Blood pressure lower than 90/60mmHg is called hypotension, the reasons are as follows: 1, physiological reasons, characterized by no uncomfortable symptoms, also does not affect work and life, common in some healthy people, thin elderly, women and summer heat. 2, pathological reasons, low blood pressure accompanied by uncomfortable symptoms and disease. It can be divided into acute hypotension and chronic hypotension. Acute hypotension is a sudden and significant drop in blood pressure from normal levels to below 90/60 mmHg, mostly in a state of shock. Common causes include hemorrhage, acute myocardial infarction, severe infection, allergy, etc. Chronic hypotension is a slow onset and gradual aggravation, commonly seen in severe tuberculosis, advanced cancer, severe anemia, malnutrition, cachexia, and long-term dieting and weight loss. In addition, hypotension can occur when the body position is changed from prone or squatting to upright and when certain drugs are applied, such as antihypertensives, diuretics, vasodilators, and antidepressants.