The best absorbed iron supplement are ferrous sulfate, ferrous fumarate, and ferrous gluconate. Those are ferrous iron salts.

• Nature Made Iron 65mg, Equivalent to 325 mg Ferrous Sulfate - 300 Tablets
• Freeda Ferrous Fumarate Iron 29 mg. - 250 TAB
• Ferrous Gluconate 324 Mg Tablets - 100 Ea