Iron deficiency, absolute or functional, is a common pathology in elderly patients and the way of iron replacement therapy is a recurrent issue. It seems to be necessary to treat by intravenous iron instead of oral therapy because of defective iron absorption or side effects. Depending on the molecule chosen, the modes of administration, whether dilution, dose or rhythm, vary. The major risk of intravenous iron replacement is anaphylaxis, which is very rare, this is why it has to be an hospital administration.