Technical Abstract: The objectives of this study were to compare iron availability from commercial preparations of FeSO4, ferrous gluconate, ferrous fumarate and a polysaccharide-iron complex using an in vitro digestion/Caco-2 cell culture model. Also, we sought to determine if phosphate binding agents (calcium carbonate and calcium acetate) inhibited iron availability from an oral iron supplement when digested simultaneously. Caco-2 cell ferritin formation following exposure to simulated gastric and intestinal digests of the iron supplements was used as a measure of iron uptake and availability. Plates without cell monolayers were included in each replication of the experiment in order to measure the total amount of soluble iron which resulted from the in vitro digestion. Significantly more iron was taken up from the FeSO4, ferrous gluconate and ferrous fumarate relative to the polysaccharide-iron complex. Similar results comparing FeSO4 and the polysaccharide-iron complex have been observed in humans. Also, less iro was taken up from digests with calcium carbonate relative to calcium acetate even though similar amounts of soluble iron were observed in these experiments. The results indicate that when iron supplements and phosphate binders are consumed simultaneously, calcium acetate may be the preferred phosphate binder in order to maximize iron availability.