The formed elements in the blood include red blood cells, white blood cells, and platelets, which play important roles in cellular metabolism, defense, and hemostasis, respectively. Among them, anemia falls under the category of red blood cell diseases. Iron-deficiency anemia refers to a condition where the body's iron stores are depleted, failing to meet the needs for normal red blood cell production. Before the production of red blood cells is restricted, the body's iron stores are already depleted, but anemia has not yet occurred, a condition we call iron deficiency, also known as the subclinical iron deficiency period clinically. Iron-deficiency anemia is a common red blood cell disease and falls under the category of hematology. Therefore, patients with iron-deficiency anemia should consult a specialist in hematology.