Guidance / Documentation on iOS 18.6.1 Blood Oxygen Saturation

Question

Created Aug ’25

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Are there any HealthKit related changes to be aware of in the new update that enables SPO2 / Blood Oxygen Saturation measurements on certain Apple Watch models within the US?

I’m aware of processing happening on the phone…. But beyond that:

Does this mean values are then saved to Apple Health?
Do these models still take background SPO2 measurements in the same way as other models do?
Are these values then visible in third party iOS apps as normal through HealthKit?
Do these values sync back to the paired Apple Watch HealthKit store for third party apps to access on the Watch?

For reference I have an iOS and WatchOS app that, amongst other features, provides the ability to see your SPO2 values in the Watch app, complications and in the iOS app.

Answered by DTS Engineer in 854622022

The oxygen saturation data will be written to the Health store on the iPhone, but will NOT be synchronized to the paired Apple Watch. Apps can access the data using HealthKit APIs (.oxygenSaturation). If you see otherwise, please share here.

I'm unclear the measurement approach part. Hopefully folks who know the detail can jump in.

Best,
——
Ziqiao Chen
 Worldwide Developer Relations.

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Answer 1

DTS Engineer OP

Apple

Aug ’25

Recommended

The oxygen saturation data will be written to the Health store on the iPhone, but will NOT be synchronized to the paired Apple Watch. Apps can access the data using HealthKit APIs (.oxygenSaturation). If you see otherwise, please share here.

I'm unclear the measurement approach part. Hopefully folks who know the detail can jump in.

Best,
——
Ziqiao Chen
 Worldwide Developer Relations.

0

Answer 2

simonfromhelix OP

Aug ’25

Hi Ziqiao,

Thank you for the response on this.

All your first paragraph points sound good. Unfortunately I too don't have an affected device so short of importing one, I'm not sure on the exact behaviour.

As for the measurements, yes any further details you can provide would be good including if the background measurements are still taken in the same way on these models and if data can be automatically synced back to iPhone and therefore the HealthKit database when the iPhone is available.

Thank you

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Answer 3

simonfromhelix OP

1w

Any updates on this? @DTS Engineer

Thanks

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Answer 4

simonfromhelix OP

4d

Going back to my original questions I think I have some answers forming:

Yes, SPO2 values are saved to Apple Health on iPhone
Yes, background measurements are now taken in the same way
Yes, the data is visible through the HealthKit APIs on iPhone only - not directly on Apple Watch
No, HealthKit does not sync these values back to the Apple Watch Health Store

Does this mean I'd have to use frameworks like WatchConnectivity to pass SPO2 data back to my Watch app?

Am I allowed to do that as seemingly Apple Health isn't?

Is there a better approach given the user's iPhone is most likely locked when using their Apple Watch and so the Health store on iPhone is unavailable?

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Answer 5

DTS Engineer OP

Apple

22h

Thanks @simonfromhelix for your following up and update. I'd like to confirm that, in the case you describe, the calculations and measurements are on iPhone, and the data is not synchronized to the watch.

Since the HealthKit store on the watch doesn't have the data, yes, you will need to manage to transfer the data with your own code, and Watch Connectivity is a choice.

Best,
——
Ziqiao Chen
 Worldwide Developer Relations.

0