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Reduced potassium

Last reviewed dd mmm yyyy. Last edited dd mmm yyyy

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Hypokalaemia is defined as serum potassium concentration below 3.5 mmol/l (1,2). It can be divided into:

  • mild - 3.1-3.5 mmol/L
  • moderate - 2.5-3.0 mmol/L
  • severe - <2.5 mmol/L

Hypokalaemia is the most common electrolyte abnormality in hospitalised patients.

  • When defined as a value of less than 3.5 mmol/L, hypokalaemia is found in 20% of hospital inpatients, but occurs in only 2% of otherwise healthy adults (1)
  • Approximately 5% of hospitalised patients with confirmed hypokalaemia have serum potassium concentrations of <3.0 mmol/l
    • up to 50% of patients with normal potassium on admission may develop hypokalaemia during their inpatient stay
  • an increased risk of hypokalaemia is seen especially in
    • psychiatric patients - due to the medication rather than their underlying illness
    • patients on peritoneal dialysis - due to a combination of K+ loss into peritoneal fluid, infection and poor nutrition (2)

Women are thought to be more susceptible to hypokalaemia than men, especially when given thiazide diuretics. This is probably due to reduced muscle mass and a smaller pool of exchangeable K+ (2)

Pseudohypokalaemia related to seasonal (summer) changes in ambient temperature has been described in some literature. It is caused by metabolic increases in Na+,K+­- ATPase (‘sodium pump’) activity and cellular uptake of K+ (2).

Note that hypokalaemia exacerbates digoxin toxicity.


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