Ferritin is a protein inside of cells that stores iron for later use by your body. The small amount of ferritin that is released into blood reflects the total amount of storage iron. Iron is also stored as hemosiderin, a complex of iron, proteins, and other materials. Ferritin and hemosiderin are present primarily in the liver but also in the bone marrow, spleen, and skeletal muscles. In healthy people, most iron is stored as ferritin (an estimated 70% in men and 80% in women) and smaller amounts are stored as hemosiderin.