What Is Ferrous Fumarate? Ferrous fumarate is a type of iron. You normally get iron from the foods you eat. In your body, iron becomes a part of your hemoglobin (HEEM o glo bin) and myoglobin (MY o glo bin). Hemoglobin carries oxygen through your blood to tissues and organs. Myoglobin helps your muscle cells store oxygen. Molecular formula: C4H2FeO4 Molecular …