Low serum iron generally suggests that moderate deficiency of iron in the body may cause symptoms such as low appetite and irritability, while severe deficiency can cause iron deficiency anemia. 1. Moderate deficiency. Organism iron deficiency generally only appear ferritin reduction, this time no obvious symptoms; and low serum iron is generally moderate deficiency, can affect hemoglobin synthesis, but not yet appeared anemia, can appear low appetite, children are prone to irritability, adults are prone to apathy; and children under 2 years old may affect cognitive ability, infancy may lead to neurodevelopmental damage. 2. Severe deficiency. Iron deficiency anemia will occur, there may be weakness, dizziness, palpitations (rapid heartbeat, often accompanied by panic) and other symptoms, and children may have stunted growth and reduced concentration. When the body is deficient in iron, it should be supplemented under the guidance of a doctor.