Do these 3 things before closing this tab:
1Repair Windows errors before they cause bigger problems2Fix the driver behind crashes, sound loss and screen glitches3Clear out junk files and repair common Windows errorsApple Watch estimates blood oxygen using light reflected from tissue, but availability and where the final calculation happens depend on the watch’s model, region, purchase date, and—in some U.S. cases—part number. The U.S. restriction began with a patent dispute involving Masimo; Apple later introduced a redesigned feature for some U.S. watches that sends sensor data to the paired iPhone for the oxygen-saturation calculation. Apple says the feature is for general fitness and wellness, not medical use.
How Apple Watch blood oxygen works
Pulse oximetry estimates oxygen saturation by shining selected wavelengths of light into tissue and measuring the light that returns. Apple Watch uses optical sensors to gather signals from the wrist; the resulting percentage is an estimate, not a direct measurement of oxygen in the blood.
For the redesigned U.S. feature, the watch records optical sensor data and the paired iPhone calculates the oxygen-saturation value. Apple says results are viewed in the Respiratory section of the iPhone Health app. This is a change to the processing path, not an absence of an optical sensor in the watch.
How to take a reading
- Wear the watch snugly but comfortably, with its back in contact with your skin.
- Open the Blood Oxygen app on the watch where the feature is available.
- Rest your wrist flat and keep still while the 15-second measurement runs.
- For eligible redesigned U.S. watches, check the result in the Respiratory section of the paired iPhone’s Health app.
Apple says background readings may also occur when you are not moving, but their timing and number vary with activity. A reading may fail because of movement, poor fit, posture, cold or low skin perfusion, tattoos that block light, or a resting heart rate above 150 beats per minute. These are Apple’s listed factors, not a complete explanation of every failed reading.
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![Apple Watch Series 11 [GPS 46mm] Smartwatch with Jet Black Aluminum Case with Black Sport Band - M/L. Sleep Score, Fitness Tracker, Health Monitoring, Always-On Display, Water Resistant](https://m.media-amazon.com/images/I/416RQ0rtsUL._SL160_.jpg)
- 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.*
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- 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.
Is Apple Watch blood oxygen accurate?
The watch provides an estimate for general fitness and wellness. The dossier’s sources do not establish a controlled head-to-head accuracy comparison between Apple Watch versions or support a claim that its readings match a clinical pulse oximeter. Do not use a watch reading to diagnose a condition, make treatment decisions, or replace medical advice.
Apple Support says its Blood Oxygen measurements are not intended for medical use and are designed only for general fitness and wellness purposes. Apple gives 95–100% as a typical range, while noting that some people live normally below 95% and readings can be slightly lower during sleep. This range is not a diagnostic cutoff.
Why Apple Watch blood oxygen was restricted in the U.S.
Masimo alleged that Apple’s importation and sale of watches using light-based pulse oximetry technology infringed its patents. The U.S. International Trade Commission found a violation and issued an exclusion order covering infringing Apple Watches with that functionality. On March 19, 2026, the Federal Circuit affirmed the original ITC determination and order.
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![Apple Watch Series 11 [GPS 42mm] Smartwatch with Rose Gold Aluminum Case with Light Blush Sport Band - S/M. Sleep Score, Fitness Tracker, Health Monitoring, Always-On Display, Water Resistant](https://m.media-amazon.com/images/I/31caPPnRysL._SL160_.jpg)
- 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.
This was a patent and import dispute, not a finding that blood oxygen measurement generally was unsafe or that the FDA had rejected the feature. Apple initially complied with the restriction by importing a redesign with the feature disabled. It later developed a different implementation that changes where the final calculation takes place.
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What changed in the redesigned U.S. feature
In the redesigned implementation, the watch’s sensors collect optical data and the paired iPhone computes the oxygen-saturation value. Apple announced the feature for some U.S. users in August 2025. Customs allowed importation of this second redesign on August 1, 2025, and the ITC’s April 2026 enforcement determination found its importation did not violate the existing exclusion order.
The latest legal milestone in the dossier is that April 2026 determination. Masimo’s filing gave June 16, 2026 as the appeal deadline, but later appeal status was not verified. It would therefore be premature to say that all litigation has ended.
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![Apple Watch Series 11 [GPS 42mm] Smartwatch with Jet Black Aluminum Case with Black Sport Band - S/M. Sleep Score, Fitness Tracker, Health Monitoring, Always-On Display, Water Resistant](https://m.media-amazon.com/images/I/41s72HIk5TL._SL160_.jpg)
- 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.
Which Apple Watch models support blood oxygen?
Apple says the Blood Oxygen app is available on Apple Watch Series 6 or later and all Apple Watch Ultra models in certain regions. Apple Watch SE does not support it. Availability in the United States also depends on purchase date and part number, so a model name alone is not enough to determine how the feature works.
| Situation | What to know |
|---|---|
| Apple Watch SE | Does not support the Blood Oxygen app. |
| Series 6 or later, or any Ultra | Supported in certain countries and regions, subject to Apple’s availability rules. |
| Eligible U.S. Series 9, Series 10, or Ultra 2 | Some users received the redesigned feature; sensor data is sent to the paired iPhone for calculation. |
| U.S. unit purchased on or after January 18, 2024, with part number ending LW/A or LS/A | Apple says analysis occurs on the paired iPhone and results appear in Health. |
| Earlier U.S. purchase with the original feature | Apple says previously purchased units with the original feature were unaffected by the later redesign rollout. |
Apple’s August 2025 announcement said some Series 9, Series 10, and Ultra 2 users without the original feature could receive the redesigned feature with iOS 18.6.1 and watchOS 11.6.1. Check Apple’s current support information for your exact device and region rather than assuming every watch of the same generation behaves alike.
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What to check if you are buying or troubleshooting
- Check the watch family and generation; SE does not support the feature.
- Check the country or region where the watch was sold.
- For a U.S. watch, check the purchase date and part-number suffix; Apple identifies January 18, 2024 and the LW/A or LS/A suffix for the redesigned processing path.
- Update the paired iPhone and watch software if you are checking eligibility for the redesigned feature.
- Decide whether you want general wellness context or medical measurement; Apple Watch is not intended for the latter.
FAQ
Does Apple Watch measure blood oxygen continuously?
No. Apple describes a 15-second on-demand reading, and background readings may happen when you are not moving. Their timing and number vary with activity.
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![Apple Watch SE 3 [GPS 40mm] Smartwatch with Starlight Aluminum Case with Starlight Sport Band - S/M. Fitness and Sleep Trackers, Heart Rate Monitor, Always-On Display, Water Resistant](https://m.media-amazon.com/images/I/31YiTby0pOL._SL160_.jpg)
- 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.*
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Can Apple Watch measure blood oxygen in the U.S.?
Some U.S. users can access the redesigned feature, but eligibility depends on the watch, purchase date, part number, software, and Apple’s availability rules. For the redesigned implementation, the watch gathers sensor data and the paired iPhone calculates the result.
Does my Apple Watch have a blood oxygen sensor?
Apple lists Series 6 or later and all Ultra models as supported in certain regions; SE is not supported. For U.S. watches, check the specific purchase and part-number conditions as well as the model generation.
Why might a reading fail?
Apple lists factors including movement, poor fit, posture, cold or low skin perfusion, tattoos that block light, and a resting heart rate above 150 beats per minute. Wear the watch snugly but comfortably, rest your wrist flat, and stay still during the measurement.
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![Apple Watch Series 11 [GPS 42mm] Smartwatch with Space Gray Aluminum Case with Black Sport Band - S/M. Sleep Score, Fitness Tracker, Health Monitoring, Always-On Display, Water Resistant](https://m.media-amazon.com/images/I/41yzp82pFOL._SL160_.jpg)
- 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.
Can I use the reading to diagnose a health problem?
No. Apple says the feature is for general fitness and wellness, not medical use, self-diagnosis, or consultation with a doctor. Talk with a healthcare professional about health concerns.
Sources
Apple Support, “Monitor your blood oxygen levels with the Blood Oxygen app on Apple Watch” [c001]; Apple Newsroom, announcement of the redesigned U.S. Blood Oxygen feature, August 14, 2025 [c002]; Federal Circuit opinion on the ITC determination [c003, c005]; U.S. Customs determination on the second redesign [c004]; Masimo SEC filing on the dispute and appeal deadline [c005, c006].
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