The causes of low blood pressure are atherosclerosis, severe anemia or physiology, and the hazards are ischemia of brain tissue, myocardial ischemia, and renal ischemia. 1.Causes: (1) atherosclerosis: low pressure, the most common cause of low pressure is atherosclerosis in the elderly, when the condition is more serious, due to the stiffness of the walls of the large arteries, the elasticity is reduced, when the heart contraction stops, the large arteries need to be elastic back to push the blood to continue to move forward, which produces a side pressure on the blood vessel wall is the diastolic pressure. (2) Severe anemia or physiological period: low pressure can be seen in severe anemia, or young and middle-aged women physiological hypotension. If it is severe anemia can also be caused by the low pressure. 2.Harms: (1) Cerebral ischemia: If the ischemic state of the brain persists, it can make the patient suffer from cerebral atrophy, headache, dizziness, reduced visual acuity, memory loss, insomnia and sleeplessness, etc.; in serious cases, mental retardation or even dementia can also occur. (2) Myocardial ischemia: Early symptoms are mild and not easy to notice, then with the prolongation of ischemia, patients may have chest tightness, shortness of breath, fatigue, fatigue, etc., and in severe cases, it may also induce acute heart failure, which may jeopardize the patients’ lives. (3) Renal ischemia: there may be no abnormal performance in the early stage, but with the progress of the disease, it may lead to flank pain or abdominal pain, accompanied by oliguria, anuria and even renal failure. If you find that your low blood pressure is low, you should consult a doctor in time to clarify the cause of the disease and give targeted treatment.