Management of Hypokalaemia (plasma K+ <3.5mmol/L)

Assessment / monitoring

  • Plasma potassium

General management

  • Replace potassium losses
  • Identify and treat underlying cause where possible:
    • Loop / thiazide diuretics - consider combination with a potassium-sparing diuretic
    • Vomiting and diarrhoea
    • Intracellular potassium shifts, e.g. post-operation, coronary ischaemia, critical illness
    • Re-feeding
    • Hypomagnesaemia

N.B. If hypokalaemia remains unexplained, more specialised investigations may be appropriate. Advice may be obtained from your local Biochemistry Department.

Drug therapy / treatment options

General notes

  • Oral potassium chloride is the treatment of choice for most patients. Effervescent tablets (Sando-K®), each contain 12mmol of potassium and 8mmol of chloride.

  • The dosage and duration of treatment depends on existing potassium deficit and whether there is continuing potassium loss.

  • Larger doses may be required especially in patients with digitoxicity or diabetic ketoacidosis. Advice is available from the Biochemistry Department.

  • Potassium supplements should not be given in severe renal impairment or if plasma K+ >5mmol/L.
  • Caution should be used in patients with renal insufficiency or when Angiotensin-Converting Enzyme (ACE) inhibitors or potassium-sparing diuretics are being administered concomitantly.

Suggested starting doses (but see notes above before prescribing)

Oral potassium supplementation

  • For plasma K+ 3-3.5mmol/L (approximate potassium deficit 200mmol): Sando-K® 2 tablets 3 times daily
    • Monitor plasma K+ twice weekly until stable.
    • Once plasma K+ stable or if plasma K+ >4.5mmol/L, reassess requirement for supplementation.
  • Plasma K+ 2.5-2.9mmol/L (approximate potassium deficit 200-400mmol): Sando-K® 3 tablets 3 times daily
    • Monitor plasma K+ daily until plasma K+ >2.9mmol/L and then manage as above.
  • Plasma K+ <2.5mmol/L or cardiac arrhythmia (approximate deficit >400mmol): Intravenous supplementation is usually required.

Intravenous potassium supplementation

  • Intravenous supplements are indicated if patients cannot eat, are unlikely to absorb oral potassium or have profound hypokalaemia.
  • Where possible use pre-prepared infusion bags. These are available as:
    • 20mmol KCI in 500ml sodium chloride 0.9% or glucose 5%
    • 40mmol KCI in 500ml sodium chloride 0.9% or glucose 5%
  • The rate of infusion should not normally exceed 10mmol/hour.
  • 10ml ampoules of strong potassium chloride containing 20mmol potassium per ampoule are only available in intensive care areas and should not be used in ward areas unless in exceptional circumstances and under close supervision. These must be ordered in the controlled drug requisition book.
  • If concentrations other than those mentioned above are required, contact your clinical pharmacist or Medicines Information for advice (see Appendix 6 for contact details).


Guideline reviewed: May 2023

Page last updated: May 2023