Iron deficiency can cause anemia, but iron deficiency is not the same as anemia, because iron deficiency causes anemia through three processes in the body. The first process is called iron deficiency, which means that the concentration of iron in the body’s serum is lower than normal. The second process is iron deficiency erythrocyte formation. At this time, the patient’s hemoglobin is normal. The third stage is called iron deficiency anemia, which is due to the depletion of ferritin in the body before the patient has symptoms of iron deficiency anemia, so iron deficiency does not necessarily lead to symptoms of anemia. However, if iron is deficient for a long time and is constantly depleted without timely replenishment, iron deficiency anemia will definitely occur in the end. Therefore, in clinical practice, some patients’ iron and serum iron are not reduced, but the patient shows symptoms of mild fatigue and weakness, and then it must be noted that the patient is likely to have iron deficiency anemia.