The causes of anemia can be divided into decreased erythropoiesis and excessive destruction or loss of red blood cells, which can be seen in iron deficiency anemia, renal insufficiency, leukemia, autoimmune hemolysis and other diseases. 1. Iron deficiency anemia and megaloblastic anemia are caused by the lack of hematopoietic raw materials such as iron, vitamin B₁₂, and folic acid, leading to a decrease in erythropoiesis, which leads to the occurrence of anemia. 2. Anemia caused by chronic renal insufficiency, malignant tumors (gastric cancer, lung cancer, etc.) and other diseases is caused by reduced erythropoiesis due to impaired utilization of iron by the body. 3. Anemia caused by leukemia, myeloma, lymphoma, aplastic anemia, myelofibrosis and myelodysplastic syndrome and other hematologic diseases, which is caused by the inhibition of hematopoiesis in the red line of the bone marrow, leading to the reduction of red blood cell production. 4. Anemia caused by autoimmune hemolytic anemia, paroxysmal sleep hemoglobinuria, hereditary spherocytosis, thalassemia, etc. is caused by increased destruction of red blood cells. Anemia patients need to go to the hematology department in a timely manner to improve the relevant examination to clarify the cause of anemia, and then for the cause of the disease under the guidance of physicians for treatment.