In subacute infective endocarditis, if blood culture is done, the volume of blood collected from the specimen is usually 10-15 ml. that is, 10-15 ml of venous blood is collected for blood culture. There are some considerations in the process of collection: the first needle syringe test tube and anticoagulant, there must be a good choice. Then there is the requirement for specimens to be isolated from the air and blood culture specimens to prevent contamination. For some other ones, such as biochemical specimens should be fasted. For drawing different kinds of blood specimens at the same time, the general order of injection containers is the culture bottle of blood, anticoagulation tube, etc. For blood cultures done for subacute infective endocarditis, attention must be paid to strict asepsis, and the volume of blood drawn is 10-15 ml.