Increased or Excessive Thirst (Polydipsia) in Cats

Key Takeaways

Polydipsia in cats is a noticeable increase in thirst. Cats who drink in excess of 100 milliliters of water for every kilogram of body weight (approx 1.5oz per lb) are considered polydipsic. 

• Often the first sign is that the water bowl needs to be filled more often than usual

• The first step to diagnosing polydipsia is careful measurement and recording of the amount of water the cat is drinking

Cats consuming large amounts of water require prompt veterinary attention

• Causes of polydipsia include chronic kidney disease, hyperthyroidism, and diabetes mellitus

• Diagnostic tools include physical examination, blood tests, and urinalysis

• Treatment and outcomes are difficult to generalize due to the variety of underlying causes

A Closer Look: What is Polydipsia in Cats?

Polydipsia is caused by disruptions to any of the systems involved in thirst and urine production. These include:

• Thirst center (the part of the brain that controls thirst)

• Kidneys

• Endocrine system, including the hypothalamus and pituitary glands

• Circulatory system

• Respiratory system

Cats’ consumption of water varies day to day. In cases where medically relevant increased thirst is suspected, measuring consumption is advised. Drinking in excess of 100 ml/kg (~1.5oz/lb) is the characteristic sign of polydipsia. 

Note: Limiting the amount of water consumed by the cat is not advised. Polydipsia is typically a compensatory behavior that helps the cat cope with an underlying illness. Limiting access to water can worsen conditions, making the cat sicker. In extreme cases, limiting access to water is fatal.

Possible Causes

The conditions most likely to be associated with polydipsia in cats include:

Chronic kidney disease

Hyperthyroidism 

Diabetes mellitus

In rarer cases, polydipsia is associated with:

• Liver disease

Diabetes insipidus

• Pyometra (the accumulation of pus in the uterus)

Toxicosis

• Side effect of certain medications

Risk Factors

Polydipsia is common in cats. The amount of water a cat drinks varies from day to day, depending on activity level, the weather, and a number of other factors. In cases where the typical volume is noticeably exceeded for several days in a row, prompt veterinary attention is required. If other symptoms occur at the same time, including fever, changes in behavior, or refusal to eat, immediate care is required. 

Polydipsia is most common in older cats or obese cats, but any cat consistently drinking noticeably more than usual requires veterinary attention.

Testing and Diagnosis

In cases where the cat is drinking noticeably more than usual, the first step is to determine how much water is being consumed. Measuring the quantity of water that goes into the water bowl, and keeping a record of daily consumption is advised. Noting other reasons the water may be disappearing (other pets or spillage, for example) is also useful.

If the amount being consumed is more than 100 milliliters per kilogram of body weight over a number of days, veterinary care is required to diagnose underlying conditions. 

Diagnostic tools include:

• Physical examination

• Blood test

• Urinalysis

• Diagnostic imaging, such as X-ray or ultrasound

• Specific testing for hormone-related diseases

In some cases, diagnosis of the underlying cause may require multiple tests, or therapeutic trials where the response to a medication is used to rule out certain conditions.  Treatment depends on underlying conditions and may include:

• Dietary management

• Surgery

• Medications, such as steroids, antibiotics, or diuretics 

• Reducing or discontinuing use of drugs that are causing side effects

Similar symptoms

It is possible to mistake polydipsia for normal water consumption, especially if the cat is more active than usual or if the weather is hot.

Associated Symptoms

Often, a cat with polydipsia also has polyuria (excessive urination). Other associated symptoms depend on underlying causes. These include:

Weight loss

Weight gain

• Reduced appetite

Bad breath

Vomiting

Lethargy

• Weakness

• Difficulty urinating

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