A big reason people's first measurement is often high is the positioning while putting the cuff on, adjusting to the pose, and then settling in place, a process which can spike pressure. Ideally you prepare yourself (cuff on, in place with your arms at rest, etc) and sit there and relax for five minutes before you take the first measurement, making it legitimately reflective of the at-rest state.
This often isn't possible, but it's a reason doctor visits usually drop you in a room by yourself with a machine that will take multiple measurements with a lengthy delay between. Though that's where the white coat thing comes into play and people are stressed about a doctor coming in, etc.
This often isn't possible, but it's a reason doctor visits usually drop you in a room by yourself with a machine that will take multiple measurements with a lengthy delay between. Though that's where the white coat thing comes into play and people are stressed about a doctor coming in, etc.