Hypokalaemia is said to have occurred when serum potassium levels are persistently below 3.5mmol/L.

Causes of hypokalaemia

  • Inadequate dietary intake (rare)
  • Gastrointestinal fluid loss (vomiting, diarrhoea, fistulae)
  • Renal loss (diuretics, uncontrolled diabetes mellitus)
  • Systemic metabolic alkalosi
  • Dialysis.

Clinical Features

Clinical features for hypokalaemia include the following:

  • Muscular weakness
  • Tetany
  • Fatigability
  • Thirst
  • Polyuria
  • Paralytic ileus
  • Cardiac arrhythmias
  • Low serum potassium
  • Elevated serum bicarbonate
  • Low serum chloride
  • ST segment depression and appearance of V waves on ECG


  • Urea and electrolytes
  • ECG


  • Treat cause where possible.
  • If necessary give oral potassium (Slow K), 80–100mmol daily or intravenous (at a rate of infusion not to exceed 25mmol/hr).
  • Care must be taken in patients with renal failure to avoid hyperkalaemia.
  • Never give potassium IV as a bolus. The patient will have cardiac arrest.