Excessive thirst is an abnormal feeling of always needing to drink fluids.

Drinking lots of water is usually healthy. However, the urge to drink too much may be the result of a physical or emotional disease. Excessive thirst may be a symptom of high blood sugar (hyperglycemia). It can be an important clue in detecting diabetes.

Excessive thirst is a fairly common symptom. It is often the reaction to fluid loss during exercise, or to eating salty foods.

• A recent salty or spicy meal
• Bleeding enough to cause a significant decrease in blood volume
• Diabetes
• Diabetes insipidus
• Drugs such as anticholinergics, demeclocycline, diuretics, phenothiazines
• Excessive loss of water and salt (possibly due to not drinking enough water, profuse sweating, diarrhea, or vomiting)
• Loss of body fluids from the bloodstream into the tissues due to:
  • Conditions such as severe infections (sepsis) or burns
  • Heart, liver, or kidney failure
• Psychogenic polydipsia, the result of a mental disorder

Because thirst is usually the body's signal to replace water loss, it is usually appropriate to drink plenty of liquids.

A very strong, constant urge to drink may be a sign of a psychological problem, which may mean psychological help is needed.

For thirst caused by diabetes, follow the prescribed treatment to properly control blood sugar levels.

• Excessive thirst is persistent and unexplained
• Thirst is accompanied by other unexplained symptoms, such as blurry vision and fatigue
• You are passing more than 5 quarts of urine per day

The health care provider will get your medical history and perform a physical examination.

Medical history questions may include the following:

• How long have you been aware of having increased thirst?
• Is it consistent during the day?
• Is it worse during the day?
• Did it develop suddenly or slowly?
• Are you eating more salty or spicy foods?
• How much salt do you have each day?
• Did you change your diet?
• Have you noticed an increased appetite?
• Have you noticed an unintentional weight gain?
• Have you noticed an unintentional weight loss?
• Has your activity level recently increased?
• What other symptoms are happening at the same time?
• Have you recently suffered a burn or other injury?
• Are you urinating more or less frequently than usual?
• Are you producing more or less urine than usual?
• Have you noticed any bleeding?
• Are you sweating more than usual?
• Is there any swelling in your body?
• Do you have a fever?

A psychological evaluation may be recommended if the health care provider suspects a psychological compulsive thirst. Your fluid intake and output will be closely watched.

Diagnostic tests that may be performed include the following:

• Blood glucose level
• CBC and blood differential
• Serum calcium
• Serum osmolality
• Serum sodium
• Urinalysis
• Urine osmolality

Robinson AG, Verbalis JG. Posterior pituitary. In: Kronenberg HM, Shlomo M, Polonsky KS, Larsen PR, eds. Williams Textbook of Endocrinology. 11th ed. Philadelphia, Pa:Saunders Elsevier; 2008:chap 9.

Oh MS. Evaluation of renal function, water, electrolytes, and acid-base balance. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 21st ed. Philadelphia, Pa: Saunders Elsevier;2006:chap 14.