Apple’s latest update, iOS 18.6.1, has arrived with more than just routine fixes and stability improvements. Unlike many smaller patches, this update is drawing significant attention because it brings back a feature that U.S. Apple Watch users have been missing for a long time — Blood Oxygen monitoring.

iOS 18.6 Problems No One Warned You About—And How to Fix Them Fast

Feature was disabled for American users due to ongoing patent disputes, leaving a noticeable gap in the Apple Watch’s health and wellness ecosystem. With iOS 18.6.1, Apple has introduced a unique solution: moving the processing work from the Watch itself to the iPhone.

This innovative approach not only restores the feature but also highlights Apple’s determination to continue providing its users with health tools, even under complex legal restrictions.

What Is iOS 18.6.1 and Why This Update Matters

The iOS 18.6.1 update, released in mid-August 2025, is a critical update that goes beyond typical behind-the-scenes enhancements. Most incremental iOS releases usually focus on patching security vulnerabilities, smoothing system performance, or eliminating minor bugs. iOS 18.6.1 has become a major talking point because of its direct impact on Apple Watch users.

Those who track their health regularly, the absence of Blood Oxygen monitoring was more than an inconvenience — it was a missing piece of their daily health routine. Apple’s decision to restore this feature demonstrates how seriously the company takes user feedback and how it balances innovation with compliance.

Instead of simply accepting the loss of this feature due to a legal battle, Apple chose to develop an alternative pathway that gives users access once again, which is why this update carries so much weight.

Why Blood Oxygen Monitoring Was Disabled on Apple Watch in the U.S.

Blood Oxygen monitoring, first introduced with the Apple Watch Series 6, became an essential tool for many users interested in monitoring their health and wellness. The feature measured SpO₂ levels, which can provide important insights into breathing, fitness, and overall cardiovascular health. However, Apple found itself embroiled in a legal dispute with a medical technology company that claimed patents related to the feature.

As a result of this ongoing dispute, Apple was forced to disable Blood Oxygen monitoring on Apple Watches sold in the U.S., even though the feature continued to function normally in other markets around the world.

For nearly 18 months, users in America had to make do without one of the most popular Apple Watch health functions. This left many customers frustrated, not only because they lost a valuable health feature but also because it created a sense of inequality between international users and U.S.-based users.

How iOS 18.6.1 Brings Blood Oxygen Monitoring Back

Apple’s solution in iOS 18.6.1 is both clever and practical. Instead of processing Blood Oxygen readings directly on the Apple Watch — which is what triggered the patent dispute — Apple has shifted the responsibility to the iPhone. This small but crucial change allows Apple to reintroduce the feature while staying within the bounds of U.S. legal requirements.

Apple Watch still plays an important role. Its sensors collect the raw data from the user’s wrist, just as they always have. However, instead of processing that data immediately on the Watch, the information is now transmitted securely to the paired iPhone. The iPhone then runs the necessary algorithms, processes the data, and presents the results to the user through the Health app.

This adjustment means the Apple Watch itself is no longer handling the patented processes, allowing the feature to legally return to U.S. devices. For users, the difference is almost invisible — they still wear their Watch, take measurements, and view results, but the behind-the-scenes processing is now happening elsewhere.

Step-by-Step: How to Use Blood Oxygen Monitoring After Updating to iOS 18.6.1

If updating to iOS 18.6.1, here’s how you can start using the restored Blood Oxygen feature:

  • Update Devices: Ensure your iPhone is updated to iOS 18.6.1 and your Apple Watch to the corresponding watchOS 11.6.1.
  • Open the Health App: On your iPhone, launch the Health app where Blood Oxygen readings will now appear.
  • Enable Blood Oxygen Monitoring: Go to Settings > Health > Blood Oxygen and toggle the feature on.
  • Check Your Readings: Measurements will be taken periodically or manually, and results will now be processed on the iPhone instead of the Watch.

    Compatibility is currently supported for Apple Watch Series 6 and later models paired with iPhones capable of running iOS 18.6.1.

    Limitations of Blood Oxygen Tracking on iOS 18.6.1

    While this is a welcome return, users should note a few differences compared to the original experience:

    • Dependence on iPhone: The Watch alone cannot provide full results; it requires the iPhone to process the data.
    • Possible Delays: Since data must travel from Watch to iPhone, readings may take slightly longer to appear.
    • Health Insights: Some detailed metrics that were previously handled on the Watch might now be streamlined or limited due to the shift.

    Although these adjustments exist, for most users the restored access outweighs the trade-offs.

    Performance & Battery Life: Does iOS 18.6.1 Impact Apple Watch or iPhone?

    One concern users often have with updates is whether new processing methods will drain battery life. With iOS 18.6.1, Apple has optimized the system to minimize energy impact. Early feedback suggests:

    • Apple Watch Battery: Since calculations are no longer done on the Watch, its battery consumption may actually improve slightly.
    • iPhone Battery: While the iPhone now handles more data processing, the impact on battery appears minimal due to Apple’s efficient algorithms.

    Overall, the update strikes a good balance between functionality and performance without significant drawbacks.

    Other Fixes and Features in iOS 18.6.1

    Though the headline feature is Blood Oxygen monitoring, iOS 18.6.1 also includes several additional improvements:

    • Security patches to address vulnerabilities.
    • Bug fixes for system stability.
    • Performance optimizations across apps and system processes.

    While Apple didn’t advertise any major new features beyond the health update, these refinements make iOS 18.6.1 a worthwhile download for all users.

    For now, the iPhone-based solution in iOS 18.6.1 is likely to remain the standard. Apple has proven it can adapt quickly, and if legal restrictions ease, the feature may shift back to the Watch in the future. Until then, users can enjoy having access to a feature they were forced to live without.

    FAQs

    1. What is iOS 18.6.1?

    Apple released iOS 18.6.1 in August 2025 as an important software update for iPhones. Unlike smaller patches that only fix bugs or enhance security, this update restores Blood Oxygen monitoring for Apple Watch users in the U.S. Apple designed iOS 18.6.1 to bypass the legal restrictions that previously disabled this feature, making it one of the most significant iOS updates of the year.

    2. How does iOS 18.6.1 restore Blood Oxygen monitoring on Apple Watch?

    With iOS 18.6.1, Apple shifted the responsibility of processing Blood Oxygen data from the Watch to the iPhone. The Apple Watch sensors still collect raw SpO₂ data, but the paired iPhone now performs the calculations and displays results in the Health app. This change allows Apple to legally restore the feature while keeping the user experience almost the same as before.

    3. Which Apple Watch models support Blood Oxygen monitoring after iOS 18.6.1?

    You can use Blood Oxygen monitoring with iOS 18.6.1 if you own an Apple Watch Series 6 or later. These models contain the necessary hardware sensors to capture SpO₂ data. Older models, such as the Series 5 or earlier, do not support this feature because they lack compatible sensors, even if you update your iPhone to iOS 18.6.1.

    4. Do I need to update both my iPhone and Apple Watch for Blood Oxygen to work?

    Yes, you need to update both devices. Install iOS 18.6.1 on your iPhone and watchOS 11.6.1 on your Apple Watch. The Watch collects the data, but the iPhone processes it, so both devices must run the latest software to restore Blood Oxygen monitoring. Without these updates, the feature will not work.

    5. Is Blood Oxygen monitoring accurate with iOS 18.6.1?

    Yes, iOS 18.6.1 maintains accurate Blood Oxygen measurements. The Apple Watch still gathers raw data using its advanced sensors, and the iPhone performs calculations with Apple’s trusted algorithms. Since Apple only shifted the processing location, not the data collection method, users can continue relying on the accuracy of their Blood Oxygen readings.

    6. Does iOS 18.6.1 affect Apple Watch or iPhone battery life?

    iOS 18.6.1 slightly improves Apple Watch battery life because the Watch no longer handles the intensive calculations. The iPhone now performs this task, but Apple optimized the process to minimize energy use. Early reports confirm that iPhone battery performance remains steady after the update, so users can update without worrying about major battery drain.

    7. Can I use Blood Oxygen monitoring without my iPhone nearby?

    No, you cannot. With iOS 18.6.1, the iPhone processes all Blood Oxygen calculations. If your iPhone is not nearby, the Apple Watch cannot complete the reading. This limitation means you must keep your iPhone within range whenever you want to use the Blood Oxygen feature.

    8. Why did Apple disable Blood Oxygen monitoring in the U.S. before iOS 18.6.1?

    Apple disabled Blood Oxygen monitoring in the U.S. due to a patent dispute with a medical technology company. The company claimed that Apple’s method of processing SpO₂ data infringed on its intellectual property. To comply with court rulings, Apple removed the feature from U.S. devices. With iOS 18.6.1, Apple found a legal workaround by moving the processing to the iPhone, making the feature available again.

    9. What other improvements come with iOS 18.6.1?

    Besides restoring Blood Oxygen monitoring, Apple included several improvements in iOS 18.6.1. The update fixes system bugs that previously caused glitches, improves performance across apps, and adds essential security patches. These upgrades ensure iPhones remain stable, secure, and efficient, making the update valuable even for users who do not rely on Blood Oxygen tracking.

    10. Should I install iOS 18.6.1 right now?

    Yes, you should install iOS 18.6.1 as soon as possible. Apple Watch users benefit most because the update restores Blood Oxygen monitoring, but all iPhone users gain from stronger security and smoother performance. Since early reports show no major issues with the update, downloading iOS 18.6.1 right away helps you stay protected and enjoy the new feature immediately.