Blood donation causes a substantial loss of storage iron. Each unit of blood drawn from a man contains 236 mg of iron or 6% of the total iron stored in the body. Corresponding values for women are 213 mg of iron and 9% (1). An inverse correlation exists between the size of body iron stores and absorbed iron (2-4). As body iron stores decrease, iron absorption increases. With continued iron loss, an individual either reaches equilibrium at a lower concentration of iron stores or becomes iron-depleted, eventually developing iron-deficient erythropoiesis and anemia.