Polydipsia is a medical symptom in which the patient drinks abnormally large amounts of fluids. The word derives from the Greek πολυδιψία, the feminine of πολυδίψιος (polydipsios), "very thirsty and that from πολύς (polys), "much, many" + δίψα (dipsa), "thirst". The fluid is usually water, though some people may think of alcohol because of the etymologically related term dipsomaniac, meaning an alcoholic.
It is often, and characteristically, found in diabetics, often as one of the initial symptoms, and in those who fail to take their anti-diabetic medications or whose dosages have become inadequate. It is also caused by other conditions featuring osmotic diuresis and by diabetes insipidus ("water diabetes"), and forms part of the differential diagnostic tree for them, as well. Polydipsia is also a symptom of atropine or belladonna poisoning. Another cause can be due to medication (such as diuretics) or inadvertent consumption of caffeine. One who drinks nothing but coffee or soda can be easily misdiagnosed by a medical professional as psychogenic polydipsia, as they may be unaware they are consuming diuretics.
For the main article, see Psychogenic polydipsia.
Psychogenic polydipsia is a type of polydipsia seen in some patients with mental illnesses such as schizophrenia, and/or the developmentally disabled. It should be taken very seriously, as it can be life threatening as serum sodium is diluted to an extent that seizures and cardiac arrest can occur. Institutionalization may be necessary, as the condition can be difficult to manage. Patients have been known to seek fluids from any source possible.
While psychogenic polydipsia is generally not found outside the population of those with serious mental disorders, there is some anecdotal evidence of a milder form (typically called 'habit polydipsia' or 'habit drinking') that can occasionally 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 those of mild diabetes insipidus.
Polydipsia is a symptom, not a disease (cause). To diagnose the cause of polydipsia a fluid deprivation test is used, which may require a patient to abstain from water, and for blood and urine tests to be undertaken. Additional blood work may be required to test for the presence of diuretics, such as caffeine, or recreational drugs. Finally neurological testing may be required to determine if there has been damage to the hypothalamus. These tests are routinely used in diagnosing diabetes insipidus.