The best time of day to measure blood pressure is relative. Generally speaking, the blood pressure is most accurate when you first wake up in the morning, before you get up, and the blood pressure measured at this time is closest to the standard blood pressure of basal metabolism. However, 24-hour ambulatory blood pressure monitoring shows that the blood pressure at each time is different, and the blood pressure of normal people shows obvious circadian fluctuations, that is, the blood pressure is lowest at night and rises rapidly after morning activities, while there is a peak at 6-10 a.m. and 4-8 p.m. throughout the day, followed by a slow decline. In daily life, blood pressure increases with activity, a full meal, emotional stress, mental tension or cold. In daily life, insomnia, smoking, alcohol and coffee consumption can also affect the change of blood pressure. Patients with hypertension should ideally monitor their blood pressure at the time of the weakest effect of antihypertensive medication, such as after waking up in the morning, and at the longest time, such as in the evening and before going to bed, while they are taking medication for treatment.