Severe anemia means that the concentration of hemoglobin in peripheral blood is less than 60g/L. After severe anemia, all the tissues of the body will suffer from severe ischemia and hypoxia, which will cause a wide range of effects. Severe anemia can cause the following diseases: a. After severe anemia, due to the increased burden of cardiopulmonary function, heartbeat and respiratory acceleration, over time, due to the compensatory increase in the heart will appear in the volume of the heart, cardiac function decline, clinically known as anemic heart disease, if anemic heart disease is severe, even if the anemia is improved, the heart will not be reduced in size, and there is a chronic cardiac insufficiency. The situation is the same as that of anemia. Secondly, after severe anemia, due to the reduced blood supply to the gastrointestinal tract, the digestive ability decreases, abdominal bloating, diarrhea, constipation and other symptoms of indigestion, but also a decrease in appetite, which can easily lead to severe malnutrition in a long period of time.