A drop in blood pressure does not necessarily mean that shock will occur. The main cause of shock is due to a sudden decrease in the effective circulating blood volume in the body. A drop in blood pressure is just one of the signs of shock, but not necessarily shock as long as the blood pressure drops. Shock when blood pressure is characterized by a decrease in blood pressure, high pressure less than 90mmHg, the patient appears organ ischemic manifestations, such as fuzzy consciousness, while the pulse pressure difference is reduced, is the most important indicator of shock. There are many reasons for the drop in blood pressure, such as overdose of antihypertensive drugs, poor diet, and as long as the blood pressure is above the normal range, even a drop in blood pressure is not considered shock. The most important thing is to clarify the cause of shock, common causes are bleeding, loss of body fluids, such as diarrhea, cardiogenic shock, infection, etc. If the patient has the above causes, accompanied by changes in blood pressure, high pressure less than 90mmHg, pulse pressure difference less than 20mmHg, must be considered shock.