You will need to wear a blood pressure cuff for 24 hours.
It's connected to a small, portable measuring device that automatically measures your blood pressure at set times and records the readings.
Ambulatory blood pressure monitoring is used, for example, to see whether blood pressure levels vary greatly over the course of the day and night or whether they are constantly elevated.
During those 24 hours, you can do all of the usual things you would otherwise do over the course of the day.
If you are especially active at certain times, you can make a note in a diary.
Then the doctor has a better idea of how to interpret the recorded values when evaluating them.