Protocol of water deprivation/desmopressin test
| Preparation |
|---|
| Fluid given overnight before test |
| Avoid caffeine |
| Weigh patient |
| Liaise with laboratory before test begins |
| Dehydration phase |
| Draw blood and collect urine for osmolality measurements and urine volume measurement at 08:00 |
| Restrict fluids—an eight hour fast will usually suffice |
| Weigh patient at two hourly intervals |
| Collect blood and urine for osmolality and volume measurements at regular intervals—ideally every two hours |
| Stop test if weight loss exceeds 5% of starting weight or if thirst becomes intolerable |
| Supervise test closely to avoid patient drinking |
| Desmopressin phase: if diabetes insipidus has not been excluded |
| Inject intramuscular, subcutaneous or intravenous desmopressin 0.3 μg (this can be administered by fine insulin syringe if given subcutaneously) or 5 μg intranasally after the dehydration phase (at about 16:00) |
| Allow patient to eat and drink up to 1.5 times the urine volume passed during dehydration phase and beyond |
| Collect urine for osmolality and volume at about 20:00 |
| Draw blood and collect urine for osmolality and volume measurements at 09:00 next morning |