Hypotension can be categorized into acute hypotension and chronic hypotension. Acute hypotension is often due to acute ischemia of the heart, brain, kidneys and other important organs, and patients experience dizziness, blackness in front of the eyes, limb weakness, cold sweating, palpitations, oliguria and other symptoms. Severe acute hypotension can result in fainting or shock or even life-threatening. Chronic low blood pressure includes the following aspects: 1. Constitutional low blood pressure: it is generally believed that constitutional low blood pressure is related to heredity and body weakness and wasting, the light ones do not have any symptom, and the heavy ones have neuropsychiatric symptom, which manifests as fatigue, dizziness, headache and even fainting. Generally, low blood pressure is more obvious in summer when the temperature is high; 2. postural hypotension: within 3 minutes of changing position from recumbent to upright, the systolic blood pressure decreases >20mmHg, or the diastolic blood pressure decreases >10mmHg, accompanied by low perfusion symptoms, including dizziness, headache, blurred vision, nausea, vomiting, cognitive dysfunction, etc., which can be called postural hypotension; 3. secondary hypotension: some diseases or medications can cause hypotension, and some of them can cause low blood pressure. Diseases or drugs can cause hypotension, such as aortic stenosis, mitral stenosis, overdose of antihypertensive drugs and some antidepressant drugs.