The observation of the presence of anemia is generally based on whether the blood count of red blood cells as well as the hemoglobin level is within the normal range. If the hemoglobin concentration is below the low normal limit, it is generally considered to be anemia. If anemia is found, the cause of the anemia should be further examined, first of all, to see if there is a combination of white blood cell and platelet abnormalities on the routine blood count, in addition to the lowered hemoglobin. If there is a combination of leukocyte and platelet abnormalities, bone marrow aspiration is usually required to rule out anemia caused by hematologic diseases, such as aplastic anemia and acute leukemia. If only hemoglobin is decreased in the routine blood test, and white blood cells and platelets are normal, you need to check the anemia triad to observe the levels of ferritin, folic acid and vitamin B12 to determine whether it is a malnutrition anemia. In addition, liver function should be checked to observe whether the bilirubin index is elevated. If the bilirubin is elevated and the hemoglobin is decreased, it may be hemolytic anemia.