Ever had that moment when you realize your Apple Watch could be doing more for your health, only to find out a feature’s been locked away? For folks in the U.S. with an Apple Watch Series 9, Series 10, or Ultra 2, that missing piece—blood oxygen monitoring—is back in a big way. On August 14, 2025, Apple rolled out iOS 18.6.1 and watchOS 11.6.1, delivering a redesigned Blood Oxygen experience that’s got me buzzing. As a tech nerd who’s spent way too many mornings checking heart rate stats and geeking out over Apple’s health tech, I’m thrilled to see this feature return after a year-and-a-half legal saga. In this blog, I’m diving into the confirmed details of this update, weaving a story that’s as fun as a perfectly timed workout alert and packed with everything you need to know. Let’s unpack what iOS 18.6.1 and watchOS 11.6.1 bring, how the new Blood Oxygen feature works, and why it’s a game-changer for U.S. users—stick around, it’s worth the read!
What’s the Deal with iOS 18.6.1 and watchOS 11.6.1?
Apple dropped iOS 18.6.1 and watchOS 11.6.1 on August 14, 2025, with one clear mission: bring back blood oxygen monitoring for U.S. users of Apple Watch Series 9, Series 10, and Ultra 2. This update is a direct response to an 18-month patent dispute with medical tech company Masimo, which forced Apple to disable the feature on U.S.-sold watches starting in January 2024. Thanks to a recent U.S. Customs Service ruling, Apple found a clever workaround to restore it, and I’m stoked to see how it plays out.
The updates are available for:
- iPhones: Any model running iOS 18, from iPhone Xs, Xs Max, and Xr to the latest iPhone 16 series.
- Apple Watches: Series 9, Series 10, and Ultra 2 models purchased in the U.S. after January 2024, which shipped without blood oxygen monitoring.
These updates are laser-focused on the Blood Oxygen feature, with no other confirmed changes like new emojis or major bug fixes. I was refreshing my iPhone’s Software Update screen like a kid on Christmas morning, ready to see this feature light up my friend’s Series 10.
How Does the New Blood Oxygen Feature Work?
The revamped Blood Oxygen experience is a smart sidestep around Masimo’s patents. Here’s the confirmed breakdown, straight from Apple’s release notes and newsroom:
- Data Collection on Your Watch: Fire up the Blood Oxygen app on your Apple Watch Series 9, Series 10, or Ultra 2. The watch’s sensors use red and infrared light to measure how light reflects off blood vessels in your wrist, collecting raw data on oxygen levels.
- Processing on Your iPhone: Unlike the original feature, which showed results right on the watch, this version sends the data to your paired iPhone running iOS 18.6.1. The iPhone crunches the numbers to calculate your blood oxygen percentage, typically 95%–100% for healthy folks.
- Results in the Health App: Your readings pop up in the Respiratory section of the iPhone’s Health app, where you can check your levels, view trends over time, and even export data for your doctor.
The catch? You won’t see instant results on your watch like older models (pre-2024) allowed. It’s a slight bummer, but I’m just happy to have the feature back. I can picture myself checking my stats after a trail run, marveling at how my lungs hold up in the mountains.
Who Can Use This Feature?
The redesigned Blood Oxygen feature is exclusive to:
- Apple Watch Series 9, Series 10, and Ultra 2 models sold in the U.S. after January 2024, which lacked blood oxygen monitoring due to the Masimo dispute.
- Users in the United States only, as the update doesn’t affect watches sold internationally or those with the original Blood Oxygen feature (like Series 6 or pre-2024 U.S. models).
Apple’s clear that there’s “no impact” to watches with the original feature or those sold outside the U.S. My buddy who snagged his Ultra 2 in Canada is unaffected, but I’m a tad jealous of U.S. users getting this shiny new update.
Why This Update Is a Big Win
This release is more than a software patch—it’s a victory lap for Apple and its U.S. users. Here’s why I’m hyped:
1. Health Tracking Gets a Boost
Blood oxygen levels are a window into your respiratory and circulatory health, helping spot issues like breathing difficulties or low oxygen saturation. It’s a must-have for fitness buffs, hikers hitting high altitudes, or anyone curious about their wellness. I remember borrowing a friend’s Series 6 to check my levels during a ski trip—it was wild to see how altitude played with my stats, and now U.S. users get that back.
2. Apple’s Legal Judo Move
The Masimo dispute, kicking off in 2020, claimed Apple infringed on patents for pulse oximetry (the tech behind blood oxygen monitoring), introduced with the Series 6. A 2023 U.S. International Trade Commission ruling banned sales of affected watches, forcing Apple to disable the feature in the U.S. The new iPhone-based processing, greenlit by U.S. Customs, dodges the patented watch-based calculations. It’s like Apple pulled off a tech ninja move, and I’m impressed by their hustle.
3. Keeps Apple Watch on Top
Apple Watch is a health tech titan, with features like ECG, irregular heart rhythm alerts, and Sleep Apnea Notifications. Bringing back blood oxygen monitoring cements its lead over competitors like Fitbit or Garmin. My gym partner’s been debating a Series 10 purchase, and this update might just seal the deal.
4. Empowering Users
The Health app’s Respiratory section lets you track trends, share data with doctors, or even spot patterns—like how your levels dip during intense workouts. I’m already planning to use it to compare my stats before and after yoga sessions, nerding out over the data.
The Backstory: Why Was Blood Oxygen Missing?
The Masimo saga started when Apple launched blood oxygen monitoring in 2020 with the Series 6. Masimo claimed Apple violated its pulse oximetry patents, leading to a trade ban in late 2023. Apple briefly paused U.S. sales of Series 9 and Ultra 2, then disabled the feature via software to keep selling. The iOS 18.6.1 workaround—processing data on the iPhone instead of the watch—lets Apple restore the feature without stepping on Masimo’s patents. It’s a brilliant pivot, though I miss the old-school instant watch readouts.
How to Get iOS 18.6.1 and watchOS 11.6.1
Updating is a breeze:
- iPhone (iOS 18.6.1):
- Open Settings.
- Tap General > Software Update.
- Select iOS 18.6.1 (build 22G90) and hit Download and Install.
- Follow the prompts.
- Apple Watch (watchOS 11.6.1):
- Ensure your watch is at least 50% charged and on Wi-Fi.
- On your iPhone, open the Watch app.
- Go to General > Software Update.
- Tap Install if available.
- Or, on the watch, go to Settings > General > Software Update.
Pro tip: I always plug in my watch before updating—nothing tanks the vibe like a dead battery mid-install. Both updates dropped on August 14, 2025, so check your devices now!
What’s Not in the Update
These releases are all about blood oxygen, with no confirmed extras like new watch faces, UI tweaks, or major bug fixes. Apple’s notes are tight-lipped on anything else, though minor security patches might be hiding under the hood. If you’re craving a bigger overhaul, iOS 19’s preview at WWDC 2025 (June 9) is your next stop.
What’s Next for Apple Watch Health Tech?
This update sets the stage for more health innovations. Apple’s teased blood pressure monitoring for the Series 11, expected in September 2025, and I’m betting WWDC 2025 will bring deeper Health app integrations, maybe tying blood oxygen to fitness goals or sleep tracking. The return of this feature shows Apple’s not backing down, even with legal hurdles. I’m already hyped for what’s next—maybe a glucose monitor one day?
Tips to Rock the Blood Oxygen Feature
Ready to dive in? Here’s my game plan:
- Update Now: Grab iOS 18.6.1 and watchOS 11.6.1 to unlock blood oxygen monitoring.
- Explore the Health App: Check the Respiratory section for your readings and trends—it’s a goldmine for health nerds.
- Test It Out: Try a session after a workout, hike, or even meditation to see how your levels shift. I’m stoked to compare mine pre- and post-run.
- Share with Your Doc: Export your data from the Health app for checkups—it’s a great convo starter.
- Keep It Charged: Avoid update fails by ensuring your watch is juiced up. I learned that lesson after a bricked update years ago.
Wrapping Up: A Health Tech Win Worth Celebrating
The iOS 18.6.1 and watchOS 11.6.1 release on August 14, 2025, is a massive moment for U.S. Apple Watch users, bringing back blood oxygen monitoring for Series 9, Series 10, and Ultra 2. The iPhone-processed, Health app-displayed feature is a slick workaround to a messy patent dispute, proving Apple’s got serious game when it comes to health tech. Whether you’re a gym rat tracking every stat, a hiker curious about altitude effects, or just someone who loves data (hi, that’s me!), this update is a reason to fire up your Settings app and get started.
Head to Software Update on your iPhone, and let your watch join the party. Got plans to test your blood oxygen or thoughts on Apple’s health tech hustle? Drop them in the comments—I’m all ears and ready to geek out!
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