Ferric carboxymaltose (Ferinject®) is an infusion administered for the treatment of iron deficiency anaemia. A number of previous case reports have shown the occurrence of hypophosphataemia after Ferinject® treatment, supposedly managed though high dose phosphate therapy. This case report highlights the risk associated with, and futility of, managing this adverse effect through high dose phosphate infusion. A review of the available literature suggests that if hypophosphataemia develops as a result of Ferinject®, through upregulation of the renal protein Fibroblast Growth Factor-23, it cannot be readily reversed and on average persists for circa 50 days. Acute medical units should be aware of this – likely underreported – adverse effect, and avoid treating these hypophosphataemic patients with high dose phosphate since it can compound symptoms.

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