The diagnosis of iron deficiency anemia includes two aspects: one is to establish whether there is anemia caused by iron deficiency, and the other is to clarify the cause of the iron deficiency. First, we need to carefully inquire and analyze the medical history, combined with the patient's physical examination, which can provide a series of clues for diagnosing iron deficiency anemia. A definitive diagnosis also requires laboratory evidence. Clinically, we can divide iron deficiency and iron deficiency anemia into three stages: iron deficiency, iron-deficient erythropoiesis, and iron deficiency anemia. The following describes the diagnostic criteria for iron deficiency anemia specifically. Iron deficiency anemia is characterized by a significant reduction in hemoglobin in red blood cells, presenting as microcytic hypochromic anemia. Its diagnostic basis includes three aspects: first, conforming to the diagnosis of iron deficiency and iron-deficient erythropoiesis; second, having microcytic hypochromic anemia; and third, effective treatment with iron supplements. These three factors together can confirm the diagnosis of this disease.