Anemia is a syndrome that occurs when the body’s peripheral blood red blood cell volume decreases below the lower limit of the normal range and is unable to adequately supply oxygen to tissues and organs. Clinically, a hemoglobin concentration of 30-59 g/L is often considered severe anemia, and a hemoglobin concentration of 30 g/L or less is considered very severe anemia. For patients with severe anemia, the common symptoms and consequences are as follows: 1. Nervous system: Patients may experience headache, dizziness, memory loss, insomnia and even fainting, etc., and may also be complicated by intracranial or fundus bleeding, which may affect intellectual development; 2. Respiratory system: For patients with severe anemia, symptoms such as shortness of breath and shortness of breath may occur even in a calm state, and some of the primary diseases of anemia can also affect the respiratory system If the anemia is caused by leukemia, it can trigger the infiltration of respiratory system. If the anemia is caused by lupus erythematosus, it can be complicated by acute lupus pneumonia. If anemic patients have long-term repeated blood transfusion, it can lead to pulmonary iron-containing hemoglobin deposition; 3. Circulatory system: In severe anemia, patients can easily develop tachycardia. Usually, the more severe the anemia is, the greater the activity, the corresponding increase in heart load and the more obvious the discomfort symptoms will be. In patients with long-term anemia, the heart is undersupplied and overloaded for a long time, which may lead to anemic heart disease, abnormal heart structure, and even cardiac insufficiency. 4. Urinary system: The renal tubules in patients with severe anemia are easily blocked by free hemoglobin, which may lead to oliguria, anuria, and acute renal failure. For patients with acute severe hemorrhagic anemia, there may also be reduced renal blood flow and insufficient blood volume, which may lead to abnormal kidney function if it lasts too long; 5. Skin and hair: Due to the reduced content of red blood cells and hemoglobin in the body, the blood supply to the skin muscle layer is reduced, which leads to symptoms such as dull, pale and rough skin, and in severe cases, ulcers may also be formed. Hair may appear dry and fall out, nails are thin, brittle and easily cracked, and in severe cases, flattened and sunken nails, called spatulate nails. Therefore, patients with severe anemia must be treated promptly by high iron diet, iron supplementation or even blood transfusion as well as surgery, while controlling the primary disease, otherwise severe anemia may progress to very severe anemia and death of the patient may occur.