Normal blood pressure in humans ranges from 90 to 139 mmHg systolic and 60 to 89 mmHg diastolic. The normal systolic blood pressure range is 90~139mmHg, and the normal diastolic blood pressure range is 60~89mmHg. where systolic blood pressure of 120~139mmHg, and/or diastolic blood pressure of 80~89mmHg belong to the normal high value of blood pressure, which still belongs to the normal range of blood pressure, but has a higher possibility of developing into high blood pressure. Both too high and too low blood pressure are harmful to health. A systolic blood pressure ≥140mmHg and/or a diastolic blood pressure ≥90mmHg three times on a non-same day is considered high blood pressure, which may lead to coronary heart disease, cerebral infarction, cerebral hemorrhage, and so on. <90/60mmHg is considered low blood pressure, which may lead to weakness and fainting. It is recommended that people with abnormal blood pressure should retest their blood pressure on a non-same day and follow medical advice if they suffer from hypertension or hypotension.