Anemia is not the name of a disease, it is a symptom, a common manifestation of many diseases. In terms of diagnosis, the first thing to do is to determine if it is anemia. Instead of thinking that dizziness and weakness and dark eyes are anemia, check if the red blood cell count and hemoglobin amount are lower than normal. If anemia is present, the cause of the anemia should be further examined. Most patients with anemia have dizziness, fatigue, weakness of the limbs, palpitations and shortness of breath, especially after activity. The examination may reveal pallor of the face and mucous membranes, increased heart rate, and heart enlargement if the anemia is chronic. If the anemia is considered to be microcytic hypochromic anemia by erythrocyte, hemoglobin, and erythrocyte pressure product tests, take a medical history and check for internal bleeding, such as gastric or duodenal ulcer disease, gastrointestinal tumors, internal hemorrhoid bleeding, or excessive menstruation in women. The diagnosis of iron deficiency anemia can be confirmed by checking serum ferritin, erythrocyte free protoporphyrin, plasma iron or iron inside and outside the bone marrow cells. If, in addition to anemia, neurological symptoms such as numbness in the hands and feet, unsteadiness in walking, and unresponsiveness are found, and there is a history of partial eating or malnutrition, especially in children older than 1 year old who do not add complementary foods, the patient may have megaloblastic anemia with vitamin B12 or folic acid deficiency, and the bone marrow picture will show typical megaloblastic red blood cells and reduced quantification of vitamin B12 or folic acid. If the anemia is combined with jaundice, the patient may have a pale yellow face, and in severe cases, the urine may become tea-colored, wine-colored, or even soy sauce-colored hemoglobinuria, and sometimes there is mild enlargement of the spleen, which is mostly a hemolytic anemia. If the anemia starts at an early age, and there is a clear family history, an enlarged spleen or a history of eating fava beans or taking various strong oxidants, such as primaquine, it may be congenital hemolytic anemia. In acquired or congenital hemolytic anemia, peripheral blood erythrocytes may be anisotropic, polyphilic, H-J’s vesicles, dotted color or nucleated erythrocytes may be seen, and the erythrocyte system in the bone marrow may be significantly hyperplastic. The diagnosis of hemolysis is only the first step and further in-depth examination should be performed to determine what type of hemolytic anemia is present. Bone marrow examination is an important tool to understand diseases such as aplastic anemia, megaloblastic anemia, leukemia, and bone marrow metastases. Proliferative anemia is only an indication of good bone marrow hematopoiesis but not a determination of the type of anemia.