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April 15th, 2020
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Hypophosphataemia refers to a reduced serum phosphate concentration of <0.8 mmol/L. This may occur in the context of reduced intake, compartmental shift or increased excretion of phosphate.


  • Causes of Hypophosphataemia

  • Reduced Intake / Uptake

  • Severe malnutrition - starvation, alcoholism, anorexia, TPN
  • Malabsorption
  • Vitamin D deficiency
  • Phosphate binders (CKD patients)
  • Antacids
  • Compartmental shift

  • Insulin - recovery post DKA, refeeding syndrome, insulin infusion, glucose infusion
  • Severe respiratory alkalosis
  • Hungry bone syndrome
  • Increased excretion

  • Hyperparathyroidism
  • Vitamin D deficiency
  • Diuretics - acetazolamide, thiazides, loop diuretics
  • Osmotic diuresis (e.g. poorly controlled diabetes)
  • Iron infusion
  • Post renal transplant
  • Fanconi syndrome


  • Signs and Symptoms

    Generally asymptomatic except for in severe hypophosphataemia.
  • Anorexia
  • Lethargy
  • Muscle weakness
  • Seizures
  • Coma
If the cause is not apparent, urinary phosphate (either 24-hour urine or fractional excretion) may be useful in differentiating increased excretion from other causes.
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