skip to main content

IV Iron Hypophosphataemia — ESENeph MCQ

Instant feedback + full explanation. One question, done properly.

HardElectrolyte DisordersIV Iron HypophosphataemiaESENeph

A 45-year-old man develops severe hypophosphataemia (phosphate 0.3 mmol/L) after IV iron infusion with Ferric Carboxymaltose. His FGF23 is markedly elevated. What is the mechanism?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: C — FGF23-mediated renal phosphate wasting induced by certain IV iron preparations

Ferric Carboxymaltose (FCM) and some other IV iron preparations can cause hypophosphataemia through FGF23-mediated renal phosphate wasting. FCM inhibits cleavage of intact FGF23, leading to elevated biologically active FGF23, which promotes renal phosphate excretion. This can persist for weeks. Ferric Derisomaltose (Monoferric) has a lower risk. Monitoring phosphate is recommended after FCM, particularly in patients with CKD or nutritional deficiencies.

Reference: Wolf et al 2020 – IV Iron and Hypophosphataemia; BNF 2024