Iron is an essential nutrient for life, and it is also toxic when in excess. Because humans cannot control the secretion of excess iron from the body, systemic iron homeostasis is maintained by the coordinated regulation of dietary iron absorption in the duodenum, iron recycling from senescent erythrocytes in macrophages, and mobilization of stored iron in the liver. Dysregulation of these processes causes iron overload disorders or iron-restricted anemia (ie, iron-resistant iron deficiency anemia).