Anemia is a relatively common disease in all of our lives. To be precise, anemia is a symptom rather than a specific disease, and can be associated with various diseases. Anemia is a condition in which the hemoglobin per unit volume of circulating blood is below the lower limit of normal value. The hemoglobin standard for the diagnosis of anemia in China is below 120g/L for adult men, 110g/L for women and 100g/L for pregnant women. The first symptoms of anemia are fatigue, sleepiness, weakness, pale skin, mucous membranes and nails, panic and shortness of breath after activity. Severe and long-term anemia may cause enlarged heart, increased heart rate and pulse rate, low fever, dizziness, headache, tinnitus, blurred vision, lack of concentration, drowsiness, loss of appetite, abdominal distension, nausea and constipation. The reproductive system may show menstrual irregularities in women and loss of libido in both sexes. Anemia can be classified according to the pathogenesis: ①Anemia caused by poor hematopoiesis: e.g., reblindness; ②Anemia caused by excessive destruction of red blood cells: e.g., hereditary spherocytosis; ③Anemia caused by excessive blood loss: e.g., gastrointestinal bleeding caused by ulcers or tumors. 2. According to the cell size pattern, it can be divided into: ① large cell anemia, such as megaloblastic anemia; ② normocytic anemia, such as hemolytic anemia, reocclusion, etc.; ③ simple small cell anemia, such as chronic infectious anemia. ④Small cell hypochromic anemia, such as iron deficiency anemia, etc.