Hypokalaemia (low potassium), is a common problem. It is found in 14% of outpatients and 20% of inpatients, however only 4-5% of those are of clinical significance.


  • Severe: <2.5 mEq/l OR Symptomatic – Look for Hypomagnesaemia
  • Moderate: 2.5-2.9 mEq/l (No or Minor symptoms)
  • Mild: 3.0-3.4 mEq/l  (Usually asymptomatic)


  • Cardiac: CCF, Predisposition to DIGOXIN toxicity
    • ECG Changes: Flattened T waves, U waves, ST depression, prominent P (II, III, aVF), Long QT, Wide QRS
    • Arrhythmia: Ectopics (atrial/vent), Sinus Bradycardia, Tachycardia, AV Block, Torsades, VT, VF
  • CNS: Depression, Coma
  • Endocrine: Glucose intolerance
  • GIT: Anorexia, Constipation, intestinal paralysis
  • Neuro-Muscular: Cramps, Weakness, Paraethesia, Tetany, Rhabdomyolysis
  • Renal: Acidosis, Nephropathy
  • Resp: Respiratory failure


1. Replace

  • Severe: IV KCl 40mmol & check Magnesium (often also low)
  • Moderate: Oral potassium replacement – 72mmol/day (2 sando K, TDS) – Monitoring Daily
  • Mild: Oral potassium replacement – 48mmol/day (2 sando K, BD) – Monitor twice weekly

***Renal Impairment: Cautious potassium replacement (medical input advised)***

IV therapy – Severe/unable to tolerate oral replacement

  • Rate: Standard rate 10mmol/hr [maximum 20mmol/hr]
  • Monitoring: Continuous ECG monitoring
  • Hypomagnesaemia: Often a concurrent problem, consider treating with IV magnesium (1-2g over 20min)

Oral therapy

  • Water: Patients should take 100-250ml water with medication (constipation & gastric irritation)
  • Monitoring:  The recommendation come from the UKMi/SPS,
    • Moderate – Daily potassium monitoring, this will need to be arranged either through AAU or by direct contact with GP (i.e. phoning them directly to arrange, as the practicalities for GP’s are likely difficult but may be possible).
    • Mild – Twice Weekly potassium monitoring, this should be arranged through GP. However, the patient will need to arrange this themselves with the GP (as the GP is unlikely to have received and read your discharge letter in time to arrange)

2. Treat the Cause

These need to be thought about and corrected if possible in ED. However, ongoing investigation and management will be through inpatient team or GP.

  • GIT: Vomiting, Diarrhoea, Laxative abuse, Clay
  • Renal: Cushing’s, Conn’s,Hypomagnesemia, Bartter’s, Gitelman’s, Renal tubular acidosis
  • Endocrine: Thyrotoxicosis, Insulin excess/administration
  • Drugs: Salbutamol, Insulin, Diuretics (loop/thiazide/osmotic), Laxitives, Penicillin(high dose)

PDF: Society of Endocrinology Guideline

PDF: UK Medicines information -How is hypokalaemia treated in adults?

Search: hypokalemia, low K

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