Last edited 02/2018 and last reviewed 07/2021

Hyperkalaemia is an increase in the level of potassium in the blood. There is no agreed definition of hyperkalaemia, but serum concentrations greater than 5.5 mmol/l is usually quoted

  • it can be divided into
    • mild - 5.5–5.9 mmol/L
    • moderate - 6.0–6.4 mmol/L
    • severe - ≥6.5 mmol/L (1)
  • in addition to the absolute serum K + value, the rate of rise of serum K + is also important

Co-existing metabolic disturbances may ameliorate (e.g. hypernatraemia, hypercalcaemia, and alkalaemia) or exacerbate (e.g. hyponatraemia, hypocalcaemia or acidosis) the effects of hyperkalaemia (2).

Repetitive consecutive measures of serum potassium are needed to determine if hyperkalaemia is sustained or a transient event (2).

  • evaluation of serum potassium must take into consideration the effects of changes in serum pH
    • if serum pH decreases (acidaemia), serum potassium increases because potassium shifts from the cellular to the vascular space
    • if serum pH increases (alkalaemia), serum potassium decreases because potassium shifts intracellularly (3)

The condition is seen in 1-10% of hospitalised patients (1)

Hyperkalaemia may be fatal as a result of arrhythmias and cardiac arrest.