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
Medical sign or reported by the patient: In some senses, the process of diagnosis is always a matter of assessing the "likelihood" that a given condition is present in the patient. In a patient who presents with haemoptysis (coughing up blood), the haemoptysis is very much more likely to be caused by respiratory disease than by the patient having broken their toe. Each question in the history taking allows the medical practitioner to narrow down their view of the cause of the symptom, testing and building up their hypotheses as they go along. Examination, which is essentially looking for clinical signs, allows