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).  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.
Professor of Medicine
University of Iowa
Des Moines Internal Medicine Residency Training Program
Veterans Affairs Medical Center
UK is an author of references cited in this topic.
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.
Department of Internal Medicine
Division of Nephrology
University of Iowa Hospital and Clinics
MS declares that he has no competing interests.
Associate Professor of Clinical Medicine
Chicago Medical School
Rosalind Franklin University of Medicine and Science
Associate Program Director
Department of Medicine
Mount Sinai Hospital
SCH declares that he has no competing interests.
DK declares that he has no competing interests.
Use of this content is subject to our disclaimer