The body’s iron reserves are like a reservoir, to ensure a certain amount of reserves to meet the needs of the body’s metabolism. The amount of iron in and out every day should be kept in dynamic balance for the reserve to reach a steady-state level. Too little in such as long-term vegetarianism, gastrointestinal diseases, digestive and absorption disorders, or too much out such as long-term chronic blood loss: bleeding hemorrhoids, bleeding ulcers, excessive menstruation, can cause an imbalance in iron metabolism. After oral medication for iron supplementation, eventually the iron reserve should be replenished. The iron that is started to be taken orally is immediately put into the production line, which is used in priority to make hemoglobin in red blood cells and improve the oxygen-carrying capacity of red blood cells, which may be stored only after there is a surplus. The hemoglobin concentration rises after 2 weeks of iron supplementation therapy and generally returns to normal in about 2 months. Iron therapy continues for at least 4 to 6 months after the hemoglobin returns to normal, and is discontinued when the ferritin is normal. This is why iron supplementation therapy should be continued for six months. At the time of discontinuation, it is recommended to monitor serum ferritin greater than 30-50ug/L.