In children, iron deficiency anemia is a common childhood blood disorder. How to determine if a child has iron deficiency anemia is usually done by first looking at a routine blood test sheet. In a routine blood test, we can see a decrease in hemoglobin, a decrease in mean red blood cell volume (MCV), and a decrease in mean red blood cell hemoglobin (MCH), which we call microcytic anemia; in more severe iron deficiency anemia, we can also see a decrease in mean red blood cell hemoglobin concentration (MCHC), which we call microcytic hypochromic anemia, but sometimes we see a decrease in hemoglobin, a decrease in MCHC, and a decrease in MCHC. However, sometimes we see a decrease in hemoglobin, a decrease in mean erythrocyte volume and a decrease in mean erythrocyte hemoglobin, etc. It is not yet possible to determine whether a child has iron deficiency anemia, because another common anemia in children (thalassemia) also presents as microcytic anemia (or microcytic hypochromic anemia). Therefore, to determine if a child has iron deficiency anemia, it is recommended to check serum ferritin and serum iron, etc. If a decrease in serum ferritin and serum iron is found, it can generally be determined that the child has iron deficiency anemia. However, sometimes the disease is more complicated, or to further clarify whether the child is suffering from iron deficiency anemia, bone marrow examination can be performed, and if there is iron deficiency in the bone marrow, the diagnosis of iron deficiency anemia will be more clear.