Ferritin is an iron

Ferritin is an iron binding protein as opposed to the inorganic iron which is usually used in iron supplements. It is rapidly absorbed & free of the gastrointestinal side effects frequently found with other iron products. Ferritin does not promote oxidation to the extent of the inorganic irons, nor does it deplete antioxidant defenses.*
Iron is a structural component of hemoglobin which carries oxygen to every cell in your body. About 70% of your total body iron is present as hemoglobin, 3% is present in your muscles as myoglobin, & the rest is found in ferritin which, together with hemosiderin, forms the major storage sources of iron.