Pulse oximeter accuracy

Whilst the 245 doesn't do readings 24/7, you are able to perform manual readings any time by selecting the SPO2 widget as you scroll thru the default widget screens. If the SPO2 widget screen is left for a moment (couple of seconds without pressing any further buttons), it will inform you to stay still as it performs a reading and give you a result which will remain on widget screen until you perform another SPO2 test. No idea what it does with the manual results. 

I too am curious about the validity of the results. According to authoritative medical web sites, healthy is defined as approx 94 and up. During sleep mine fluctuate between 98 and 80, with avg nightly pulse ox of 90. Whenever I have performed a manual reading, has always been in the low 90's. I may be dying...slowly. Maybe not :) Ill take the readings with a pinch of salt as I expect the results mean more to the backend data processing centers than it means to me.

Also as stated up above Garmin says 245 records 4 hours in middle of sleep window. However, my sleep window between 9pm and 7am and I get pulse ox readings/graph for the entire night's sleep, weather I sleep 5 hours or 8 hours (continuous readings, not estimation).

The best way to measure spo2 would be your fingertips, so the pulse reading will not be perfect. No watch will be. It serves only as a reference.

This is inaccurate, mine shows between 83% and 89% during sleeping and between 90 and 95% most of the time during awake. but medical oximeter shows between 97 and 99, I am using vivoactive 4 ,recently purchased

I have been freaking out about my low readings. I need to see my doctor regarding this. My daytime readings using my FR 245 are between 87 - 91, and my sleep readings are mid 80s. This is super unnerving.

FWIW, our household has both a 245 and vivoactive 4. When I wear both devices, they report 100% / 93% respectively, similar for my wife (we've tested them on the same arm, different arms, etc). Thus, I wouldn't trust the numbers much at all; there seems to be a huge margin of error just dependent on the device.

I have a new Garmin Fenix 6 Pro and my readings have been between 92 and 94 most of the first week I happen to go to the doctor for something else yesterday and my finger pulse ox was 98 while my watch was showing 95% so I think these Garmin watches are probably 5% low. I did take my pulse ox with the watch while laying down and keeping my arm level with my chest and the readings went up to 97% — 99%. Hope that helps

Not super accurate.  Just did a finger PulseOx, which was 99, while my Forerunner 235 was 89!

I don't know but I see values ranging from 97% to 100%

Garmin needs to up its game on pulse ox readings. Mine, too, are typically low (my health stats are similar to yours except I'm 65) Was in hospital in July after bike accident. They had me on an oximeter machine (finger reader) so I took the opportunity to simultaneously compare it to my Fenix 6S Pro watch. The watch read three points lower -- 98 vs 95. So I mentally add three now. Garmin should fix its algorithm.