Following the Masimo patent ruling (court link), Apple disabled Blood Oxygen measurements on U.S. versions of the Apple Watch Series 9, Series 10 and Ultra 2.
Now, thanks to a clever iPhone-side software workaround, users can re-enable the sensor and access the full Blood Oxygen app again — without buying new hardware.
Here’s how to turn it back on:
✅ Step 1: Update Your iPhone
Make sure your paired iPhone is running the latest version of iOS (Settings → General → Software Update).
✅ Step 2: Update Your Apple Watch
On the Watch, go to Settings → General → Software Update and install the latest version of watchOS.
✅ Step 3: Restart Both Devices
Once both updates are installed, reboot the iPhone and the Watch to activate the new workaround logic.
✅ Step 4: Reopen the Blood Oxygen App on Your Watch
On the Watch, find and open the Blood Oxygen app.
If successful, you should see the sensor UI and measurement button again.
✅ Step 5: Enable Measurements in Watch Settings
Still not seeing it? Go to:
Watch Settings → Privacy & Security → Health → Blood Oxygen Measurements
and toggle the Blood Oxygen switch on.
⚠️ Troubleshooting (U.S. Units Only)
| Issue | Fix |
|---|---|
| Blood Oxygen toggle not visible | Unpair and re-pair the Watch to your iPhone |
| “Not available in your region” popup | Force close app → Reopen after iPhone restart |
| Works outside of U.S. but not in U.S. | The workaround may still be rolling out regionally—try again in 24–48h |
Tip: Unpairing / restoring forces the iPhone to rebuild the health feature set and often triggers the new workaround.
Thanks to a smart workaround that offloads part of the blood oxygen calculation to your iPhone, Apple has restored this key health feature on Series 9, Series 10 and Ultra 2 — even in the U.S.
Make sure both devices are fully updated, and the feature should reappear without needing new hardware.
Stay on the latest iOS + watchOS versions to keep access going forward.