When blood is drawn from a patient and the blood does not flow halfway, there are several common reasons for this: First, the test tube used to draw blood from the patient is blocked or the negative pressure in the test tube disappears, so the test tube or the drainage tube connected to the needle can be replaced to continue drawing blood. Second, the patient’s body is in a state of hypercoagulation, such as hyperlipidemia or thrombosis, when the blood is drawn because of the slow flow of blood, the patient’s blood can coagulate resulting in the inability to draw. It is recommended that the patient be given a large amount of crystals and colloids to reduce the hypercoagulable state of the patient’s blood and then have the blood drawn again. Third, if the patient has lost more blood due to hemorrhagic shock, the peripheral vasculature is in a state of obvious constriction, and the blood in the vessels is gathered in the head, brain, kidneys and other important organs, so the blood cannot really be completely drawn out during the process of blood sampling.