Increased Thirst (Polydipsia) in Dogs

Summary

Increased thirst, or polydipsia, is a common symptom of many conditions in dogs. Pet parents may conclude a dog is excessively thirsty based on subjective observations, like suddenly finding the water bowl is constantly empty, or from objective measurements. Individual variations are expected, but daily water consumption in excess of 100 mL per kg of body weight is considered excessive. 

Thirst after exercise or exertion is normal. A dog that is persistently thirstier than usual may have serious underlying conditions such as kidney disease, pyometra, or diabetes mellitus. Conditions that cause excessive urination often lead to excessive drinking as a secondary symptom. Sudden excessive thirst might indicate poisoning. 

The typical diagnostic approach for a dog showing excessive thirst begins with a physical examination, blood work, and urinalysis.

Guidelines

Increased thirst is a common symptom of multiple conditions. Persistent or sudden increased thirst with no known cause such as exercise, or along with other symptoms of illness, is cause for concern and warrants medical attention.

Increased thirst indicates an EMERGENCY if observed with the following symptoms:

• Vomiting • Weakness and collapse • Inability to walk • Seizures

• Persistent pain, vocalizations, or distress

Increased thirst may indicate a serious underlying condition when associated with:

• Significant changes in appetite • Weight gain • Weight loss • Bloating • Lethargy

• Jaundice (yellow eyes, gums and skin) • Hair loss

Changes in thirst can indicate a worsening of an underlying condition. If a dog showing changes in thirst has been previously diagnosed with chronic conditions such as kidney failure, liver disease, or diabetes, seek urgent veterinary care. 

If a dog shows increased thirst but no other notable symptoms, it is best to seek non-emergency veterinary care to rule out serious conditions.

Possible Causes

Gradual but noticeable increase in thirst in dogs is commonly associated with the following general conditions:

• Kidney disease: anything that damages the kidneys, like an infection, toxin, or chronic degenerative change, can lead to excessive thirst.

• Liver disease: similar to kidney disease, a variety of conditions can alter liver function and excessive thirst may result. 

• Endocrine disease: hypothyroidism, diabetes mellitus, diabetes insipidus, and adrenal gland disease are examples of endocrine diseases that can result in excessive thirst. 

• Pyometra: an infection of the uterus.

• Psychogenic polydipsia: an exceedingly rare behavioral disorder in which the dog drinks excessively with no physiologic cause. This is diagnosed only when all other potential causes are ruled out. 

• Paraneoplastic syndrome: excessive thirst can be associated with some types of cancer. 

Sudden increased thirst may be one of the symptoms shown by dogs after ingesting a toxin  such as:

• Ethylene glycol (antifreeze) • Alcohol (ethanol, isopropanol) • Mushrooms (nephrotoxic)

• Chocolate • Grapes and raisins

Increased thirst is a side-effect of some medications including but not limited to:

• Corticosteroids (e.g. prednisone/prednisolone) • Diuretics • Seizure medication

Risk Factors

Increased thirst can be characterized as compensatory, occurring secondary to excessive urination (polyuria). 

A sudden onset of polydipsia combined with other symptoms is more likely to be an emergency.

Testing and Diagnosis

A dog with increased thirst usually requires the following diagnostics to determine the best course of action:

• Physical examination • Blood work • Urinalysis • Diagnostic imaging

• Water deprivation test: this test will only be suggested if other diagnostics are inconclusive, as it challenges the kidneys and bears a degree of risk to the impacted animal

• Therapeutic trial with desmopressin (used to treat diabetes insipidus)

Treatment varies depending on the underlying cause.

Similar symptoms

• Normal thirst • Nausea • Oral irritation, as occurs after eating or chewing on something that stings

Associated Symptoms

• Increased urination (polyuria) • Unexplained weight loss or weight gain

• Changes in appetite (increase or decrease)