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1Repair Windows errors before they cause bigger problems2Scan for outdated or missing drivers - takes under a minute3Clear out junk files and repair common Windows errorsApple Watch Blood Oxygen is already back in the U.S. Apple restored a redesigned version on August 14, 2025, for eligible U.S. Apple Watch Series 9, Series 10, and Apple Watch Ultra 2 units that originally shipped without the feature. The original July 2025 framing that it “might” return is now outdated.
To enable it, the paired iPhone originally needed iOS 18.6.1 and the watch needed watchOS 11.6.1. Apple’s current guidance is to install the latest compatible versions of both operating systems. The main difference from the old experience is that the watch collects the sensor data, while the paired iPhone calculates the result and shows it in the Health app under Respiratory.
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The short answer
If you own a U.S. Apple Watch Series 9, Series 10, or Ultra 2 that previously lacked Blood Oxygen, you generally do not need to buy a new watch. Update both the paired iPhone and Apple Watch, then look in the iPhone’s Health app under Health > Respiratory.
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- GET SMARTER HEALTH INSIGHTS—Apple Watch SE 3 is an advanced health tracker that helps you better understand your body. The smartwatch sends alerts for an irregular heart rhythm, or an unusually high or low heart rate.* You can view your overnight health tracking metrics with the Vitals app,* track your sleep score, and get sleep apnea notifications.*
- A GREAT FITNESS TRACKER—SE 3 can track your workouts in a healthy number of ways—from running and strength training to simply achieving your 10K steps a day. With real-time metrics and Workout Buddy powered by Apple Intelligence from your nearby iPhone,* you’ll hit your goals like never before.
- KEEP HELP CLOSE AT HAND—SE 3 is a smartwatch that can detect a hard fall or severe car crash and automatically help connect you to emergency services and notify your emergency contacts.* Check In can automatically notify a loved one when you’ve arrived at your destination.
- WOMEN’S HEALTH INSIGHTS—SE 3 has advanced sensors that track your wrist temperature while you sleep. With this smartwatch, you can log your periods and symptoms, get period predictions, and get notified of cycle deviations.*
- GREAT BATTERY LIFE AND FASTER CHARGING—Enjoy a smartwatch with all-day, 18-hour battery life* from sunup to sundown. Then charge up to twice as fast as SE 2* and get up to 8 hours of battery in just 15 minutes.*
Why Blood Oxygen disappeared from some U.S. Apple Watches
The feature became entangled in Apple’s patent dispute with Masimo. The U.S. International Trade Commission found that Apple infringed Masimo pulse-oximetry patents, affecting the import and sale of certain Apple Watch models in the United States.
To continue selling affected watches, Apple sold U.S. versions of the Series 9 and Ultra 2 without Blood Oxygen functionality. The watches generally retained the relevant hardware, but the feature was disabled through software. The sales workaround and the earlier dispute were reported in January 2024 coverage by BGR.
In July 2025, Apple’s appeal and the possibility of a redesigned implementation prompted headlines suggesting that Blood Oxygen might return. Apple later said a U.S. Customs ruling enabled its software solution. That does not, by itself, establish that every issue in the broader Masimo litigation was permanently resolved or that Apple prevailed on every legal question.
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When did Blood Oxygen return?
The U.S. restoration was announced on August 14, 2025. The enabling versions were:
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- A FULL-FEATURED HEALTH TRACKER—Apple Watch Series 11 gives you invaluable insights about your body, right from your wrist. Take an ECG anytime* and get alerts for a high and low heart rate or an irregular rhythm*—so you can stay closer to your heart. You can also view your overnight health tracking metrics with the Vitals app* and be notified of possible sleep apnea.*
- KNOW YOUR SLEEP SCORE—With advanced sleep tracking, Series 11 gives you a daily sleep score. It’s an easy way to help measure and understand the quality of your sleep, so you can make it more restorative.
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- iOS 18.6.1 on the paired iPhone
- watchOS 11.6.1 on the Apple Watch
Those are the minimum versions associated with the original reactivation. In 2026, do not deliberately remain on them: install the latest compatible iOS and watchOS releases available for your devices.
Which Apple Watches qualify?
Apple specifically named these model families:
- Apple Watch Series 9
- Apple Watch Series 10
- Apple Watch Ultra 2
The relevant watches are U.S. units that previously lacked Blood Oxygen because of the sales restriction. Eligibility also depends on the watch’s sales region and software state.
Keep these three groups separate:
- U.S. watches that originally included Blood Oxygen: Apple said previously purchased units with the original feature were unaffected.
- U.S. Series 9, Series 10, and Ultra 2 units sold without it: These are the watches targeted by the redesigned U.S. experience.
- Watches purchased outside the U.S.: Apple said the U.S. redesign did not affect them; their behavior follows the feature implementation associated with their market.
Apple’s watchOS 11 update documentation also identifies Series 9, Series 10, and Ultra 2 as the models receiving the new U.S. Blood Oxygen experience. Do not interpret this as a blanket feature addition for every Apple Watch model.
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How the redesigned feature works
The architecture is the most important practical difference:
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- A FULL-FEATURED HEALTH TRACKER—Apple Watch Series 11 gives you invaluable insights about your body, right from your wrist. Take an ECG anytime* and get alerts for a high and low heart rate or an irregular rhythm*—so you can stay closer to your heart. You can also view your overnight health tracking metrics with the Vitals app* and be notified of possible sleep apnea.*
- KNOW YOUR SLEEP SCORE—With advanced sleep tracking, Series 11 gives you a daily sleep score. It’s an easy way to help measure and understand the quality of your sleep, so you can make it more restorative.
- GET HYPERTENSION NOTIFICATIONS—Did you know that Series 11 can spot signs of chronic high blood pressure? By analyzing how your blood vessels respond to beats of the heart, it can notify you of possible hypertension.*
- SAFETY FEATURES—A smartwatch that puts your safety first. Series 11 can detect a hard fall or severe car crash, automatically help connect you with emergency services, and notify your emergency contacts.* Check In can automatically notify a loved one when you’ve arrived at your destination.
- A POWERFUL FITNESS TRACKER—With advanced metrics and motivating features like Pacer, Heart Rate Zones, training load, and Workout Buddy powered by Apple Intelligence from your nearby iPhone*—Series 11 is made to help everyone stay active, from runners and hikers to strength-training enthusiasts.
- The Apple Watch collects the sensor data.
- The paired iPhone calculates the measurement.
- The result is displayed in the iPhone’s Health app under Respiratory.
That means “Blood Oxygen is back” does not necessarily mean the watch will behave exactly like an international model or an older U.S. watch that had the original implementation. Users expecting the old watch-centric workflow may look in the wrong place or assume the update failed.
Apple’s feature-availability documentation is also worth checking when comparing regional behavior. Availability can vary by model and country or region.
How to restore Blood Oxygen on an eligible watch
- Identify the model. Confirm that the watch is a Series 9, Series 10, or Ultra 2.
- Check the sales region. The redesigned restoration concerns qualifying U.S. units that previously lacked the feature.
- Update the iPhone. The original enabling requirement was iOS 18.6.1 or later.
- Update the watch. The original enabling requirement was watchOS 11.6.1 or later.
- Keep the devices paired. The iPhone performs the calculation, so the paired phone is part of the redesigned workflow.
- Open Health on the iPhone. Go to Health > Respiratory and look for Blood Oxygen results.
If you are updating now, use the latest compatible releases rather than treating iOS 18.6.1 and watchOS 11.6.1 as current targets. Those versions explain how the feature was originally restored, not a recommendation to skip later security and compatibility updates.
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Work through these checks before considering a replacement:
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- GET SMARTER HEALTH INSIGHTS—Apple Watch SE 3 is an advanced health tracker that helps you better understand your body. The smartwatch sends alerts for an irregular heart rhythm, or an unusually high or low heart rate.* You can view your overnight health tracking metrics with the Vitals app,* track your sleep score, and get sleep apnea notifications.*
- A GREAT FITNESS TRACKER—SE 3 can track your workouts in a healthy number of ways—from running and strength training to simply achieving your 10K steps a day. With real-time metrics and Workout Buddy powered by Apple Intelligence from your nearby iPhone,* you’ll hit your goals like never before.
- KEEP HELP CLOSE AT HAND—SE 3 is a smartwatch that can detect a hard fall or severe car crash and automatically help connect you to emergency services and notify your emergency contacts.* Check In can automatically notify a loved one when you’ve arrived at your destination.
- WOMEN’S HEALTH INSIGHTS—SE 3 has advanced sensors that track your wrist temperature while you sleep. With this smartwatch, you can log your periods and symptoms, get period predictions, and get notified of cycle deviations.*
- GREAT BATTERY LIFE AND FASTER CHARGING—Enjoy a smartwatch with all-day, 18-hour battery life* from sunup to sundown. Then charge up to twice as fast as SE 2* and get up to 8 hours of battery in just 15 minutes.*
- Verify that both the iPhone and watch are fully updated.
- Confirm that the watch is paired with the iPhone you are checking.
- Look in Health > Respiratory on the iPhone instead of expecting the old feature location on the watch.
- Confirm that the model is a Series 9, Series 10, or Ultra 2.
- Confirm that it is a qualifying U.S. unit that previously lacked the function.
- Restart both devices and give the updated Health data time to appear.
- Contact Apple Support if the feature remains unavailable after the eligibility and software checks.
Some Apple Community users reported that taking an ECG appeared to make Blood Oxygen work after updating. That is an anecdotal report, not an Apple-documented procedure or guaranteed fix. Do not treat an ECG as a required activation step.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Do you need to buy a new Apple Watch?
Usually, no. If you already own an eligible affected U.S. Series 9, Series 10, or Ultra 2, Apple’s solution was a software update. Update that watch before considering a replacement.
A new watch may still make sense if your current model is older and incompatible, damaged or unsupported, or if you want newer hardware, battery life, or health features unrelated to Blood Oxygen. It is not sensible to buy an expensive Ultra solely to solve a feature-eligibility problem without first checking the watch you already own.
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- A FULL-FEATURED HEALTH TRACKER—Apple Watch Series 11 gives you invaluable insights about your body, right from your wrist. Take an ECG anytime* and get alerts for a high and low heart rate or an irregular rhythm*—so you can stay closer to your heart. You can also view your overnight health tracking metrics with the Vitals app* and be notified of possible sleep apnea.*
- KNOW YOUR SLEEP SCORE—With advanced sleep tracking, Series 11 gives you a daily sleep score. It’s an easy way to help measure and understand the quality of your sleep, so you can make it more restorative.
- GET HYPERTENSION NOTIFICATIONS—Did you know that Series 11 can spot signs of chronic high blood pressure? By analyzing how your blood vessels respond to beats of the heart, it can notify you of possible hypertension.*
- SAFETY FEATURES—A smartwatch that puts your safety first. Series 11 can detect a hard fall or severe car crash, automatically help connect you with emergency services, and notify your emergency contacts.* Check In can automatically notify a loved one when you’ve arrived at your destination.
- A POWERFUL FITNESS TRACKER—With advanced metrics and motivating features like Pacer, Heart Rate Zones, training load, and Workout Buddy powered by Apple Intelligence from your nearby iPhone*—Series 11 is made to help everyone stay active, from runners and hikers to strength-training enthusiasts.
If you need dependable oxygen-saturation readings for a medical reason, consider an appropriate FDA-authorized medical pulse oximeter or a clinician-recommended device rather than choosing a smartwatch as a clinical instrument.
Blood Oxygen is not a medical diagnosis
Apple Watch Blood Oxygen is a wellness and fitness feature, not a substitute for clinical pulse-oximetry equipment or medical advice. Do not use its readings to diagnose low oxygen, change treatment, or dismiss symptoms.
Seek medical care for urgent symptoms such as breathing difficulty, chest pain, confusion, or blue lips. A smartwatch reading should never delay emergency help.
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As of August 18, 2026: Apple Watch Blood Oxygen has returned to eligible U.S. Series 9, Series 10, and Ultra 2 watches that previously lacked it. The feature is redesigned, depends on the paired iPhone for calculation, and reports results in the iPhone Health app’s Respiratory section. Existing owners should update first; most do not need a new Apple Watch.
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