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One free scan finds every outdated or missing driver and matches the right update for your exact hardware.Free scan · exact hardware matchApple restored Blood Oxygen functionality for certain U.S. Apple Watch users through the iOS 18.6.1 and watchOS 11.6.1 updates, released August 14, 2025. The affected watches are the U.S. versions of Apple Watch Series 9, Series 10, and Apple Watch Ultra 2 that shipped without Blood Oxygen. Both the paired iPhone and the watch must be updated.
This was not a new sensor feature, and iOS 18.6.1 is not the latest iPhone software as of 2026. It was the historically important update that introduced Apple’s redesigned U.S. Blood Oxygen workflow: the watch collects the optical signals, but the paired iPhone performs the calculation and displays the result in the Health app.
What iOS 18.6.1 changed for Apple Watch
Apple’s August 14, 2025 release enabled a redesigned Blood Oxygen experience for some U.S. Apple Watch Series 9, Series 10, and Apple Watch Ultra 2 units that previously lacked the feature.
The key detail is that Apple did not add a new blood-oxygen sensor. The affected watches already contained the necessary optical hardware. Instead, Apple changed where the final blood-oxygen calculation takes place:
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Outbyte PC Repair FREERepair Windows errors before they cause bigger problemsFix Now →Outbyte Driver Updater FREEScan for outdated or missing drivers - takes under a minuteDriver Scan →- Apple Watch: collects the photoplethysmography signals using its optical sensors.
- Paired iPhone: processes those signals and calculates the Blood Oxygen result.
- Health app: stores and displays the saved measurements on the iPhone.
That makes this a two-device feature. Updating only the Apple Watch is not enough for the redesigned U.S. experience.
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- 【Comprehensive 24/7 Health Monitoring】The fitness watches for women and men packs 24/7 heart rate, 24/7 blood pressure and blood oxygen monitors. You could check those real-time health metrics anytime, anywhere on your wrist and view the data record in the App. The heart rate monitor watch also tracks different sleep stages for light and deep sleep,and the time when you wake up, helps you to get a better understanding of your sleep quality.
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- 【Essential Assistant for Daily Life】The fitness watches for women and men provide you with more features including drinking water and sedentary reminder, women's menstrual period reminder, breath training, real-time weather display, remote camera shooting, music control,timer, stopwatch, finding phone, alarm clock, making it a considerate life assistant. With the GPS connectivity, you could get a map of your workout route in the app for outdoor activity by connecting to your phone GPS.
Who is eligible?
Apple’s restoration applies to a specific group:
- You are in the United States.
- You have a U.S. Apple Watch Series 9, Series 10, or Apple Watch Ultra 2 that currently does not show Blood Oxygen.
- The watch is paired with a compatible iPhone.
- The iPhone is updated to iOS 18.6.1 or a later software version that preserves the redesigned experience.
- The watch is updated to watchOS 11.6.1 or later.
Apple Watch units purchased outside the U.S. were not affected by this particular restoration announcement. International availability follows the rules for the relevant country or region, rather than the U.S. update alone.
Apple also says Blood Oxygen is available on Apple Watch Series 6 or later and all Apple Watch Ultra models in supported countries and regions. However, the U.S. models involved in this specific change are the Series 9, Series 10, and Ultra 2 versions that were sold without the original feature.
The feature is not supported on Apple Watch SE or on Apple Watch models configured for Apple’s Apple Watch For Your Kids setup. Apple also states that Blood Oxygen is intended for people aged 18 and older.
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Model names do not always tell the whole story. Apple Support says that certain U.S. watches purchased on or after January 18, 2024 have part numbers ending in LW/A. Those models use iPhone-based Blood Oxygen data analysis and display the results in the iPhone Health app.
If your watch is a U.S. Series 9, Series 10, or Ultra 2 but the feature does not appear after updating, check its part-number information and regional configuration. A watch’s retail name by itself may not identify whether it uses the original watch-based experience or the redesigned iPhone-based arrangement.
How to turn Blood Oxygen back on
For an affected U.S. watch, follow this order:
- Update the paired iPhone. Open Settings > General > Software Update and install iOS 18.6.1 or the applicable later release.
- Update the Apple Watch. On the iPhone, open the Watch app and go to My Watch > General > Software Update. You can also update from the watch where supported.
- Open Blood Oxygen on the watch. Follow the on-screen instructions to begin a measurement.
- Wear the watch correctly. It should be snug but comfortable, with the back of the watch touching your skin.
- Keep your wrist still and flat. The on-demand measurement takes about 15 seconds when conditions are suitable.
- View the saved result on the iPhone. Open Health > Search > Respiratory > Blood Oxygen.
Because the iPhone performs the calculation, it should remain near enough to communicate with the watch during the process. The exact prompts may vary depending on the watch model, software version, region, and whether Blood Oxygen has already been configured.
Where to find your results
Unlike the original experience on supported watches, the redesigned U.S. setup is centered on the iPhone. Measurements are saved in the Health app, where you can view trends over time, including daily, weekly, monthly, and six-month views. Apple’s Health documentation also describes relevant sleep and high-elevation filters where applicable.
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Use this path:
Health > Search > Respiratory > Blood Oxygen
If you are looking for a result on the watch itself, you may be looking for the wrong part of the redesigned workflow. The watch remains the sensing device, but the iPhone is the calculation and results device.
What you will not get back
Apple describes this as a redesigned Blood Oxygen feature, not an exact restoration of the old user experience.
On the original configuration, a supported Apple Watch could show Blood Oxygen results directly through the watch-based system. On the affected U.S. models, the redesigned arrangement sends the sensor signals to the paired iPhone for processing. The result is then shown in Health on that iPhone.
In practical terms, expect the following differences:
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- 【Health Metrics Monitoring】These fitness watches for women and men pack 24/7 heart rate, blood oxygen, blood pressure monitors and sleep tracker. You could check those real-time health metrics anytime, anywhere conveniently on your wrist and check the all-day data record in the App.The sleep tracker keeps track of time spent in different sleep stages including REM, light sleep,deep sleep,and the time when you wake up, helps you to get a better understanding of your sleep quality.
- 【115 sports modes & All-Day Activity Tracking】There are more than 115 sports modes tracking available in the activity trackers and smartwatches, covering almost all daily sports activities you can imagine, gives you new ways to train and advanced metrics for more information about your workout performance.The all-day activity tracking feature monitors your steps, distance, and calories burned all the day, so you can see how much progress you've made towards your fitness goals.
- 【Notifications for Calls and Messages】Getting notifications for incoming calls and texts right away from your wrist while on the go, allowing you to stay connected with family and friends with calls, texts, and email, so you never miss an important call or message. You could see the caller's name, reject the call, mute the ring-tone, and read the whole text messages directly from the smart watch for android phones and iphone.
- 【A Considerate Life Assistant】The fitness trackers for women and men provide you with more features including drinking water reminder, sedentary reminder,menstrual cycle reminder, real-time weather display, remote camera shooting, music control,timer,and do-not-disturb mode, making it a considerate life assistant.With the GPS connectivity, you could get a map of your workout route in the app for outdoor activity by connecting to your phone GPS.
- 【1.47" HD-color Full Touch Screen】The curved-design 1.47" HD-color display and full touch screen ensures better visual and operating experience, everything is easier to see and operate, making this fitness tracker as intuitive to use as it is beautiful to look at.There are more than 150 watch face options for you to choose from in the App. You could also customize the smart watch face with photos from your own album. So it's easy to find the right look for the right moment.
- The watch collects the measurement but does not perform the final calculation in the same way as the original configuration.
- The iPhone is an essential part of the process.
- Saved results are viewed in the iPhone Health app.
- The feature should not be described as identical to Blood Oxygen on an unaffected international model or an older U.S. unit that retained the original functionality.
Why Blood Oxygen disappeared in the first place
The U.S. availability problem followed the patent dispute between Apple and Masimo involving wearable devices and light-based pulse-oximetry technology.
Apple’s redesigned configuration moved the relevant processing from the watch to the iPhone. Materials from U.S. Customs and Border Protection describe a configuration in which the watch transmits photoplethysmography signals to the iPhone, where processing and notification of the results occur. Apple said a recent CBP ruling enabled the update that restored the experience for eligible U.S. users.
That legal explanation needs careful wording. A CBP ruling concerns customs admissibility and whether Apple’s redesigned configuration falls within the relevant exclusion-order requirements. It should not be presented as a final resolution of every issue in the wider Apple-Masimo patent dispute or of all related U.S. International Trade Commission proceedings.
Troubleshooting when Blood Oxygen still does not appear
1. Confirm that both devices are updated
Check the iPhone under Settings > General > Software Update. Then check the watch in the iPhone’s Watch > My Watch > General > Software Update section.
If only the watch was updated, install the required iPhone update as well. The iPhone update is central to the redesigned processing system.
2. Check the country and purchase configuration
The restoration described here is U.S.-specific. A watch purchased in another country may follow different regional availability rules, while a U.S. watch may have a configuration that differs from another unit with the same retail model name.
3. Check whether the watch is supported
Apple Watch SE does not support the Blood Oxygen app, and the feature is unavailable in Apple Watch For Your Kids configurations. The U.S. restoration specifically concerns Series 9, Series 10, and Ultra 2 units that lacked Blood Oxygen.
4. Check the part number
For U.S. models purchased on or after January 18, 2024, a part number ending in LW/A can indicate the iPhone-based analysis configuration described by Apple Support. Use the part number together with the watch’s region, purchase date, and software versions rather than relying on the model name alone.
5. Recheck the Health app location
Results should be under Health > Search > Respiratory > Blood Oxygen. If the app has not completed setup, open Blood Oxygen on the watch first and take a fresh measurement.
6. Improve the measurement conditions
Keep the wrist still and flat for the roughly 15-second reading. Wear the watch snugly but comfortably and ensure the back is in contact with the skin. Movement, an overly loose fit, or poor contact can prevent a usable reading.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Should you buy an Apple Watch specifically for Blood Oxygen?
In the U.S., do not assume that every listing with the same model name has the same Blood Oxygen behavior. Regional availability and part-number configuration matter.
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- 【Advanced Health Fitness Tracker】-This fitness tracker offers 24/7 heart rate and blood pressure monitoring to help you stay proactive about your health goals. It also supports on-demand blood oxygen checks, so you can quickly see your O₂ level whenever you need it. Detailed sleep tracking (deep sleep, light sleep and wake-ups) and all-day activity tracking give you a clearer picture of your overall health trends. (Inspire a healthy life, not for medical use
- 【All-Day Activity & Fitness Tracking】-The MorePro fitness tracker for women and men offers 120+ sport modes including running, walking and more, so you can track the workouts you actually do. With a built-in pedometer step counter, this smart watch records steps, distance, calories burned, heart rate and training time in real time, giving you clear references for exercise intensity. Whether you’re at the gym, on a run or playing ball with friends, every workout becomes safer, more efficient and easier to enjoy
- 【Women’s Health & Cycle Tracking】-Designed as a women’s health tracker, the smart watches for women offers intuitive menstrual cycle tracking right on your wrist. Use the built-in period tracker to log your menstrual period, safe days, ovulation window and ovulation day, while the app supports period mode, trying-to-conceive mode and pregnancy mode to match different life stages. Whether you’re at work, in class or relaxing at home, gentle women’s health reminders help you prepare in advance with the right clothes and pads, so every month feels more predictable and in control
- 【Everyday Smart Lifestyle Companion】-Stay connected without constantly checking your phone. This smart watch fitness tracker delivers real-time call, SMS and app message notifications on your wrist, so you can see who’s contacting you while you’re in a meeting, commuting or working out. The IP68 waterproof design easily handles sweat, rain and hand-washing. With over 200 watch faces and simple DIY custom faces using your own photos, you can quickly match your watch to business, workout or casual looks
- 【Practical Daily Smart Tools】-From sedentary reminders and drink water reminders to on-wrist weather forecasts, this smart watch helps you build healthier routines at work or while studying. Use music control and camera control while your phone stays in your bag, and rely on the stopwatch, timer, alarm clock and find my phone features to keep workouts, cooking and busy mornings on track
Apple explicitly names the Apple Watch Series 10 and Apple Watch Ultra 2 among the affected product families, but a buyer should verify the exact U.S. configuration and the seller’s description before purchasing. The presence of an eligible model name does not by itself guarantee the original watch-based Blood Oxygen experience; eligible U.S. units may use the redesigned iPhone-based workflow.
Do these 3 things before closing this tab:
1Fix the driver behind crashes, sound loss and screen glitches2Repair Windows errors before they cause bigger problems3Scan for outdated or missing drivers - takes under a minuteThe same caution applies to the Apple Watch Series 9. If Blood Oxygen is a deciding factor, confirm the country of sale, model and part number, supported software, and whether the listing describes a unit that currently lacks the feature and can use the U.S. restoration.
Blood Oxygen is not a medical diagnosis
Apple says Blood Oxygen measurements are intended for general fitness and wellness purposes. They are not intended for medical use, self-diagnosis, or consultation with a doctor.
Do not use an Apple Watch reading to diagnose a condition, decide that medical care is unnecessary, or replace professional advice. If you have symptoms or a health concern, contact a qualified medical professional. A separate fingertip pulse oximeter may be useful for comparison or backup only when its use is appropriate, but it should not be treated as automatically more accurate without checking the specific device’s regulatory status, instructions, and limitations.
Apple also notes that availability varies by country and region and that the feature is not intended for people under 18.
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Why the “surprise update” wording needs a date qualifier
iOS 18.6.1 was released on August 14, 2025 for iPhone XS and later. Apple’s security-release listing recorded no published CVE entries for that release, while Apple’s iOS 18 documentation identified the U.S. Blood Oxygen change as its notable feature addition.
As of 2026, iOS 18.6.1 should not be called the latest iPhone update. Apple released subsequent iOS 18 versions. The accurate description is that iOS 18.6.1 was the August 2025 update that enabled Apple’s redesigned U.S. Blood Oxygen experience for compatible Apple Watch models.
Frequently Asked Questions
Does iOS 18.6.1 restore Blood Oxygen on every Apple Watch?
No. The U.S. restoration targets certain Apple Watch Series 9, Series 10, and Apple Watch Ultra 2 units that were sold without Blood Oxygen. Apple Watch SE and Apple Watch For Your Kids configurations are not supported, and availability varies by country and region.
Do I need to update both my iPhone and Apple Watch?
Yes. Affected users need the paired iPhone updated to iOS 18.6.1 and the compatible watch updated to watchOS 11.6.1 or later. The iPhone is part of the redesigned system because it performs the final Blood Oxygen calculation.
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One free scan finds every outdated or missing driver and matches the right update for your exact hardware.Free scan · exact hardware matchWhere are Apple Watch Blood Oxygen results saved?
On the affected U.S. configuration, open the iPhone Health app and go to Health > Search > Respiratory > Blood Oxygen.
Can the Apple Watch Blood Oxygen reading diagnose a health problem?
No. Apple describes the feature as intended for general fitness and wellness, not medical use or self-diagnosis. It should not replace professional medical advice or evaluation.
Is iOS 18.6.1 still the latest iOS version?
No. It was the August 14, 2025 release that enabled the redesigned U.S. Blood Oxygen experience. Later iOS 18 releases followed, so users should install the current compatible software offered for their iPhone rather than seek out 18.6.1 as the newest version.
The Bottom Line
Bottom line: Apple’s Blood Oxygen return was real but limited. For affected U.S. Apple Watch Series 9, Series 10, and Ultra 2 units, update both devices, take the reading on the watch, and view the iPhone-calculated result in Health > Search > Respiratory > Blood Oxygen. It is a redesigned wellness feature—not a new sensor, not the exact original watch-only experience, and not a medical diagnostic tool.
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