A 44-year-old woman with 3 months of polyuria, polydipsia, w…
A 44-year-old woman with 3 months of polyuria, polydipsia, weakness, dry skin, and frequent waking during the night to urinate. Her history is significant for bipolar disorder, and she is taking lithium carbonate. Vital signs are blood pressure 110/80 mmHg, heart rate 80 bpm, respiratory rate 16 breaths/min, and temperature of 98F (36.7C). Physical examination shows dry mucus membranes. Laboratory results are fasting glucose 90mg/dL, plasma osmolality 290 mOsmol/kg, and urine osmolality 300 mOsmol/kg. A water deprivation test results in serum osmolality of 310 mOsmol/kg and a urine osmolality of 300 mOsmol/kg. After the administration of desmopressin, urine osmolality remains at 300mOsmol/kg. What is the next best step in management?