The blood in the body is pushed through the closed circulatory system of the heart and blood vessels as the heart systolic and diastolic. The lateral pressure exerted on the walls of the blood vessels as it flows through them is called blood pressure. The ideal blood pressure for adults is <120/80 mm Hg, and the normal range is <140-90/90-60 mm Hg. There can be a mild difference in blood pressure between the two upper extremities, with the average person having a higher blood pressure in the right upper arm than in the left upper arm. If there is a large difference between the blood pressure of the two upper arms, the blood pressure of the higher side should be used to diagnose hypertension and assess the outcome. The lower extremity blood pressure is higher than the upper extremity blood pressure, which should be noted for people who have unfortunately lost their upper arm, and the normal value of blood pressure is about 10 mm Hg higher than the upper extremity. Pulse pressure is the difference between systolic and diastolic blood pressure, and is normally 30-40 mm Hg. Increased pulse pressure is an indicator of atherosclerosis. Both for healthy people and hypertensive patients, blood pressure has a circadian rhythm. During the day, the body is more active, the body needs more oxygen and nutrients, and accordingly requires a large amount of blood to transport, the blood pressure is higher. At night, when the body requires minimal oxygen and nutrients during sleep, blood pressure is lower. In most people, the blood pressure rhythm of 24h a day is that it rises gradually in the morning as they wake up and remains high during the day; at night, it falls gradually to a minimum during sleep, with a nadir at 1~3pm. Changes in season and ambient temperature can cause blood pressure to fluctuate, with blood pressure levels being somewhat higher in winter than in summer. Blood pressure can also rise due to activities such as exercise, excretion, eating and emotional changes such as excitement, stress, anger, anxiety and depression. A healthy person with a temporary increase in blood pressure will recover quickly; if a chronic state of persistently high blood pressure occurs, it becomes hypertension. Normal adults should have their blood pressure measured at least once every six months in order to detect hypertension in a timely manner.