Apple Watch Series 10 Blood Oxygen: 'Unable to analyze

Hngoodman wrote:

Blood Oxygen was measured successfully early this morning while sleeping.

7-9 hours later, tried about 12 manually initiated Blood Oxygen readings on the watch.

Readings appeared to succeed on the watch, but in Apple Health app I am being told “unable to analyze blood oxygen” for every *single* reading.

Tried restarting both phone and watch, problem persists.

Apple Watch Series 10

watchOS version 26.3

iPhone 15 Pro

iOS version 26.3

I think that means that it is getting inconsistent data. The Apple Watch documentation says that a "snug fit" is essential to get good oxygen readings. And: "keep your watch facing up and try not to move. Resting your wrist on a table can help." So I think this means that measurements during sleep, exercise, or even just moving around might not be as suitable or accurate. And it seems sensitive to have the watch fit snugly on the wrist/arm. The documentation also mentions that the watch should "not be too low on the wrist."

I'm not sure what this all means except that it seems like a challenging measurement for the watch. It is shining a light into your arm/wrist and trying to sense the oxygen content. For mine, it seems to show 92%-100% but it is clearly a "noisy" measurement from the scatter in the data. Also, I have had my oxygen readings in clinics (using a finger sensor) while sitting very still and it was always close to or at 100%.

One has to be careful in interpreting data from an Apple Watch because it is intended to provide information on general health, but not serve as a medical device.

Since you are having trouble getting a reading, I would read the guidance from Apple (in the Health app) about oxygen readings and focus some on the fit and snugness and position of the watch. I think the oxygen reading is more delicate and harder to get than the heart rate, which can be achieved during exercise, motion, bumping, jostling, shaking etc. I think the oxygen reading may depend more on the user physiology match to the watch than some of the other measurements.