Iron deficiency anemia is a common problem worldwide, and doctors of all specialties need to be competent in its treatment. While most patients respond well to oral iron preparations, a substantial minority have side effects that make them adhere poorly to their treatment. For oral iron‑intolerant patients, those responding poorly despite good adherence, and those with severe and/or symptomatic anemia, intravenous iron is an excellent alternative. It is, however, more expensive and carries a very small but potentially life‑threatening risk of severe infusion‑related hypersensitivity reactions. After outlining the main features of iron metabolism, in this review we compare the indications for therapy with oral and intravenous iron, and then focus on how to maximize the efficacy and safety of the two different routes.