21st May 2025

You are asked to review a 65-year-old lady with a sodium of 113 mmol/L as she has become acutely confused.

You are asked to review a 65-year-old lady with a sodium of 113 mmol/L as she has become acutely confused. She has a background of type 2 diabetes. On assessment her observations remain stable. Blood glucose levels are 9 mmol/L. Serum osmolality is 240 mOsmol/kg. Urine osmolality is 150 mOsmol/kg. Urine sodium is 20 mmol/L. She is euvolaemic on examination.

Which of the following causes would most likely account for the hyponatraemia? Please select only ONE answer.