Blood pressure can drop for many reasons, such as the effect of drugs, overuse of antihypertensive drugs or insufficient effective blood volume, and internal bleeding. If the bleeding is large and cannot be stopped or transfused in time, thus causing insufficient blood perfusion to the body tissues, which leads to cellular hypoxia causing dilatation of peripheral blood vessels and a sharp decrease in effective blood volume, seriously affecting the blood supply to vital organs such as the heart, brain and kidneys. Other causes are myocardial infarction, severe infection, trauma, and allergy, all of which may cause a drop in blood pressure. Postural drop in blood pressure is seen in weak and sickly people with poor regulation of vegetative nerve function. Urinary blood pressure drop is caused by sudden emptying of the bladder, a sudden drop in abdominal pressure, and a sudden decrease in the amount of blood returned to the heart. Blood pressure drop can cause serious clinical manifestations such as dizziness, panic, sweating, blackness in front of the eyes, and sudden collapse, which should be treated promptly.