Apple Watch 6’s blood oxygen sensor is unreliable and misleading – The Washington Post

Sometimes the new Apple Watch Series 6 reports my lungs and heart are the picture of health, pumping blood that’s 100 percent saturated with oxygen.

At other times, it reports my blood oxygen is so low I might be suffering from emphysema. (I am not.)

The watch can’t decide. This much is clear: Don’t buy one of these $400 devices in the hopes of monitoring your lung health.

I’m very skeptical about including a pulse oximeter in a consumer device like this. I don’t know who would need to use this, or when, and the fact that it is not very accurate can make people worry needlessly. As the article points out, this device is not approved by the FDA, and, according to Apple, is “only designed for general fitness and wellness purposes.”

There are important differences in the blood oxygen data that Apple and Fitbit report. But in my experience, neither company’s measurement serves much purpose at all. You should know what you’re buying, because it might do more harm than good.


It should not be acceptable for giant tech companies to market devices that take readings of our bodies without disclosing how those devices were tested and what their error ranges might be.

Source: Apple Watch 6’s blood oxygen sensor is unreliable and misleading – The Washington Post

10 thoughts on “Apple Watch 6’s blood oxygen sensor is unreliable and misleading – The Washington Post

  1. I’ve had my watch 6 nearly a week now and used the blood oximeter 5 times always reporting 95-97%. I have checked it against a standalone device and it has confirmed the readings. If you were low you’d know it, my father in law has breathing issues and as soon as his falls below 85% he suffers. The device I checked my watch against was his. Like most things this type of watch does, it has to be assumed it’s only a guide. My wife’s Fitbit reports many more steps than my watch does, my watch tells me I’ve only climbed 6 or 7 flights of stairs a day when I know I’ve done many more. I think the point is (for me anyway) it makes you take much more interest in your health. The breathing app really does calm me and makes me think about de-stressing. I had my previous Apple Watch since they first came out and loved every minute of using it. I’ve passed it onto my son who uses it for running and also is loving it.

  2. If you live with a neurological disease, as I do, and suffer random interruptions of breathing efficiency, often not noticing until you have a screaming headache and you’ve done incalculable damage to your heart and other cells throughout your body, you will appreciate a device a fraction of the size and cost of a belt-worn or wrist- and finger-worn, bulky, intrusive and anything-but-discreet pulse-oximeter monitor and logging device. I’ve only had my 6 a bit over a week, and like the 4 before it, whose fall detection and ECG have given me more freedom from being tethered to bulky, life-limiting, attention-drawing, extremely-expensive home/“portable” medical equipment (not to mention calling paramedics and my family four times now when I’ve passed out and fallen causing serious injuries); as well as a level of safety and independence no longer requiring expensive CNAs to insure my safety; the Apple Watch has proven to be reliably within 1% of my $2K, 6oz, water-resistant wrist/finger monitor, and doesn’t require doing a wired data-dump and upload to my pulmonologist every 12 hours. It just happens, and all i need do is keep the battery charged, and seek oxygen when it buzzes my wrist and throws an alert.

    The very fact that I can finally, safely, and without supervision of a CNA, jump into a swimming pool and not worry about my wrist going deeper than splash-level; and not drawing the constant curious stares with multiple cyborg devices and sensor wires taped all over my body, is a game changer and literal life changer.

    I’m not going to speak to the WaPo author’s personal experience and disappointment, but your own skepticism and admitted ignorance as to whom will benefit, should be better-tempered and taken with a large dash of salt. So, now, at least you know of one single category of disease that will be tremendously offset by the 6; and my instinct tells me Apple would’ve preferred to wait until it could claim FDA clearance, if not full approval as a device with a given amount of error reliability; but that even without it, it offers tremendous benefits, especially in the time of COVID.

    My only disappointment is that the 6 didn’t also deliver continuous or periodic blood pressure monitoring, so I will continue to have to wear two “wristwatches” for at least another year.

    Happy Monday


    • You’re one of a very small number of people who benefit from this. The problem is that it is simply not accurate. I got my series 6 on Friday, and most of the time, I can’t get a reading. When I could get a reading, it was 91-93%, whereas with a fingertip pulse oximeter I have, it was 97-98% at the same time.

      You may have better results, but it looks like this is much less accurate than the heart rate sensor (which was wildly inaccurate when the watch was first launched, and still has issues for a lot of people).

      • I’m one of tens of millions with my particular disease; and there are tens, if not hundreds of millions of people with COPD, asthma, emphysema, and other disorders, many of whom don’t even know it.

        Just like the cardiac monitoring of the 4, the pulseOx will improve, and improve the health of millions of people. Personally, I think it’s worth a period of needless, unintentional alerts in daily life — especially during sleep — to encourage people to compare the results with a $10 fingertip meter, and show a doctor, too, if the data is anything less than 90% for more than a couple-few minutes. The doctor can order a full-time O₂ study with a medically approved device, if needed.

        In the coming months, you will see many, many more reports of life-saving and health-improving, due to Apple Watch 6 than you did cardiac anecdotes. This is going to show thousands of users who wear it overnight that they have sleep apnea or obstructive breathing issues requiring treatment; thousands of smokers and vapers and unprotected workers in dangerous, polluted environments, that they are killing themselves, slowly and painfully; and more. This device is going to help keep insurance rates and tax dollars spent low, by catching more conditions early, before the lead to severe cardiopulmonary complications and disease.

        I’m sorry it’s not working well yet for some; but, please, take heart that for some of us, who’ve tested it side by side for many days with a medically-approved, prescribed meter, that its accuracy and reliability is possible; the inconsistencies need only be discovered and addressed, by Apple via software, or by the variables of the people wearing them (band type and tightness, position, recognizing vascular deficiencies or skin-density deviations, etc.).

        This device can and will improve the health and lives of a considerable number of humans.

      • I should also mention I get different results on left or right wrist, and very different, more accurate readings on the inside of the wrist. The arm difference is easily explained by vascular differences due to my condition (I get the same variation with a fingertip meter); the inside by the same vascular prominence of the ulnar and radial arteries.

        It still infuriates me, that to this day, Apple still does not provide a usable, fully-functional preference for the inside of the wrist. Military and many industrial occupations require it, and many types of sports and hobbies do, as well. If the pulseOx proves to be more reliable on the inside, perhaps they will finally relent on this maddening issue.

        Cheers — F

          • What doesn’t work properly is, primarily, Raise to Wake. It comes on when your wrist is down (murdering the battery), and turns off when you raise it to see/use it. Maddening. If you’re cool with Theatre Mode, it’s “fine”, but then useless for Hey Siri and just checking the time (on Series 4 and earlier). The always-on display of the 5 and 6 only barely mitigate, as they do not display current complications or workouts (in some apps) until you tap to wake. Sucks when you’re working out, or using equipment/machines at work, or riding a bike/motorcycle, and can’t turn your wrist, when glancing at the inside of the wrist is easiest and most desirable.

            • It’s better in the Series 6 because of the way complications can still display when it’s not raised. And the display is brighter overall: brighter when it’s bright, and brighter when it’s dim. There is also an option to hide “sensitive” complications when it’s not raised.

            • I’m finding that my favorite cardiac monitors and third-party work out complications are not updating when the screen is dim. Hopefully this is something that will improve as developers have time to work on bug reports.

  3. Federico, did you check the Display > Always On > Hide Sensitive Complications setting? It might be on by default.

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