Last reviewed 07/2022

This is one of the most common causes of hyponatraemia; patients produce an inappropriately concentrated urine when there is no discernible stimulus for release of antidiuretic hormone (1).

The following criteria should be fulfilled before a diagnosis of SIADH can be made:

  • persistent excretion of concentrated urine with no reason for ADH release
  • normal renal and adrenal function
  • no oedema or hypovolaemia should be present