Blood pressure is unstable, fluctuating between 120-150 mmHg, depending on whether the patient exercises or not and whether the blood pressure is measured at different times of the day. The human blood pressure is allowed to fluctuate 24 hours a day under the influence of circadian rhythms. There are two peaks and two troughs in blood pressure throughout the day. The first peak of blood pressure is between 6 and 8 a.m., and after 8 a.m. it begins to fall. However, it remains at a high level after 8:00 a.m. and continues until noon. 12-2:00 a.m. is the first trough of blood pressure throughout the day. From 2 p.m. blood pressure begins to rise, with a second peak from 6-8 p.m. However, this peak is lower than the first peak at 6-8 a.m. Blood pressure continues to fall after 8 p.m., and will drop to the lowest point of the day at 2-3 a.m., the second trough. Therefore, normal people should measure their blood pressure in the early morning, after fasting, urination, and in a quiet state, when the blood pressure is the patient’s basal blood pressure. If the patient exercises vigorously, the blood pressure can temporarily rise to 150 mmHg and gradually fall to 120 mmHg, at which time the patient cannot be diagnosed with hypertension. Blood pressure can be affected by a variety of factors such as body position, emotion, exercise, meals, bowel movements, etc. There are both general patterns and individual differences, so attention should be paid to the time and method of measuring blood pressure.