For a long time I've noticed that if I take my blood pressure a second time, the readings vary especially for the systolic reading. If I don't like the reading, I just take it again (recording both).
I wonder if these expected variances are known.
As an example, this morning I made the following three readings, one after the other, without readjusting the cuff on my left arm on a Medline brand of home blood pressure monitor:
SYS 119 DIA 79 Pulse 83 SYS 105 DIA 76 Pulse 79 SYS 109 DIA 75 Pulse 79
I would have expected the readings to differ no more than plus or minus 2, but perhaps what I am getting are normal variances.
This is from the comments:
- I think the key point here is that BP is used as a trend, and a rough idea. If your BP is always <120 and >100, the exact range doesn’t matter because as Carey said, BP itself changes rapidly, and the measurement methods (even manually) have limited accuracy. If you‘d want to be as accurate as possible, it’s probably best to measure twice, once left and once right. This not only gives you an estimation of the error bar, but if your BP constantly varies between l&r (i.e. right is always +20mmHg), it is also a sign that something is wrong (Thanks to @Narusan)