[gaetgu]

This is an interesting point. I know for sure that I have been taught in school to never trust the electronic BP machines, since they can be pretty far off for some (but not all) people.

Instead, using a sphygmomanometer is much more likely to give accurate results.

Anecdotally, I always have a super weird initial blood pressure reading when I go to the doctor and they use the electric machine (one time it was 112/95), but when it is rechecked with a sphygmomanometer it tends to level out at somewhere around 130/85.

[hedora]

If you have a portable meter, you can always take it to the doctor and do a back-to-back or simultaneous reading.

You will probably find that your blood pressure varies more over a 10 minute window than the difference in readings between the two meters.

[jaclaz]

The way a manual sphigmomanometer works is different from the way the electronic ones do[1], I would not be surprised if for a few people something else affects the reading of the pressure in the arm band.

[1] Oscillometric vs. Auscultatory, JFYI:

https://news.ycombinator.com/item?id=36550719