Please register or login to view the chart

Hypokalaemia- Low potassium

Hypokalaemia is serum potassium concentration of less than 3.5 mmol/ L. Mild hypokalemia is a K+ level of 3.0 to 3.4 mmol/ L. Moderate is 2.5 to 2.9 mmol/L and severe is > 2.5 mmol/L
Causes – redistribution in cells. Acid-base metabolic acidosis
Hormonal -Insulin ( ↑↑ K+ entry into cells ) Beta 2 adrenergic agonists Alpha adrenergic antagonists. Anabolic state -Vitamin B12 or folic acid therapy ( ↑ RBC prod’n ) Granulocyte-
macrophage colony stimulating factor ( WBC production ) Total parenteral nutrition. Other – Pseudo-hypokalaemia Hyperthermia Hypokalaemic periodic paralysis Thyrotoxic periodic paralysis Barium toxicity
dietary –Low intake ( eg starvation , anorexia , old-tea & toast diet )
Daily minimum requirement is considered to be ~ 1600 to 2000 mg
 ( 40-50 mmol or mEq )
Drugs –Amphotericin B Beta agonists Diuretics ( particularly thiazide ) Glucocorticoids ( at high doses ) or mineralocorticoids Aminoglycosides Lithium Insulin overdose Verapamil intoxication Xanthines Decongestants Laxatives
Skin loss –Excessive perspiration
 ( strenous exercise , severe heat stress )
gastrointestinal loss –Vomiting or NG loss Diarrhoe or laxative abuse Ostomy losses Villous adenoma VIPoma
Others – ↑ ed mineralocorticoid activity 
♦ hyperaldosteronism 1ary and 2ary
♦ Cushing’s
♦ congenital adrenal hyperplasia
♦ Bartter’s , Gitelman’s synd Renal tubular acidosis 
( type 1 and 2 ) Salt wasting nephropathy Polyuria Hypomagnesemia
History -assessment –Full history Focus on medications ( eg diuretics , laxatives etc ) Associated symptoms ( eg diarrhoea ) Examination- flaccid muscle weakness , arrythmia
○ BP
○ Volume status Initial investigations
○ Us and Es , Bl glucose
○ Bicarbonate
○ Urinary potassium
♦ low urinary K + ( < 20 mEq/L ) → suggests GI loss , poor intake or a shift of EC K+ to IC
♦ ↑ urinary K+ ( > 40 mEq/L ) → suggests renal loss
○ Calcium
○ Magnesium → if cause not obvious and moderate to severe hypokalaemia ECG
ECG Ask for an ECG if < 3.0 mmol/L Flat or inverted T waves Prominent U waves Depressed ST segment Prolonged QT interval 1st or 2nd degree heart block
Changes usually appear 
when K + < 2.7 mmol/ L
 Arrhythmias -commonly seen due to hypokalaemia include
○ atrial tachycardia with or without block
○ AV dissociation
○ Ventricular tachycardia
○ Ventricular fibrillation
General approach –Level of severity-
 speed of onset-What is the trend ? is there a rapid decline ?
compare to previous levels-What is the trend ? is there a rapid decline ?
compare to previous levels
Common causes –Most common cause seen in general practice is use of loop / thiazide diuretics
 Hypoaldosteronism – due to heart failure or liver disease is also common- 

consider Conns syndrome if ○ high serum sodium ○ normal or low potassium ○ refractory hypertension
 Increased losses eg from GI tract
Vomiting – if prolonged & patient is frail
 Movement of potassium into the intracelluluar fuid e.g alkalosis , burns or other trauma , medicines e.g high dose insulin
Groups at increased risk of arrhythmia –Some people are at ↑ ed risk of arrhythmia due to hypokalaemia – these include those who are taking Digoxin
the arrhytjmogenic potential of dogoxin is enhanced by hypokalaemia in patients with heart failure
 people with cardiac disease as
○ ischaemic heart disease
○ heart failure
○ left ventricular hypertrophy
 Co-existing hypomagnesemia -↓ Mg can induce renal K wasting. A combined deficiency may potentiate the risk of cardiac arrhythmias – both are pro-arrhythmic

management – based on level of potassium –
3.0 to 3.4 mmol/ L In most patients usually asymptomatic No ECG changes Consider oral replacement ( see hypokalaemia in adults- treatment ) Monitor and adjust treatment accordingly Correct any other co-existing electrolyte abnormality for e.g magnesium
2.5 to 2.9 mmol / L None or minor symptoms Refer for IV replacement if patient cannot tolerate oral preparations Decide on an individual basis based on circumstances Ensure more close monitoring if replacing with oral potassium in the community
Less than 2.5 mmol / L Intravenous replacement is indicated Immediate goal is to prevent or correct cardiac electrical disturbances and serious neuromuscular weakness Monitoring under hospital environment Arrange admission/ transfer
Discussion –Hypokalaemia is the most frequently seen electrolyte abnormality founs in hospitalised patients – occurring in up to 20 % of patients and is associated with an increased mortality in this group
 Consider additional tests if cause is unclear ( in 1ary care )
○ urinary potassium excretion ( not usually ordered in 1° care )
○ serum magnesium
○ serum bicarbonate ( if an acid-base disorder suspected )
○ check serum digoxin level is patient is on digitalis

Two common components of diagnostic evaluation are

 Trudge carefully in complicated scenarios for e.g
○ hypokalaemia in patient with heart failure who is taking digoxin in combination with a loop diuretic and an ACE inhibitor – decision of whether to administer potassium replacement can be complex
○ CKD patients
 Further evaluation of patients with persistent hypokalaemia can be complex and involve checking serum aldosterone , renin and imaging tests as CT. MRI of adrenal glands- Refer these patients to secondary care


PILs on this topic are a bit hard to find- few useful ones are listed below
PDF from Cheshire and Wirral Partnership NHS Foundation Trust

Cleveland Clinic has a useful page for patients

Advice on Potassium-rich food from Michigan Medicine UOM
This is a discharge instruction for patients with hypokalaemia who are being sent home from Fairview -list of food with high potassium contents
U Wave – an excellent article from Life in the Fast Lane
ECG changes in hypokalemia from the Permanente Journal
1-minute video on hypokalaemia
Another 5-minute video from EKG guy
Article available via Researchgate Kardalas, Efstratios & Paschou, Stavroula & Anagnostis, Panagiotis & Muscogiuri, Giovanna & Siasos, Gerasimos & Vryonidou – Bompota, Andromachi. (2018). Hypokalemia: A clinical update. Endocrine Connections. 7. EC-18. 10.1530/EC-18-0109.
Potassium physiology – hungry for knowledge ? master the topic
A 59 page PPt presentation by Dr Wingo
American Journal of Kidney Disease- Core curriculum Physiology and Pathophysiology of
Potassium Homeostasis: Core Curriculum

  1. Harrison’s manual of medicine -Dennis L. Kasper , Tinsley R Harrison McGraw-Hill
  2. Professional Making sense of the ECG -Andrew R.Houghton , David . Gray
  3. The ECG in practice- John R. Hampton ; With Contributions by David Adlam
  4. Hypokalaemia E Medicine accessed via
  5. Acid-base, fluids , and electrolytes- Robert F Reilly , Jr.,Mark A Perazella
  6. Medicine compendium Sando-K accessed via
  7. Investigating hypokalaemia BMJ 2013 ;347:f5137
  8. ABC of intravenous fluids , elctrolytes disorders and AKI management in adults via
  9. Serum potassium imbalance BPAC org via 
  10. Kardalas E, Paschou SA, Anagnostis P, Muscogiuri G, Siasos G, Vryonidou A. Hypokalemia: a clinical update. Endocr Connect. 2018;7(4):R135–R146. doi:10.1530/EC-18-0109 via
  11. Management of hypokalaemia Dr Anthony Crosse GMJ journal via
  12. Castro D, Sharma S. Hypokalemia. [Updated 2019 Feb 17]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan-. Available from:
  13. Lecturio hypokalemia



Related Charts:

Add Your Comments

Your email address will not be published.

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.

A4 Medicine  - Search Less and Learn More

Welcome to the A4 medicine community where we are constantly working to provide exceptional educational material to primary health care professionals. Subscribe to our website for complete access to our A4 Charts. They are aesthetically designed charts that contain 300 (plus and adding) common and complex medical conditions with the all information required for primary care in one single page that can help you in consultation/practice and exam.

Additionally, you will get complete access for our Learn From Experts : A4 Webinar Series in which domain experts share the video explainer presentation on one medical condition in one hour for the primary care. And you will also get a hefty discount on our publications and upcoming digital products.

We are giving a lifetime flat 30% discount to our first thousand users, discount code already applied to checkout.