The causes of anemia are more numerous and the mechanisms are more complicated, and the common causes are as follows: 1. hemorrhagic anemia: such as excessive menstruation and gastrointestinal bleeding; 2. hemolytic anemia: that is, anemia caused by the destruction of red blood cells, and hemolysis leads to anemia for a number of reasons, such as extravascular and intravascular reasons as well as reasons related to immunity and infections; 3. bone marrow reasons: anemia due to the obstacle of hematopoiesis in the bone marrow, such as a variety of diseases that originate in the Diseases of the bone marrow can lead to anemia. Bone marrow is the main organ of hematopoiesis, if the patient is malnourished, lack of iron, lack of folic acid or vitamin B, the bone marrow will lead to ineffective hematopoiesis. Therefore, if anemia is found, we should look for the causes from the above three aspects, clarify whether the patient has a history of chronic blood loss, and determine whether the patient has acute hemolysis by acute jaundice, anemia, elevated reticulocytes, and elevated lactate dehydrogenase. Although the pathogenesis of different anemias is different, patients have similar symptoms, such as dizziness, fatigue, poor appetite, panic, and chest tightness. Patients with moderate-to-severe anemia need early intervention and treatment, so once anemia is detected, early consultation is needed to determine the cause through the doctor’s examination, and targeted treatment is the right choice.