Blood Oxygen - a Disappointment

I received my Apple Watch Series 6 yesterday. Of course one of the first things I tried was the blood oxygen app. The first time I did it, my blood oxygen level was at 84%. Looking online that’s dangerously low. I normally like to wear my watch loosely and lower down my wrist. So I moved it up higher and made the strap tighter and my next reading was 99%.

Throughout the day the readings were hard to get. My most frequent response is Unsuccessful Measurement. I really have to make it tight and sit my arm on a table to have any hope of getting a measurement. I have hairy arms, so I’m wondering if this is making it hard for the light sensor to penetrate.

I love the rest of the watch though. I’m upgrading from Series 4 and I love the always on display. The new watch faces are also fun. The Artist face is surprisingly captivating.

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One way to know for sure :wink:


How about turning the watch to the underside of your wrist while measuring 02.
Vains are very close to the surface and most people don’t have hair on the bottom of their wrists below the palm…

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This is a really great suggestion, I’d be interested to know if people see differences in their measurements depending on the position of which the watch is sitting on the wrist.

With your “vain” typo you’re risking a “I tried that in vein” response. :slight_smile:


Nice idea, but that was even worse. It took about 6 tries before I got a measurement and then it was 90%. I flipped it back around and it measured 97%.

Funny, but no thanks.

Sorry English is my 4th langiage


I have a Series 3 and blood oxygen measurements would be one of the few additional features that would tempt me to move to a new one. I don’t care about hand-wash tracking/measuring. :smiley:

I’m especially interested in VO2 max measuring…if it isn’t reliable I’ll stick to the Series 3.

Even my old Series 2 can estimate VO2 max, but a real VO2 max test requires equipment to measure the percent O2 you breathe in and out, your heart rate, etc. while you run on a treadmill. Most places will charge you at least $100 - $150 the last time I checked.

I mean, the Series 6 has the new “blood oxygenation sensor” and if that isn’t a significant improvement compared to the estimation, no need to upgrade. The “real” test is a hassle.

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It isn’t picking up oxygen from veins…:man_facepalming:.veins carry de-oxygenated blood

A blood oxygen monitor picks up capillary blood. Conventially this has been so on the finger or ear.

I am not sure how this works but I would imagine if you have cold peripheries, or if the watch is loose it doesn’t work that well

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Would anyone else be willing to share this view of their data from Health? Just curious what others get as far as variance. These are all background readings and the average matches my historical results from a finger-clip reader.

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I’d say - mostly - the important thing is to establish your “normal” range. (Which is what you’re doing.)

But I would admit to being a little freaked out to see a 88% - nail I realise it’s a measurement issue in all likelihood.

Sadly it won’t be possible to actually measure this by any watch with any precision or confidence that would make the value somewhat useful.

You’re VO2max is a systemic capability. The current way of measuring it by analyzing the gases you inhale/exhale during a proper cardiac stress test and it will treat your entire body as a black box. The O2 in and CO2 out is measured, while the ergometric stressors are increasing. This allows to get your VO2max for your entire body-“system”. It therefore implicitly includes many factors, such as lung volume, the lung’s breathing capacity or gas exchange capacity, the efficiency of your oxygen transport pathways, the oxygen utilization in your active muscles and those that are necessary for your body to function (heart etc.).

Any kind of value provided by any current app that tries to extrapolate from one’s heart rate changes during an activity increase or any optical sensor-based local (forearm etc.) measurement won’t suffice.
From my personal experience in coaching athletes in competitive performance sports I can tell you that those devices providing “values” should be treated as gimmicks. They are off by magnitudes of +/- 30%. At best they can provide a rough trend or direction if at all given the inaccuracy.

If at all only pay attention to the averages (blue line) over a long time frame. You’re blood oxygen levels vary a lot during the day.

If you are curious: Get one of those cheap finger clip ones, hold your breath while it’s on and observe. Also doing some heavy deep breathing can make it spike up by up to 10%. Observe the measurement when you are walking and talking or walking and eating (climbing stairs after a metro ride, while on the phone or eating breakfast) and you’ll see the value plummet.
Or just find a stair case, hold you breath and walk up :slight_smile:

I’d only be worried if you can’t recover from it in under a minute. If—given you are decently fit and healthy—you feel impacted by shortness of breath a lot in your day to day life than something might not be right.

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What is the line on your screen and how did you get it on?

Here’s mine very up and down for me.

Thank you! I will go through that exercise. I wouldn’t describe myself as healthy overall (diabetic, plus heart disease in family.) If something is wrong I want to know.

When viewing Blood Oxygen, tap Show More Blood Oxygen Data, then tap Daily Average below the graph to turn on the line.

Interesting; thank you! Yours seems a bit more consistent than mine (or, as has been suggested, I’m dealing with a bit of real variance.)

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I have done VO2max tests when I did more sports in the past. Today, I don’t need an accurate figure, I’d be OK with a “good ballpark” that shows me how my aerobic/anaerobic capability is developing. Certainly the watch won’t measure air intake/outtake. I know (and see) that after running my standard running for several weeks that times get better and/or heart rate is lower. Maybe calling it “VO2max” is wrong, but a good graph/chart generate out of running speed+heart rate will correlate to improving VO2 max. Call this value “estimated VO2 max”. Now the question is, and I am completely aware a professional athlete will requiere better testing (I used to train with powermeters on the cycle), is this estimation usable or crap? Useable for somebody who runs 3-4 times a week and just wants to look at improving fitess.