The highest blood pressure in a normal person is between 6:00 a.m. and 10:00 a.m. There is another peak between 4:00 p.m. and 8:00 p.m., and the blood pressure at night is often the lowest time of the day. However, patients with hypertension tend to lose this pattern, as the blood pressure pattern of normal people belongs to the bimodal and valley type of blood pressure, that is, there are two peak periods and one low period in a day. In patients with hypertension, the peak and trough periods of blood pressure are likely to break this pattern. Therefore, to further assess the patient’s overall blood pressure, it is recommended that the patient bring an ambulatory blood pressure monitor so that the patient’s overall 24-hour blood pressure can be better assessed. For patients with high blood pressure at night, additional antihypertensive medications may be given at night or taken primarily at night. Also, ambulatory blood pressure monitoring is performed to detect hidden hypertension as well as to avoid white coat hypertension.