Blood pressure fluctuates at different times of the day, with two peaks and two troughs in a 24-hour period, and there is a circadian rhythm. The first peak in blood pressure occurs between 6-10 am. A second peak in blood pressure can occur between 4-6 pm. Some patients present with a predominantly nocturnal increase in blood pressure. The patient’s blood pressure can be understood through 24-hour blood pressure monitoring. To obtain an accurate blood pressure measurement, the patient needs to sit still for at least 5 min before the blood pressure measurement. The patient’s blood pressure is usually measured in a sitting position with the blood pressure cuff at the same level as the heart. Bilateral upper extremity blood pressure should be measured for the first time, preferably more than 2 times, to help detect aortic arch narrowing and upper extremity arterial occlusion; when there is a persistent difference between left and right upper arm blood pressure, the upper arm blood pressure of the side with the higher blood pressure should prevail.