities .
How It Works: Using the Restored Blood Oxygen Feature
The Technology Behind the Sensor
The Apple Watch's blood oxygen sensor is a marvel of miniaturization. It uses four LED clusters (green, red, and infrared) and four photodiodes integrated into the back of the watch case . The LEDs shine light onto the blood vessels in the user's wrist, while the photodiodes measure how much light is reflected back.
Because oxygenated and deoxygenated blood absorb light differently, the sensor can calculate the percentage of oxygen in the blood—known as SpO2 (peripheral capillary oxygen saturation) .
Taking a Measurement
With the redesigned feature, the measurement process begins on the watch but concludes on the iPhone:
Open the Blood Oxygen app on the Apple Watch (icon: white circle with red and blue curved lines) .
Ensure the watch is snug but comfortable on your wrist. The band should be secure without being too tight .
Rest your wrist on a flat surface, palm down. Staying still is crucial for accurate readings .
After the measurement, the watch sends an alert to your iPhone. Open the Health app to view your reading .
Viewing Your Data
All blood oxygen data lives in the iPhone Health app:
View readings across different time periods: day, week, month, six months, or year .
For quick access, add the Blood Oxygen card to your Health app summary .
Background Readings
The Apple Watch can also take periodic background readings throughout the day and while you sleep, providing a comprehensive picture of your blood oxygen levels over time . Users can control when background measurements occur:
In Sleep Focus: Disable to prevent the red light from disrupting sleep
In Theater Mode: Disable to avoid distractions in dark environments
What's a Normal Reading?
For most healthy adults, a normal blood oxygen level falls between 95% and 100% . Consistent readings below 90% may indicate an underlying condition and warrant medical attention.
It's important to note that blood oxygen levels can vary based on factors like:
Altitude (readings may be lower at high elevations)
Recent physical activity
Proper watch placement and fit
A Word on Medical Accuracy
Apple includes a clear disclaimer with the Blood Oxygen feature: measurements "are not intended for medical use, including self-diagnosis or consultation with a doctor, and are only designed for general fitness and wellness purposes" .
The feature is best used as a general health indicator rather than a diagnostic tool. Consistently low readings should prompt a conversation with a healthcare provider, not self-treatment.
The Latest Legal Developments (March 2026)
Just as this article was being prepared, significant legal developments occurred that could shape the future of Apple Watch blood oxygen monitoring.
ITC Preliminary Ruling: Apple Prevails
On March 18, 2026, Administrative Law Judge Monica Bhattacharyya at the U.S. International Trade Commission issued an enforcement initial determination finding that Apple's redesigned Apple Watches do not infringe the asserted claims of two Masimo patents (U.S. Patent Nos. 10,912,502 and 10,945,648) .
The judge also determined that Apple does not induce infringement when the redesigned watches are used with an iPhone . This ruling, if ratified by the full ITC, could permanently lift the import ban that has hung over Apple Watch sales since 2023.
Federal Circuit Affirms Original Ban
In a separate development on the same day, a three-judge panel of the U.S. Court of Appeals for the Federal Circuit affirmed the ITC's original 2023 ruling that Apple had infringed Masimo's patents . The court found "no error in the Commission's domestic industry determination, its validity rulings, or its infringement findings" .
Apple responded by stating it was "pleased with" the ITC judge's findings regarding the redesigned watches but disagrees with the Federal Circuit's decision and is "evaluating all avenues for further review" .
What This Means Going Forward
The conflicting rulings create an interesting legal landscape:
Good news: The ITC judge's preliminary ruling suggests Apple's redesign successfully navigates Masimo's patent claims. The full ITC is expected to make a final decision on whether to ratify this finding .
Ongoing uncertainty: The Federal Circuit's affirmation of the original infringement finding means Apple still faces legal exposure for earlier implementations. The $634 million jury verdict from November 2025 remains pending appeal .
For consumers, the practical impact is that blood oxygen monitoring remains available on redesigned Apple Watch models, and the legal path to keeping it that way appears increasingly secure.
What This Means for Apple Watch Users
If You're Buying a New Apple Watch Today
New Apple Watch Series 9, Series 10, and Ultra 2 units sold in the United States now come with the redesigned blood oxygen feature enabled out of the box—provided they have been updated to the latest software . The feature functions as described above, with processing handled by the iPhone.
If You Own an Older Apple Watch
Series 6, 7, 8, Ultra (original): If purchased before the ban took full effect in January 2024, your original blood oxygen feature continues working exactly as it always did. No changes required .
Series 9, Series 10, Ultra 2 (purchased during the ban): If you bought one of these models between January 2024 and August 2025 when the feature was disabled, updating to iOS 18.6.1 and watchOS 11.6.1 will restore blood oxygen functionality using the redesigned iPhone-based approach .
International Users
If you're outside the United States, the patent dispute never affected your Apple Watch. Blood oxygen monitoring continues to work as originally designed, with measurements and display handled directly on the watch .
Expert Analysis: Why This Matters Beyond the Feature Itself
Apple's Playbook: Redesign Rather Than Settle
The blood oxygen saga reveals a recurring pattern in Apple's approach to patent disputes: rather than pay licensing fees or settle with patent holders, Apple often seeks to redesign its technology in ways that circumvent the disputed claims .
This strategy has both benefits and risks:
Benefits: Apple maintains control over its technology roadmap and avoids setting precedent for royalty payments
Risks: Legal battles can drag on for years, and losing a jury verdict (like the $634 million Masimo win) can be costly
The successful approval from U.S. Customs for the redesigned feature suggests this approach is working—at least for now.
Health Features as Competitive Moat
Apple's aggressive pursuit of health features on the Apple Watch—including blood oxygen, ECG, heart rate monitoring, and sleep apnea detection—reflects a broader strategic vision. Health tracking has become a primary reason consumers choose Apple Watch over competing wearables .
By fighting to restore blood oxygen monitoring rather than abandoning the feature, Apple signals that health capabilities are non-negotiable components of its product strategy. This commitment is likely to continue with future Apple Watch models expected to add features like blood pressure monitoring .
Implications for the Wearables Industry
The Apple-Masimo dispute has broader implications for the wearables industry. It highlights the tension between tech companies adding medical-grade features and established medical device manufacturers protecting their intellectual property.
Other companies—including Samsung, Garmin, and Fitbit—offer blood oxygen monitoring on their devices and are likely watching these legal proceedings closely. Depending on how the Apple-Masimo dispute ultimately resolves, the industry could see more licensing agreements, more design-around innovations, or continued litigation .
Future Outlook: What's Next for Apple Watch Health Features
Upcoming Apple Watch Models
According to industry reports, Apple is preparing significant updates for its 2026 Apple Watch lineup . Expected features include:
Doubled sensor components for improved accuracy
Exterior design alterations
Improved power efficiency
Potential blood pressure detection (though non-invasive blood glucose monitoring remains uncertain due to medical regulations and patent disputes)
The Blood Oxygen Feature: Long-Term Viability
With the ITC's preliminary ruling favoring Apple's redesign and U.S. Customs already having approved the feature, blood oxygen monitoring appears likely to remain available on Apple Watch models going forward.
However, the legal landscape remains complex. Masimo has separately sued U.S. Customs over its approval of the redesigned watches, and the full ITC has yet to ratify the judge's preliminary ruling . The $634 million jury verdict also remains unresolved pending appeal.
A New Era of Health Tracking
Regardless of how the Masimo dispute resolves, Apple shows no signs of slowing its health technology ambitions. The company has positioned the Apple Watch as an indispensable health companion, capable of detecting everything from irregular heart rhythms to signs of sleep apnea .
For consumers, this means the Apple Watch will likely continue gaining new health capabilities—even if the path to bringing those features to market occasionally involves navigating complex legal and regulatory challenges.
How to Get Started with Blood Oxygen Monitoring
If you own a compatible Apple Watch and want to start using the restored blood oxygen feature:
Step 1: Update Your Devices
iPhone: Go to Settings > General > Software Update and install iOS 18.6.1 or later .
Apple Watch: Open the Watch app on your iPhone, go to General > Software Update, and install watchOS 11.6.1 or later .
Step 2: Enable the Feature
Open the Watch app on your iPhone
Tap Blood Oxygen
Turn on the switch for Blood Oxygen Recordings if it's not already enabled .
Step 3: Configure Background Measurements
Decide whether to allow background readings
Consider disabling the feature during Sleep Focus or Theater Mode if the red light is disruptive .
Step 4: Take Your First Reading
Open the Blood Oxygen app on your Apple Watch
Rest your wrist on a flat surface
Tap Start and remain still for 15 seconds
After completion, check your reading in the Health app on your iPhone .
Step 5: Monitor Your Data
Regularly check your readings in the Health app to establish your personal baseline
Pay attention to consistent readings below 95%, which may warrant a conversation with your healthcare provider .
Frequently Asked Questions
Is the blood oxygen feature back on all Apple Watches?
No. The redesigned feature is available on Apple Watch Series 9, Series 10, and Ultra 2 that previously had the feature disabled. Series 6, 7, 8, and original Ultra models purchased before the ban continue using the original implementation .
Why can't I see my blood oxygen reading on my watch anymore?
With the redesigned feature, all results are displayed exclusively in the Health app on your iPhone. The watch no longer shows SpO2 readings directly due to the patent workaround .
Is the feature accurate?
The sensor technology is the same as before. However, Apple notes that measurements are for fitness and wellness purposes only and are not intended for medical diagnosis . Accuracy is best when the watch is properly fitted and the wearer remains still during measurements.
Will Apple have to remove the feature again?
The recent ITC preliminary ruling suggests the redesigned feature does not infringe Masimo's patents, making another removal unlikely. However, the legal situation remains fluid pending final ITC ratification and the outcome of Apple's appeal of the $634 million verdict .
Does this affect my Apple Watch if I bought it outside the US?
No. International Apple Watch units never lost blood oxygen functionality and continue working as originally designed .