classification of hyponatraemia

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Hyponatraemia can be classified according to the serum sodium concentration:

  • mild - sodium concentration is 125-135 mmol/l

  • moderate - sodium concentration is 115-124 mmol/l

  • severe - sodium concentration is <115 mmol/l

Classification according to volume status:

  • hypovolaemic hyponatraemia
  • euvolaemic hyponatraemia
  • hypervolaemic hyponatraemia (2)

Hyponatraemia is also classified according to the rate of onset (although calculating the duration of hyponatraemia is often difficult):

  • acute hyponatraemia - symptoms develop in less than 48 hours
  • chronic hyponatraemia - symptoms present for more than 48 hours (2,3)


Last reviewed 04/2022