When anemia reaches a severe degree or above, the patient is prone to fainting, that is, when the hemoglobin concentration is lower than 60g/L, fainting will easily occur. Especially when the patient goes from a lying position to a standing position or stands up after a long squat, if the standing speed is too fast, it will easily cause a transient lack of blood and oxygen supply to the brain, which will easily cause syncope. There are various clinical causes of severe anemia, the common ones are aplastic anemia, severe iron deficiency anemia, hemolytic anemia and leukemia. In case of severe anemia, the most effective treatment is blood transfusion, which can rapidly increase the number of red blood cells and hemoglobin concentration, and improve the patient’s anemia symptoms. At the same time, patients with severe anemia must move slowly when moving from the prone position to the standing position to avoid fainting and falling down.