An iron infusion is a preparation of iron delivered through an intravenous line directly into the bloodstream, states the American Society of Hematology. Iron infusions are for people who can't absorb enough iron through their gastrointestinal tract.
Intravenous iron comes in three different preparations: iron dextran, iron sucrose and ferric gluconate, according to the American Society of Hematology. Though an allergic reaction is possible with all three preparations, it occurs more frequently with iron dextran. The benefit of iron dextran is that a patient may receive a high dose at one time, while iron sucrose and ferric gluconate must be spread out in smaller doses over several weeks.