Most of the iron in the diet is in the ferric (Fe3+) form. It is actively absorbed in:

Gastric secretions dissolve the dietary iron and permit it to form soluble complexes with ascorbic acid and other substances that aid its reduction to the Fe2+ form. Almost all iron absorption occurs in the duodenum. Transpo of Fe2+ into the enterocytes occurs divalent metal transpoer 1 (DMT1). Ref: Barrett K.E., Barman S.M., Boitano S., Brooks H.L. (2012). Chapter 26. Digestion, Absorption, & Nutritional Principles. In K.E. Barrett, S.M. Barman, S. Boitano, H.L. Brooks (Eds), Ganong's Review of Medical Physiology, 24e.