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A cat that suddenly drinks a lot of water (polydipsia) almost always has an underlying medical cause. There are 5 common serious. Free WhatsApp consultation.

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Cat Drinking Excessively: Diabetes, Kidney, or Thyroid?

20 April 2026
3 min read
Cat Drinking Excessively: Diabetes, Kidney, or Thyroid?

If your cat suddenly keeps going back and forth to the water bowl, or the water disappears much faster than usual — that's not something to ignore. Polydipsia (excessive drinking) in cats almost always points to a medical condition that needs attention.

The good news: nearly all causes can be managed well if caught early.

How to Measure If Your Cat Is Really Drinking Too Much

Don't Wait Until It's Too Late!

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Before going to the vet, measure first:

  1. Fill the water bowl with a known amount in the morning (e.g., 500 ml)
  2. Make sure no other water source is accessible (toilet, leaky faucet)
  3. Note how much is left the next morning
  4. Calculate: water consumed = initial amount − leftover
  5. Normal: ~50 ml/kg/day. Example for a 4 kg cat: normal = 200 ml. Above 400 ml = needs to be checked.

5 Main Causes of Excessive Drinking in Cats

1

Chronic Kidney Disease (CKD)

The most common cause of polydipsia in older cats. Damaged kidneys can't concentrate urine → dilute urine in large volumes → cat must drink more to compensate. More than half of cats over 12 years old have some level of CKD.

Other signs: Weight loss, decreased appetite, vomiting, urine-smelling breath, lethargy
Diagnosis: Bloodwork (BUN, creatinine, SDMA) + urinalysis. Stages 1–4 each have different approaches.
2

Diabetes Mellitus

High blood glucose pulls water into the urine via osmosis → sweet, dilute urine → the cat is constantly thirsty. More common in overweight, male, and neutered cats. Often comes with increased appetite but weight loss.

Hallmark signs: Eats a lot but loses weight, walks with hocks touching the floor (plantigrade stance)
Diagnosis: High blood glucose + glucose in urine. High remission chance if treated early.
3

Hyperthyroidism

An overactive thyroid raises metabolism, blood pressure, and renal blood flow → more urine → more thirst. Very common in cats over 10 years old. Often co-occurs with CKD, complicating diagnosis.

Hallmark signs: Very active/restless beyond their age, eats a lot but stays thin, racing heart, occasional vomiting
Diagnosis: Blood T4 level. Very responsive to methimazole treatment.
4

Pyometra (Uterine Infection)

Bacteria in a uterine infection produce toxins that interfere with the kidneys' ability to concentrate urine → polydipsia. Usually accompanied by other more obvious symptoms. More common in dogs but can occur in unspayed female cats.

Other signs: Enlarged abdomen, discharge from vulva (open pyometra), lethargy, fever
Emergency: Requires surgery promptly. Can be fatal if untreated.
5

Diabetes Insipidus & Other Conditions

Less common: diabetes insipidus (lack of ADH or kidneys unresponsive to it), hypercalcemia, hypokalemia, liver disease, or side effects of certain medications (corticosteroids). Comprehensive bloodwork can rule these out.

Tests Typically Performed

  • Complete blood count (CBC) — checks for infection, anemia, blood cells
  • Chemistry panel — BUN, creatinine (kidneys), ALT/AST (liver), glucose, calcium
  • T4 — thyroid hormone level (for hyperthyroidism)
  • SDMA — kidney marker more sensitive than creatinine
  • Urinalysis + urine specific gravity — the kidneys' ability to concentrate urine
  • Abdominal ultrasound — condition of the kidneys, uterus, liver

Cat Drinking Excessively? Get It Checked Now

All of the conditions above are easier to manage when caught early. Birawa Vet doctors can come to your home for an exam and blood collection — results are usually back within hours.

Book a Home Exam

Frequently Asked Questions

How much water is normal for a cat to drink per day?
Cats eating dry food: about 200–250 ml per day (roughly 1 glass). Cats eating wet food: less, since the food contains 70–80% water. Polydipsia is defined as drinking more than 100 ml per kg of body weight per day — so a 4 kg cat drinking more than 400 ml/day warrants concern. Easy method: fill the water bowl with a measured amount in the morning and check the remainder that evening.
Does a cat drinking a lot of water definitely mean diabetes?
Not necessarily — excessive drinking (polydipsia) is a symptom of many conditions, not just diabetes. Chronic kidney disease (CKD) is actually more common in older cats. Hyperthyroidism, diabetes insipidus, and liver disease can also cause this symptom. Only blood and urine tests can distinguish between them.
Can diabetes in cats be cured?
Yes — about 25–50% of diabetic cats can achieve remission (no longer needing insulin) if treated aggressively early: the right insulin dose, a very high-protein and low-carbohydrate diet, and maintaining an ideal body weight. The sooner it is diagnosed and treated, the greater the chance of remission.
Why do cats with kidney disease drink a lot of water?
Damaged kidneys lose the ability to concentrate urine. As a result, the cat produces large volumes of dilute urine (polyuria) and must drink more to compensate for that fluid loss. This is the classic polydipsia-polyuria (PU/PD) mechanism in CKD.
What should you do if you suspect your cat is drinking excessively?
First step: measure water intake over 24 hours using a measured container. If intake is indeed high, see a veterinarian promptly. The vet will perform a complete blood count (CBC + chemistry panel including BUN, creatinine, glucose) and urinalysis to determine the cause. Don't wait for the condition to worsen — kidney disease and diabetes are much easier to manage when caught early.
BV

Medically Reviewed by

Birawa Vet Medical Team

This article has been verified by our medical team to ensure veterinary information accuracy.

Medical Disclaimer

The information in this article is for general educational purposes only and is not a substitute for direct consultation with a veterinarian.

Every pet has unique conditions. Do not hesitate to seek professional help if your pet is sick.

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