Modern IV iron formulations are extremely safe.
Serious hypersensitivity reactions are exceedingly rare—estimated at fewer than 1 per 200,000 infusions, with no fatalities reported for current low-molecular-weight or non-dextran products. The discontinuation of high-molecular-weight iron dextran (the older, high-risk formulation) has dramatically improved the safety profile of IV iron therapy.
The vast majority of reactions seen today are mild, transient events—typically brief flushing, warmth, chest or back pressure, or anxiety (so-called Fishbane reactions). These occur in roughly 1–3% of infusions, resolve within minutes when the infusion is paused, and do not represent allergy.
Modern pharmacovigilance studies and meta-analyses confirm that IV iron is among the safest parenteral therapies used in clinical practice, with a risk of serious reaction comparable to or lower than that of many routine intravenous medications.
In short: With current formulations and proper infusion technique, IV iron is both safe and well-tolerated. Most patients complete treatment uneventfully, and true anaphylaxis is vanishingly rare.