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Refeeding syndrome phosphate shift — MRCPCH TAS MCQ

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HardNutrition and metabolismRefeeding syndrome phosphate shiftMRCPCH TAS

A severely malnourished adolescent starts high-calorie feeding and develops weakness, oedema and arrhythmia. Bloods show phosphate 0.32 mmol/L and low potassium. What is the most likely mechanism?

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

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Correct answer: E — Insulin-driven intracellular electrolyte shift

Refeeding syndrome occurs when carbohydrate intake triggers insulin release, shifting phosphate, potassium and magnesium into cells. Vitamin D excess does not explain the acute electrolyte collapse after refeeding. The pearl is that phosphate is essential for ATP production, so rapid falls can cause cardiac and respiratory failure.

Reference: Nelson Textbook of Pediatrics; RCPCH Theory examination syllabi; NICE nutrition support principles