How is oral phosphate replacement dosed?

Mild hypophosphataemia (serum P 1-2.5 mg/dL): 1-5 mg/kg/day in divided doses. Sodium/potassium phosphate tablets (Neutra-Phos, K-Phos): 250 mg/packet TID-QID is typical.

When is IV phosphate replacement needed?

Severe hypophosphataemia (< 1 mg/dL) or symptomatic (muscle weakness, haemolytic anaemia, respiratory failure, rhabdomyolysis) requires IV phosphate: 0.08-0.16 mmol/kg IV over 6 h.

What causes refeeding hypophosphataemia?

Carbohydrate refeeding in malnourished patients shifts phosphate intracellularly (insulin-mediated). Serum phosphate can drop precipitously, causing respiratory failure, cardiac arrhythmias, and neuromuscular dysfunction.

Phosphate Deficit Estimation Calculator

Estimate phosphate deficit and oral replacement dose for hypophosphataemia. Mild (1-2.5 mg/dL): 1-5 mg/kg/day oral. Severe (< 1 mg/dL): IV replacement required.

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