“Do not use the measurement in the doctor’s office.”
I do as you suggest and take my BP at home for the week prior to an exam.
They call this, ‘White Coat Syndrome’ and many people are so psyched about a doctor appointment that your blood pressure DOES rise!
When mine was first recorded as high, I refused all meds, other than a water pill. At the time when mine was high, I had just sold my beloved farm, moved to a bigger farm with more work, my Dad was dying from cancer and we were in the throes of CovidBS-19.
Yeah - no wonder why my blood pressure was elevated! Yeesh!
I’m at normal levels now that my life has evened out again.
The current theory on White Coat effects is not nerves or stress.
It is that as a child, in a medical place, you had some bad experience. Your brain was still developing and this event hard-wired the brain to fight-or-flight in medical environments. You can tell yourself to relax all you want. The hard wiring won’t care.