It is normal for normal people to have high blood pressure during the day and low blood pressure at night, mainly because of the action of sympathetic and parasympathetic nerves. During the daytime, the sympathetic nerves are excited, the heart rate is accelerated, and the heart contraction is increased, resulting in higher than usual blood pressure, while at night, the vagus nerves are excited, the heart rate is slowed, and lower blood pressure occurs. However, the above situation is only for normal people, even if the blood pressure of normal people is elevated, it should be within the normal range, i.e. high pressure in the range of 90-140 mmHg and low pressure in the range of 60-90 mmHg, if it is higher than this range, it is elevated blood pressure. Therefore, it is normal if the blood pressure is higher during the day than at night, but when it is higher than the normal range, it is elevated. The presence of hypertension should be suspected at this time, and hypertension should be diagnosed when blood pressure is measured higher than normal at least twice on non-same days. Therefore, when blood pressure is high during the day and low at night, the normal value of blood pressure should be clarified first, and if it is within the normal range, it may not be treated, but if hypertension exists, antihypertensive drugs should be given to lower blood pressure.