How would a watch measure blood pressure and blood oxygen?

I wouldn’t trust it for those two functions either.
Might be fun to check out though, if you are happy enough with the other functions.

Blood pressure is not among the features listed for the watch.

Unless it has a tight band and has some form of automatic tightening it cannot measure blood pressure..That claim is bogus.
However, it theoretically it can measure blood oxygen level and heart rate.

Blood is a very clever material. It changes color depending upon the presence or absence of oxygen. Look at your veins. They are blue because your body used up the oxygen carried in the blood changing its color to blue. That blood is pumped by the heart into the lungs where it is oxygenated again and turns red. That is why your arteries are red. They are filled with freshly oxygenated blood ready to do work.
Now look at that magic green light. Caution: there are different designs so this might not be exactly how your works. That green light is a laser diode or LED that actually emits 2 wavelengths, the green that you see and an infrared that you don’t see. If you look closely and move your eyes around you will see it is also flashing at a high frequency.
By looking at the ratio of the reflected light into the nearby detector it can see the color of your blood. By looking at the rate of change of the absorption it calculates the heart rate.
You can buy pulse oxcimeters for about $20—$30 that work really well.

“Heart Rate Monitoring & Sleep Tracking: Automatically monitor your daily real-time heart rate, and track your sleep quality status to get a better understanding of your health ”

No mention of Oxygen or B/P functions.

My “Bakeey V19” https://www.youtube.com/watch?v=m5gKccIt7Bk blood pressure measurement is pretty precise but not so accurate.

The V19 is consistently a little high for blood pressure arm sphygmomanometer reading this morning was 107/68 and the VP reading was 111/81

The V19 also measures time, O2, heart rate, steps per day, sleep quality and quantity, and an ECG. The ECG is pretty crappy but the other aspects are pretty accurate. How it functions with the green light on the wrist is a mystery to me.

I bought my V19 from eBay for $24 with free shipping.

In the hospital they use a fingertip oxygen reader that also simply shines a light at your skin. It’s definitely a legit way to go.

Regarding heart rate, I have a five year old Fitbit Charge HR which measures with a green LED. It’s pretty accurate when sitting still (I used a stethoscope and watch to test the accuracy).

I was thinking about replacing it in the fall and from what I gather, Letscom is a decent brand, and the $30—$40 fitness trackers are a great buy. I would recommend it over a Fitbit because of the price.

The watch doesn’t say it on Amazon but it is a feature on the watch. I can click and have it measure it. I think it isn’t very accurate, either.

Blood pressure? Interesting.

@gondwanalon How does the watch know when it is at the same level as your heart? Position makes a big difference. It’s a basic hydraulics problem.

@LuckyGuy The person knows if they are in the right position or not. No matter what a person uses to take their blood pressure they need to be aware of their position.

That particular watch you linked to does not measure blood pressure or blood oxygen level.

It is the same one I bought (from my recent orders list) and it does so I am very confused now

Nevermind, I see what I did wrong. I’ll link the one I bought later.