Water Deprivation Test (Investigation Guide)
A water deprivation test assesses how your body regulates fluid balance, and is used to investigate excessive thirst and urination, including diabetes insipidus (distinct from diabetes mellitus).
Why it's done
- distinguish diabetes insipidus from other causes of excessive thirst and urination
- identify the underlying cause
- guide the right treatment
What we offer
- the test carried out under close medical supervision
- regular monitoring of weight, blood and urine throughout
- desmopressin given partway through where needed to clarify the diagnosis
What the test assesses
A supervised water-deprivation test helps investigate excessive thirst and urination by assessing the body’s ability to concentrate urine and its response to desmopressin. Results may help distinguish arginine vasopressin deficiency, renal resistance to vasopressin and primary polydipsia.
Safety and preparation
This test must be performed under specialist supervision because dehydration and abnormal sodium levels can be dangerous. Follow the testing unit’s instructions about fluids and medicines. Do not restrict fluids at home unless specifically instructed by the responsible clinical team.
Results and UK-wide review
Interpretation uses weight, symptoms, urine concentration, blood concentration and sodium measurements over time. Results can usually be reviewed securely by video, but the test itself requires an appropriate monitored facility.