[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Conditions](https://durgical.com/en/conditions/) › Hypokalaemia [Conditions](https://durgical.com/en/conditions/) · [Metabolism (biochemistry)](https://durgical.com/en/conditions/) # Hypokalaemia Blood potassium is low, usually from diuretics, vomiting or diarrhoea; it causes weakness and arrhythmias. Updated 2026-11-01 ## Structures involved Tap one to see what it is and open it in 3D. - [Kidneys](https://durgical.com/en/anatomy/kidney/) - [Left adrenal gland](https://durgical.com/en/anatomy/suprarenal-gland/) - [Right adrenal gland](https://durgical.com/en/anatomy/suprarenal-gland-abdomen/) - [Ileum](https://durgical.com/en/anatomy/ileum/) - [Sinoatrial (SA) node](https://durgical.com/en/anatomy/sinuatrial-node/) - [Atrioventricular (AV) node](https://durgical.com/en/anatomy/atrioventricular-node/) ## In embryology - [Hypertrophic pyloric stenosis](https://durgical.com/en/embryology/hypertrophic-pyloric-stenosis/) ## In physiology - [How arrhythmias arise](https://durgical.com/en/physiology/how-arrhythmias-arise/) - [The ECG in potassium and calcium disorders](https://durgical.com/en/physiology/the-ecg-in-potassium-and-calcium-disorders/) - [The resting membrane potential](https://durgical.com/en/physiology/the-resting-membrane-potential/) - [The Nernst and Goldman equations](https://durgical.com/en/physiology/the-nernst-and-goldman-equations/) - [Primary and secondary active transport](https://durgical.com/en/physiology/primary-and-secondary-active-transport/) - [Aldosterone: actions and control](https://durgical.com/en/physiology/aldosterone-actions-and-control/) - [Islets and insulin: secretion and actions](https://durgical.com/en/physiology/islets-and-insulin-secretion-and-actions/) - [Water and electrolyte absorption and how diarrhea happens](https://durgical.com/en/physiology/water-and-electrolyte-absorption-and-how-diarrhea-happens/) - [Vomiting and its control](https://durgical.com/en/physiology/vomiting-and-its-control/) - [Prolonged fasting and starvation](https://durgical.com/en/physiology/prolonged-fasting-and-starvation/) - [Refractory periods and excitability](https://durgical.com/en/physiology/refractory-periods-and-excitability/) - [Transport in the loop of Henle](https://durgical.com/en/physiology/transport-in-the-loop-of-henle/) - [Distal tubule and collecting duct](https://durgical.com/en/physiology/distal-tubule-and-collecting-duct/) - [Potassium balance](https://durgical.com/en/physiology/potassium-balance/) - [Reasoning through fluid and electrolyte imbalances](https://durgical.com/en/physiology/reasoning-through-fluid-and-electrolyte-imbalances/) - [Where and how diuretics act](https://durgical.com/en/physiology/where-and-how-diuretics-act/) - [Renal handling of H⁺ and bicarbonate](https://durgical.com/en/physiology/renal-handling-of-h-and-bicarbonate/) - [Metabolic alkalosis and its compensation](https://durgical.com/en/physiology/metabolic-alkalosis-and-its-compensation/) - [Renal handling of calcium, phosphate and magnesium](https://durgical.com/en/physiology/renal-handling-of-calcium-phosphate-and-magnesium/) ## Why it happens - [Cachexia, anorexia nervosa and bulimia](https://durgical.com/en/general-pathology/cachexia-anorexia-nervosa-and-bulimia/) ## What it is A low serum potassium from renal or gut losses, a shift of potassium into cells or, rarely, poor intake. ## Who gets it It is common in hospital patients and people taking diuretics; acute diarrhoea often causes it in Latin American children. ## Causes - Renal loss: loop and thiazide diuretics, hyperaldosteronism, Cushing, Bartter and Gitelman syndromes, RTA types 1 and 2, hypomagnesaemia, amphotericin B - Gut loss: diarrhoea, laxatives, fistulas, villous adenoma; vomiting acts mainly through renal loss secondary to alkalosis - Shift into cells: insulin, β2 agonists (salbutamol), alkalosis, refeeding, hypokalaemic periodic paralysis (thyrotoxic or familial) - Very low intake: anorexia, alcoholism ## Risk factors - Diuretic use - Prolonged vomiting or diarrhoea - Insulin treatment of ketoacidosis - Laxative misuse or eating disorders - Hypertension with aldosteronism ## Pathophysiology 98 % of potassium is inside cells, held there by Na⁺/K⁺-ATPase; the gradient sets the resting potential. With low extracellular potassium the membrane hyperpolarises and repolarisation is prolonged: muscle weakness, ileus, cramps, rhabdomyolysis and, in the heart, U waves, flattened T waves, long QT and arrhythmias (more so with digoxin). In the [kidney](https://durgical.com/en/anatomy/kidney/), hypokalaemia increases ammonium production and bicarbonate reabsorption (sustaining alkalosis) and causes ADH resistance (polyuria). Hypomagnesaemia increases renal potassium loss through ROMK channels, so it must be corrected. ## Classification - By mechanism: shift, renal loss (high urine potassium), extrarenal loss (low urine potassium) - By severity: mild, moderate, severe by the laboratory and symptoms ## Symptoms and signs - Muscle weakness and fatigue - Cramps and muscle pain - Constipation or ileus - Palpitations - Polyuria - Paralysis when severe ## Red flags - Arrhythmias or ECG changes - Weakness affecting breathing - Patient on digoxin - Hypokalaemia during ketoacidosis treatment ## Diagnosis **Clinical** Review drugs (diuretics, insulin, salbutamol, laxatives), gut losses and blood pressure. **Tests** Serum potassium, magnesium, arterial gases (alkalosis or acidosis), urine potassium or urine potassium/creatinine ratio, renin and aldosterone if hypertensive, ECG. **Imaging** Adrenal CT if primary hyperaldosteronism is confirmed. ## Treatment **Medical** Oral potassium replacement when mild or moderate without severe symptoms **Medical** Intravenous potassium with cardiac monitoring when severe or with arrhythmias, within each protocol's rate limits **Medical** Correct magnesium and treat the cause (adjust diuretics, potassium-sparing agents, treat aldosteronism) **Follow-up** Serial potassium and ECG checks ## Complications - Ventricular arrhythmias - Paralysis and respiratory failure - Rhabdomyolysis - Paralytic ileus - Chronic hypokalaemic nephropathy ## Prognosis Good once the cause is corrected; severe hypokalaemia in heart disease raises the risk of sudden death. ## Prevention - Monitoring potassium on diuretics - Replacing potassium in ketoacidosis before insulin drives it down - Replacing fluids and electrolytes in diarrhoea ## Test yourself Think of the answer, then tap the question to see it. ## Which ECG findings does hypokalaemia produce? Flattened T waves, U waves, ST depression and long QT, with a risk of arrhythmias. ## Why does insulin lower potassium? It activates Na⁺/K⁺-ATPase and drives potassium into cells. ## Why must magnesium be corrected in hypokalaemia? Hypomagnesaemia increases renal potassium secretion and makes hypokalaemia resistant to replacement. ## How does vomiting cause hypokalaemia when gastric juice holds little potassium? Through alkalosis and volume depletion, which activate aldosterone and increase renal potassium loss. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/conditions/hypokalaemia/) ## Related conditions - [Metabolic alkalosis](https://durgical.com/en/conditions/metabolic-alkalosis/) - [Refeeding syndrome](https://durgical.com/en/conditions/refeeding-syndrome/) - [Hyperkalaemia](https://durgical.com/en/conditions/hyperkalaemia/) - [Acute (viral) gastroenteritis](https://durgical.com/en/conditions/acute-gastroenteritis/) - [Diabetic ketoacidosis](https://durgical.com/en/conditions/diabetic-ketoacidosis/) - [Cushing syndrome](https://durgical.com/en/conditions/cushing-syndrome/) Educational information, not medical advice. For any symptom, see a health professional. Sources: [Low blood potassium: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/000479.htm) (MedlinePlus, US National Library of Medicine, 2026); [Potassium Blood Test: MedlinePlus Medical Test](https://medlineplus.gov/lab-tests/potassium-blood-test/) (MedlinePlus, US National Library of Medicine, 2026); [Magnesium Blood Test: MedlinePlus Medical Test](https://medlineplus.gov/lab-tests/magnesium-blood-test/) (MedlinePlus, US National Library of Medicine, 2026); Textbook of Biochemistry for Medical Students, 6th ed. (Jaypee Brothers Medical Publishers (Vasudevan DM, Sreekumari S, Vaidyanathan K), 2011). [← All conditions](https://durgical.com/en/conditions/) ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. 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