The amount of blood drawn should be evaluated according to the patient’s examination items and the severity of the disease: First, if the patient needs routine blood tests and blood biochemistry tests for routine physical examinations. In this case, 2 test tubes are needed for blood sampling, generally about 20 ml of blood should be drawn; second, if the patient performs routine reexamination after surgery, such as after gallbladder surgery and thyroid surgery, only one index check such as thyroid function and liver function should be performed, and 1 test tube should be used, and the amount of blood drawn should be about 10 ml; third, for patients with massive bleeding resulting in hemorrhagic shock, blood sampling should be performed before transfusion Check blood, blood type, coagulation function, blood routine and other indicators. Multiple test tubes are needed to draw blood, and this situation requires about 30-40ml of blood draw.