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 by the kidneys, and can on rare occasions be life-threatening as the body's serum sodium level is diluted to an extent that seizures and cardiac arrest can occur. While psychogenic polydipsia is generally not found outside the population of serious mental disorders, there is some anecdotal evidence of a milder form (typically called 'habit polydipsia' or 'habit drinking') that can be found in the absence of psychosis or other mental conditions. The excessive levels of fluid intake may result in a false diagnosis of diabetes insipidus, since the chronic ingestion of excessive water can produce diagnostic results that closely mimic