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I just updated my phone (16 Pro) and watch (Ultra 2 Black). Ran an ECG test, then went to the Blood Oxygen app and it worked perfectly (result 97%, showed up immediately in Health app).

There have been several suggestions in this thread and a similar one to run an ECG test first, then go to the Blood Oxygen app and it will work. Might want to try that.
Just ran EKG. Only showed September 2024 reading. Not looking to unpair and repair. If that’s what I need I’ll just wait a month with Ultra 3.
And there’s no go to the app as it says it’s unavailable.
 

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Just ran EKG. Only showed September 2024 reading. Not looking to unpair and repair. If that’s what I need I’ll just wait a month with Ultra 3.
And there’s no go to the app as it says it’s unavailable.
Did you update both iOS on your phone and WatchOS? Your phone should be on iOS 18.6.1, and your watch should be on 11.6.1. If they're not both updated, or you're using beta software on either of them, that will be the problem.

If they're both updated to the proper versions, try restarting both devices. Also, go into your watch settings and turn on Blood Oxygen recordings (Apple Watch App > Settings > Blood Oxygen > Blood Oxygen Recordings).
 
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Did you update both iOS on your phone and WatchOS? Your phone should be on iOS 18.6.1, and your watch should be on 11.6.1. If they're not both updated, or you're using beta software on either of them, that will be the problem.

If they're both updated to the proper versions, try restarting both devices. Also, go into your watch settings and turn on Blood Oxygen recordings (Apple Watch App > Settings > Blood Oxygen > Blood Oxygen Recordings).
You can’t turn it on in either device. Multiple reboots.
 
So basically Apple DID breach the patent as it has had to change how the feature works to make it legal. Well at least they came up with a workaround. Personally I've never found the feature to be very useful as it is wildly inaccurate anyway.

When you have or know someone who has suffered from multiple pulmonary embolisms (with some of them being in the submassive size), you may find that O2 sensor to be one of the most life saving features a person can have.

My point: Just because you may be in good health and may not see any usefulness of the feature does not mean that someone else doesn't.

I may be wrong but, I don't believe a working sensor would be disabled after a battery replacement.

I've seen a few S9s and even an S8 that had the battery replaced resulting in the O2 sensor being disabled. I was looking at getting a refurb S8 or even S9, but not knowing if the battery was replaced, I stuck with my S7 that is still a workhorse.

BL.
 
There is a rerelease of iOS 26 beta 6 that came out simultaneously with iOS 18.6.1 and watchOS 11.6.1, but I skimmed through the release notes there isn’t any documentation that suggests the SPO2 app comeback.

I look forward to asking watchOS 26 beta testers on my beta thread if they got the updated build on their iPhone and tested if the Blood Oxygen app works again on their Apple Watch Series 9, 10 and ultra 2 models. You can find my linked thread 👇


Also y’all while you guys get your watches and iPhones updated to iOS 18.6.1 and watchOS 11.6.1 respectively, here is a reel I found on YouTube that shows a black Apple Watch Ultra 2 and iPhone 16PM user that demonstrates the (alternative) blood oxygen app comeback:
 
What about my Apple Watch Series 7 replaced by Apple at the Apple Store which was given back to me without Blood Oxygen Enabled? I hope they re-enable those ones too!

** Update: my iPhone is running iOS26 Public Beta 3 and no dice. I updated my Watch which still shows it greyed out and I confirmed its a Watch Serial ending in LW/A as the Apple KB notes.
I guess this means Apple failed to port the same fix into their iOS 26 branch. :(
 
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What about my Apple Watch Series 7 replaced by Apple at the Apple Store which was given back to me without Blood Oxygen Enabled? I hope they re-enable those ones too!

** Update: my iPhone is running iOS26 Public Beta 3 and no dice. I updated my Watch which still shows it greyed out and I confirmed its a Watch Serial ending in LW/A as the Apple KB notes.
I guess this means Apple failed to port the same fix into their iOS 26 branch. :(
I have a Series 6 that was replaced by Apple, which doesn't have the oxygen sensor anymore. After this update and running the ECG app, the oxygen sensor worked again. But of course, I could only see the results on the iPhone and not on the watch.
 
I don’t know what’s wrong with yours, but the blood oxygen sensor on my Ultra 2 and Series 9 both activate in the background and I typically get a new reading every ~2 hours. This was the same on my series 8 and series 7 as well. You do not need to activate it manually to get readings.
Thank you. I dug through the settings and found the issue. I have Theater Mode turned on all the time. The default Blood Oxygen settings is to not take blood oxygen readings while in Theater Mode.

How do you get it to 100? I’ve never gotten it that high on my Apple Watch, and my fingertip pulse ox literally says it only reads to 99%.
I breathed in and out quickly and deeply using my diaphragm. Also, while I was doing this, I was at a hospital hooked up to the hospital’s EKG. My Series 7 was just as accurate as the hospital’s. It was a while ago, but it was at-most 1 off from the hospital’s.
 

I’m running both but I deliberately bought a refurbished S9 with a working blood oxygen sensor last year and a titanium case so I can’t help you there. Mine has always worked in the betas for both.

I may be looking to upgrade the older S7 also with the sensor that I sleep and swim with to an S11 and start using the S9 as my overnight watch if the Milanese Loop that works with my S9 still works with the S11 even if I go with a less expensive material like aluminum versus titanium.

I’m wondering what materials they’ll use for the upper echelon, non-aluminum watch when the S11 comes out. The slate options on the S10 looked nice but I’m partial to titanium which you could get on the S9.

It matches the titanium case on my iPhone 15 Pro but rumor has it that’s going away on the phone, so maybe aluminum with a snazzy loop will be the way to go. We’ll see. Either way I refused to upgrade until this feature returned and though not being able to see it in the watch is kind of a PITA if I can get it in the health app on the phone I can live with that compromise until Massimo realizes they aren’t going to win and either asks for a reasonable license fee or stops beating this dead horse all together and stops trying to enforce it here or worksite deal where Apple and they both settle their suites against each other paving the way for Apple to return the feature to how it used to work in the US and Massimo being able to keep using the designs they gave been sued for by Apple but I won’t be holding my breath on that one.
 
Much as this feature is a nice to have it was hopelessly inaccurate on my Ultra V1 when compared to my own medical equipment quality pulse oximeter and my doctor’s pulse oximeter which both agreed with each other (the watch read around 10 to 15% low). This tends to make me suspicious of a lot of the medical data provided by the watch, although the afib detection does seem to be quite accurate if a little over sensitive. So, glad it is back for those that can use it, but I will continue with my separate measuring device for the moment.
 
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I just updated my phone (16 Pro) and watch (Ultra 2 Black). Ran an ECG test, then went to the Blood Oxygen app and it worked perfectly (result 97%, showed up immediately in Health app).

There have been several suggestions in this thread and a similar one to run an ECG test first, then go to the Blood Oxygen app and it will work. Might want to try that.
I wish I had known that before pairing my watch as new !
 
When you have or know someone who has suffered from multiple pulmonary embolisms (with some of them being in the submassive size), you may find that O2 sensor to be one of the most life saving features a person can have.

My point: Just because you may be in good health and may not see any usefulness of the feature does not mean that someone else doesn't.



I've seen a few S9s and even an S8 that had the battery replaced resulting in the O2 sensor being disabled. I was looking at getting a refurb S8 or even S9, but not knowing if the battery was replaced, I stuck with my S7 that is still a workhorse.

BL.

Sorry but I have seen many people complain that the sensor is not very good. And it should NEVER be used as a reliable medical tool, only as a guide at best. Also I never said I do not see ‘usefulness’ of a the feature, that is you assuming things, also you are again assuming claiming I am in good health, how do you know?
 
It didn't work on Series 7 in the morning but now - it worked with results on iPhone

Who knows, maybe tomorrow they will restore adequate UI on-watch :) or at least on watchOS 26
 
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