Assessment of hypokalaemia

Last reviewed: March 2019

Last updated: June 2018

Summary

Hypokalaemia is defined as a serum potassium level <3.5 mmol/L (<3.5 mEq/L). Moderate hypokalaemia is defined as serum potassium levels of 2.5 to 3 mmol/L (2.5 to 3 mEq/L) and severe hypokalaemia defined as a serum potassium level <2.5 mmol/L (<2.5 mEq/L). [1] The ratio of intracellular to extracellular potassium determines, in part, the cellular membrane potential. Therefore small changes in the extracellular potassium level can have large effects on the function of the cardiovascular and neuromuscular systems.

Hypokalaemia is most commonly due to urinary or GI losses. A fall in serum potassium from 4 to 3 mmol/L (4 to 3 mEq/L) represents an approximate loss of 200 to 400 mmol (200 to 400 mEq) of potassium. However, these estimates do not always apply to patients with transcellular potassium redistribution. Clinical manifestations of hypokalaemia are typically seen only if the serum potassium is <3.0 mmol/L (<3.0 mEq/L).

Common acute manifestations are muscle weakness and ECG changes. More prolonged and profound hypokalaemia may cause rhabdomyolysis, renal abnormalities, and cardiac arrhythmias.

The rapidity and method of potassium repletion depends on:

The severity of hypokalaemia
The presence of associated conditions
The presence or absence of signs and symptoms
The expectation of continued losses.

Obtaining an ECG is recommended for all patients with hypokalaemia. Frequent monitoring of the serum potassium concentration is also recommended to ensure appropriate repletion and to avoid hyperkalaemia.

Differentials

Common

Vomiting
Severe diarrhoea
Laxative and bowel cleansing agent use
Bulimia nervosa
Anorexia nervosa
Drug-induced
Alcoholism
Diabetic ketoacidosis
Non-ketotic hyperglycaemia
Renal tubular acidosis (RTA)
Exercising in a hot climate
Stress response in critical illness

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Uncommon

Villous adenoma
VIPoma
Ileal loop/conduit with ureteric implants
Dialysis or plasmapheresis
Primary aldosteronism
Apparent mineralocorticoid excess
Cushing's syndrome
Hypomagnesaemia
Hypokalaemic periodic paralysis
Central diabetes insipidus (DI)
Congenital adrenal hyperplasia due to 11-beta-hydroxylase deficiency
Bartter's syndrome
Gitelman's syndrome
Liddle's syndrome
Renal disease associated with Sjogren's syndrome
Renal disease associated with lupus nephropathy
Burns
Eczema involving a large surface area
Psoriasis involving a large surface area
Cystic fibrosis (CF)
Primary (often psychogenic) polydipsia
Hypothermia

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Contributors

Authors VIEW ALL 

Udaya Kabadi, MD

Professor of Medicine

University of Iowa

Des Moines Internal Medicine Residency Training Program

Staff Endocrinologist

Veterans Affairs Medical Center

Des Moines

Disclosures

UK is an author of references cited in this topic.

Acknowledgements

Dr Udaya Kabadi would like to gratefully acknowledge Dr Sumit Sharma and Dr Preeti Agrawal, previous contributors to this monograph. SS and PA declare that they have no competing interests.