Published: August 8, 2013
Last reviewed: December 31, 2022

What Is Polydipsia: Definition

Polydipsia means excessive thirst [from Greek poly = much; dipsia = thirst], which is defined as drinking at least 100 mL of water per kilogram of body weight per day, which would be 7 liters per day for a 70 kg person 28. Excessive thirst developing within hours/days is usually due to dehydration. Stronger thirst continuing for a prolonged time may result from an underlying disease, such as diabetes mellitus.

Polydipsia can be either the cause or result of excessive urination (polyuria).

A related condition is beer potomania.

A. Causes of Excessive Thirst WITHOUT Excessive Urination

1. Dehydration due to:

  • Excessive sweating (diaphoresis)
  • Diarrhea
  • Large loose stools after eating foods high in fiber
  • Hyperventilation due to anxiousness, certain diseases, such as pneumonia, or at high altitudes.
  • References: 1,3

2. Dry mouth by causes other than dehydration:

Acute (sudden) causes of dry mouth:

  • Eating dry or spicy or salty foods
  • Breathing dry air, breathing through the mouth, snoring, smoking, chewing tobacco
  • Anxiety, depression, stress 45
  • Hangover
  • Disorder of salivary glands (mumps, side effect of irradiation) 42
  • Stroke 42
  • Shock (hypovolemic, septic, anaphylactic)

Chronic causes of dry mouth (xerostomia):

  • Anemia
  • Hypertension
  • Oral thrush caused by fungal [candida] infection
  • Disorders of salivary glands (sialadenitis, stones)
  • Autoimmune diseases: Sjögren’s syndrome, systemic lupus erythematosus (SLE), systemic sclerosis, sarcoidosis (neurosarcoidosis), rheumatoid arthritis
  • Parkinson’s disease
  • Alzheimer’s disease
  • Mouth or throat cancer
  • Cystic fibrosis
  • References: 37,42

Dry mouth as a side effect of medications or supplements:

  • Anti-acne drugs: isotretinoin, tretinoin 42
  • Anticholinergics (spasmolytics): atropine 47
  • Antidepressants: fluoxetine
  • Antidiarrheals: bismuth subsalicylate, loperamide 42
  • Antiemetics (drugs to treat nausea/vomiting): chlorpromazine, metoclopramide, ondansetron, promethazine, scopolamine 42
  • Antihistamines 42
  • Antiepileptics: valproate, topiramate 42
  • Antiparkinsonians 42
  • Antipsoriatics: acitretin 19
  • Antipsychotics: modafinil, phenothiazines, risperidone, indapamide
  • Antivirals: ritonavir, indinavir; antiretrovirals (to treat AIDS) 5
  • Aspirin overdose 15
  • Beta-blockers (for heart disease, hypertension): atenolol, propranolol 37
  • Bronchodilators (to treat asthma): theophylline, salbutamol 42
  • Chemotherapeutics: bortezomib, cisplatin 22
  • Muscle relaxants 42
  • Nasal decongestants (sprays) 42
  • Non-steroidal anti-inflammatory drugs (NSAIDs): aspirin, diclofenac,  ibuprofen, naproxen 51
  • Opiates: morphine 43
  • Sedatives (sleeping pills: diazepam) 42
  • Steroids
  • Stimulants: armodafinil 50

Illegal Drugs:

  • Marijuana (cannabis) 48
  • Ecstasy (MDMA) 42
  • Cocaine 48
  • Heroin 48
  • Amphetamine 48

B. Causes of Excessive Thirst AND Excessive Urination

Psychogenic Polydipsia

In most cases of polydipsia, people drink water to replace the water they have lost due to excessive urination caused by certain organic disorders. Individuals with primary or psychogenic polydipsia (often associated with schizophrenia) have no organic disorder, but they believe or feel they should drink a lot of fluid. This can lead to water intoxication (hyponatremia), which can be life-threatening.

Brain Disorders Resulting in Central Diabetes Insipidus

  • Head injury, tumor, stroke 7,8

Impaired Kidney Function Resulting in Nephrogenic Diabetes Insipidus

  • Salt-wasting nephropathy (in a polycystic kidney disease), post-obstructive diuresis (after resolution of urinary tract blockage) 20, medullary kidney cystic disease 1, proximal renal tubular acidosis 1

Heart Disorders

  • Supraventricular tachycardia (a type of heart arrhythmia) 29, postural hypotension, systemic capillary leak syndrome 1

Hormonal Disorders

  • Gestational diabetes insipidus; in the 3rd trimester of pregnancy 44
  • Adrenal hyperactivity 10,11,35
  • Epinephrine (adrenaline)-secreting tumor (pheochromocytoma) in the adrenal medulla 13
  • Pituitary disorders:
    • Cushing’s syndrome 34
    • Sheehan’s syndrome (pituitary infarct)
  • Hyperthyroidism, especially acute severe thyrotoxicosis (thyroid storm) (hyperglycemia, excessive sweating and diarrhea lead to polydipsia)
  • Hyperparathyroidism 17

Metabolic Disorders

  • Hypokalemia 20,23
  • Hypercalcemia 22
  • Hypernatremia 24

Genetic and Congenital Disorders

  • Aceruloplasminemia 1
  • Alsing syndrome 1
  • Bartter’s syndrome
  • Boichis syndrome 1
  • Cystinosis
  • DEND syndrome 1
  • EAST syndrome 1
  • Fanconi syndrome 21
  • Froelich’s syndrome 1
  • Gitelman syndrome
  • Liddle’s syndrome
  • Nephronophthisis 1
  • Schroeder syndrome
  • Wolfram (DIDMOAD) syndrome
  • Apparent Mineralocorticoid Excess Syndrome 1

Other Disorders

  • Adiposogenital dystrophy
  • Langerhans cell histiocytosis 1
  • Omega-3 FFA deficiency syndrome
  • Sarcoidosis (neurosarcoidosis) 18
  • Tumors/cancers:
    • Adrenal adenoma 10
    • Ganglioblastoma
    • Glucagonoma — glucagon secreting tumor (gluconeogenesis > hyperglycemia > polydipsia) 16
    • Multiple myeloma 22
    • Pheochromocytoma 13


  • Amphotericin B 22
  • Antiobesity drugs: lorcaserin, orlistat, phentermine, sibutramine 42,46
  • Caffeine intoxication (excessive coffee or tea drinking)
  • Demeclocycline 22,39
  • Diuretics
  • Lithium 22
  • Vitamin D overdose (hypervitaminosis D) 49


  • Acid ingestion
  • Amanita muscaria (fly agaric) and other toxic mushrooms
  • Arsine gas
  • Belladonna-like plant
  • Bloodroot
  • Death camas
  • Horse nettle intake
  • Jimsonweed/Jamestown weed ingestion
  • Meadow Saffron plant
  • Mercury poisoning in children (acrodynia, pink disease)
  • Yellow jessamine (jasmine poisoning)
  • Snake bites 33


  • X-ray, CT or MRI investigations that involve injecting a contrast substance into your vein may be followed by excessive urination and thirst lasting for up to 24 hours 58


Excessive thirst is usually associated with fluid loss due to:

There are at least four mechanisms by which fluid loss from the body results in thirst 36:

  1. Dehydration, which stimulates osmoreceptors in the hypothalamus
  2. Hypovolemia (low blood volume), which stimulates volume receptors in the right atrium
  3. Hypotension (low blood pressure), which stimulates baroreceptors in aortic and carotid arch
  4. Decreased kidney perfusion, which stimulates renin and this angiotensin 2 release, which stimulates the feeling of thirst in the brain.

Associated Symptoms

  • Individuals with polydipsia usually complain that they are “always thirsty,” “desperate to drink” and they “urinate a lot.”
  • Drinking large amounts of fluids, drinking at night (nocturnal polydipsia)
  • Excessive urination (polyuria; >3 liters urine per day), except in dehydration caused by sweating, hyperventilation, vomiting or diarrhea
  • Urination at night (nocturia), wetting clothes or bed in children (enuresis)
  • Symptoms due to dehydration: dry mouth, dry skin, dizziness, fainting, weakness, fatigue
  • Symptoms of an underlying disease, for example:
    • Weight loss in diabetes mellitus and insipidus
    • Quick, temporary weight gain (in primary polydipsia or anorexia nervosa — 1 liter of water is 1 kilogram or about 2 pounds)
    • Excessive hunger (polyphagia) or loss of appetite in diabetes


  • Signs of dehydration: dry mucous membranes, dry, wrinkled skin, decreased skin elasticity (prolonged skin turgor)
  • Signs of long-term untreated diabetes:
    • Eye problems: cataract, papilledema, retinal hemorrhage, visual field deficit
    • Peripheral neuropathy: numbness in hands and feet


A doctor can find a cause of polydipsia from symptoms, signs and laboratory tests.

TABLE: Common causes of excessive thirst with typical symptoms and lab values

CONDITION SYMPTOMS AND SIGNS (besides excessive urination and thirst) LAB TESTS
Dehydration Sudden weight loss, dark urine (decreased, not increased urination) Decreased 24-hour urine; in mild and moderate d.: normal blood sodium; in severe d.: increased blood sodium
Heat exhaustion or heat stroke Exhaustion, cool, clammy skin, increased body temperature (in heat stroke: warm skin, body T > 105.8 °F or 41 °C) Decreased 24-hour urine
Diabetes mellitus 31 Hunger or poor appetite, weight loss, extreme fatigue, blurred vision, jock itch, diabetes in family Increased glucose levels in the blood and urine
Diabetes insipidus (central and nephrogenic) 22,32 History of brain trauma, surgery or tumor, or a kidney disease Decreased urine specific gravity and osmolality, increased blood sodium
Diuretics Dry mouth Decreased urine specific gravity
Psychogenic polydipsia Usually in individuals with schizophrenia treated with antipsychotics Increased 24-hour urine, decreased urine specific gravity and osmolality, sometimes: decreased blood sodium
Adrenal hyperactivity (hyperaldosteronism) Increased blood pressure Decreased blood potassium, increased urine potassium, increased blood aldosterone after sodium challenge
Anorexia nervosa Severely decreased body weight Mineral and vitamin deficiencies (hypokalemia, low iron, etc.)
Postural (orthostatic) hypotension Dizziness after raising up, Drop of blood pressure > 30 mm Hg upon standing Nothing typical
Hypertension 35 Increased blood pressure Possible increase of blood aldosterone, renin
Anemia 38 Paleness, fatigue, hyperventilation Decreased RBC or abnormal erythrocytes
Congestive heart failure 36 Chest pain, swollen legs ECG abnormalities
Liver cirrhosis 12,40,41 History of alcoholism, poor appetite, loss of weight, spider nevuses Decreased serum proteins (albumin), increased liver enzymes and bilirubin
Chronic dry mouth (xerostomia) in Sjögren’s syndrome and SLE Rash, joint pain Specific antibodies in the blood
Shock (hypovolemic, septic, anaphylactic) Cool, clammy skin, increased heart rate; in late shock: lethargy, low blood pressure Septic shock: increased or decreased white blood cells (WBC), increased blood glucose
Ecstasy (MDMA) 35cocaine, marijuana 48 Euphoria Positive urine drug test
Opiates (morphine, heroin) Sleepiness Positive urine drug test
The following part is a bit more technical.

Laboratory Tests in Detail

Blood Tests

  • Glucose
    • Elevated:
      • Diabetes mellitus
      • Cushing’s syndrome
      • Early phase of hypovolemic shock (bleeding)
      • Pheochromocytoma 13
  • Sodium:
    • Normal levels (135-145 meq/L):
      • In most cases of dehydration (diarrhea, vomiting, excessive sweating)
      • Within 8 hours of onset of acute bleeding
    • Hyponatremia (<135 meq/L):
      • >8 hours after onset of bleeding, when interstitial fluid moves into the intravascular space
      • Sometimes after repeated vomiting or severe diarrhea
      • Water intoxication
      • Diabetic ketoacidosis (usually) 9
      • Cerebral salt wasting (head injury, tumor) 26
    • Hypernatremia (>145 meq/L):
      • Dehydration (sometimes) 22
      • Diabetes insipidus 22
  • Potassium:
    • Hypokalemia:
      • Hyperaldosteronism
      • Anorexia nervosa
      • Hyperthyroidism
    • Hyperkalemia:
      • Diabetic ketoacidosis (usually) 9
  • Calcium:
    • Hypercalcemia:
      • Hyperparathyroidism
      • Hypervitaminosis D
    • Hypocalcemia:
      • Diabetic ketoacidosis (usually) 9
  • CBC:
    • White blood cells increased or decreased in sepsis
  • Hematocrit (HCT):
    • Decreased in water intoxication
  • Blood Urea Nitrogen (BUN):
    • Increased in kidney failure
    • Decreased in water intoxication
  • pH
    • <7.3 (diabetic ketoacidosis) 9
  • Proteins:
    • Hypoalbuminemia in liver cirrhosis, nephrotic syndrome, severe malnutrition
  • Hormone levels:
    • ADH
      • Decreased in central diabetes insipidus
      • Increased in nephrogenic diabetes insipidus
    • ACTH may be increased in pituitary adenoma or adrenal hyperplasia
    • Cortisol may be increased in adrenal adenoma
    • Aldosterone may be increased in adrenal adenoma or primary hyperaldosteronism

Urine Tests

  • Osmolality
    • <200 mOsm/kg in psychogenic polydipsia, diabetes insipidus 27
  • Specific gravity
    • <1.005 in diabetes insipidus
  • Glucose
    • Untreated diabetes mellitus 1 or 2 9
    • Pheochromocytoma; rare 13
  • Proteins
    • In nephrotic syndrome
  • Sodium
    • >20 meq/L: cerebral salt wasting 26


Treatment depends on the cause.

Complications: Water Intoxication

Excessive drinking in combination with low food and hence salt intake (chronic alcoholism, anorexia nervosa, psychogenic polydipsia) may lead to water intoxication with hyponatremia and brain edema. Symptoms may include nausea, vomiting, headache, lethargy, confusion, seizures, coma and eventual death.

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