{{SignSymptom infobox |
  Name        = Polydipsia |
  ICD10       =  |
  ICD9        =  |
}}
'''Polydipsia''' is a medical symptom in which the patient drinks abnormally large amounts of Greek   ''πολυδιψία'', the feminine of ''πολυδίψιος'' (''polydipsios''), "very thirsty"<ref>[http://www.perseus.tufts.edu/cgi-bin/ptext?doc=Perseus%3Atext%3A1999.04.0057%3Aentry%3D%2384779 Polydipsios, Henry George Liddell, Robert Scott, ''A Greek-English Lexicon'', at Perseus]</ref> 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. 

Polydipsia is almost always associated with dehydration due to polyuria (excessive urination), if the condition is prolonged beyond a few hours in those with functioning kidneys.

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 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.

===Polydipsia in Psychiatric Subsets===

''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''' eli '''vesijuoppous''' on tila, jossa potilaalla on jatkuvasti merkittävissä määrin kasvanut jano sekä poikkeuksellisen voimakas juomisen tarve.<ref>http://www.wrongdiagnosis.com/sym/polydipsia.htm</ref> 

Polydipsia saattaa olla merkki tietyistä fyysisistä sairauksista, kuten diabeteksesta (''diabetes mellitus'') tai vesitystaudista (''diabetes insipidus'').<ref>http://www.diabetesinsipidus.org/polydipsia_polyuria.htm</ref> Psykogeeninen polydipsia on polydipsian toinen muoto. Siinä kyseessä on psyykkinen oire, eikä mitään polydipsian selittävää sairautta tai elimellistä vikaa ole todettavissa. Useasti psykogeenisesta polydipsiasta kärsivällä on taustallaan myös muita mielenterveydellisiä ongelmia ja sairauksia. Liiallinen vedenjuonti saattaa joillakin selittyä erilaisilla ahdistuneisuustiloilla. Polydipsia ilmenee myös tiettyjen lääkeaineiden mahdollisena sivuvaikutuksena. Arviolta 10–25 prosentista pitkäaikaisista skitsofreenikoista tulee myös polydiptikkoja.<ref>http://ajp.psychiatryonline.org/cgi/content/full/160/2/385-a</ref>

Polydipsia voi liittyä polyurian, epätavallisen runsaan virtsanerityksen aiheuttamaan dehydraatioon. Hyvin nopeasti nautittu suuri määrä vettä saattaa olla merkittävä haitta potilaan terveydelle. Yleisiä komplikaatioita ovat aivoödeema, sekavuus ja kouristelu.<ref>http://plaza.fi/ellit/joogamatto/terveys/voiko-vetta-juoda-liikaa</ref> Voi ilmetä myös hengitysongelmia tai myrkytyskuolema.<ref>http://health.yahoo.com/topic/mentalhealth/resources/article/healthwise/aa47805</ref>