Fluid deprivation test Fluid deprivation test A fluid or water deprivation test is a medical test which can be used to determine whether the patient has diabetes insipidus as opposed to other causes of polydipsia (a condition of excessive thirst that causes an excessive intake of water). The patient is required, for a prolonged period, to forgo intake of water completely, to determine the cause of the thirst. This test measures changes in body weight, urine output, and urine composition when fluids are withheld. Sometimes measuring blood levels of ADH (a synonym for vasopressin) during this test is also necessary. If there is
Polydipsia those of mild diabetes insipidus. As discussed in the entry on diabetes insipidus, "Habit drinking (in its severest form termed psychogenic polydipsia) is the most common imitator of diabetes insipidus at all ages. While many adult cases in the medical literature are associated with mental disorders, most patients with habit polydipsia have no other detectable disease. The distinction is made during the water deprivation test, as some degree of urinary concentration above isosmolar is usually obtained before the patient becomes dehydrated." However, prior to a water deprivation test, consideration should be given to a psychiatric consult to see whether it