Quick answer
A cat drinking a lot of water, and peeing more as a result, often has an underlying illness. The most common causes are kidney disease, diabetes and an overactive thyroid, especially in cats over 10. Book a vet visit within a few days for blood and urine tests, and go the same day if your cat is also vomiting, not eating or very tired.
A cat drinking a lot of water is easy to miss, because many owners don’t watch the bowl closely. If you’re not sure how quickly to act, our symptom check will tell you whether to go now, call today or book a visit this week.
How much water is too much for a cat?
Vets call increased thirst polydipsia. It nearly always comes with increased urination, called polyuria. Most of the time, the peeing comes first: the body loses too much water in the urine, and the cat drinks to replace it.
How much a cat drinks depends mostly on diet. Wet food is about 70 to 80 percent water, so cats on wet food may barely touch their bowl. Cats on dry food drink more.
International Cat Care uses a simple threshold. A cat drinking more than 100 ml of water per kilogram of body weight in a day is drinking more than usual. For a typical 4 kg (9 lb) cat, that’s more than about 400 ml, or roughly 1.7 cups, a day.
To measure it at home:
- Fill a measuring jug and pour a set amount into your cat’s bowls.
- After 24 hours, measure what’s left and subtract it.
- Put a bowl of water somewhere your cat can’t reach and measure how much evaporates. Take that off your total.
- Repeat for a few days, and write down the results for your vet.
In a multi-cat home, this is harder. Signs like fuller water bowls emptying faster, bigger or more frequent clumps in the litter box, or your cat drinking from taps and glasses are also useful clues.
What causes increased thirst in cats?
According to International Cat Care, the most common causes of increased thirst in cats are kidney disease, diabetes mellitus, hyperthyroidism and high blood calcium. Most of these are more common in older cats.
| Cause | Other common signs | Urgency |
|---|---|---|
| Diet change to dry food, or hot weather | Otherwise well, urine normal | Monitor |
| Chronic kidney disease | Older cat, weight loss, poor appetite, vomiting, poor coat | See vet soon |
| Diabetes | Big appetite, weight loss, large urine clumps, sometimes weak back legs | See vet soon |
| Hyperthyroidism | Older cat, hungry but losing weight, restless, vomiting | See vet soon |
| High blood calcium or liver disease | Varies, often poor appetite and weight loss | See vet soon |
| Diabetic ketoacidosis | Known or undiagnosed diabetic, vomiting, not eating, very weak | Emergency |
| Pyometra (womb infection) | Unspayed female, lethargy, sometimes vulvar discharge | Emergency |
| Poisoning (antifreeze, lilies) | Vomiting, wobbliness, not eating | Emergency |
Cats may also drink more for a short time after losing fluid through vomiting or diarrhea. Some medicines, such as steroids, can increase thirst too. Tell your vet about anything your cat is taking.
Our guides explain the three most common causes in detail: cat kidney disease, diabetes in cats and hyperthyroidism in cats.
Why is my senior cat drinking more and peeing more?
In a senior cat, drinking and peeing more is one of the most common early signs of illness. Aging itself doesn’t cause it. Chronic kidney disease, hyperthyroidism and diabetes are all much more common after about age 10, and increased thirst often shows up months before other signs.
In one study, cats diagnosed with chronic kidney disease were more likely to have shown increased thirst and urination in the year before diagnosis. Catching it early matters, because diet changes and treatment can slow kidney disease and keep cats well for longer.
Signs of peeing more include:
- Bigger or more clumps in the litter box
- Needing to scoop or change litter more often
- Urinating outside the litter box, because the box fills faster or your cat can’t hold it
- Wet or clumpy litter stuck to paws
A senior cat that’s drinking more should have a checkup within a week or two, even if they seem well otherwise. Most vets also recommend checkups every 6 months for cats over 10.
How will my vet find out why my cat is drinking so much?
Your vet will usually start with a physical exam, a weight check and questions about appetite, diet and litter box habits. Then they’ll run blood and urine tests.
- Urinalysis: Checks how concentrated the urine is (urine specific gravity), and looks for sugar, blood, bacteria or crystals.
- Blood chemistry: Checks kidney values, blood sugar, liver values, calcium and electrolytes.
- Complete blood count: Looks for infection, inflammation or anemia.
- Total T4: Screens for hyperthyroidism, which is especially important in middle-aged and senior cats.
- Blood pressure: High blood pressure often goes along with kidney disease and hyperthyroidism.
A fresh urine sample helps. Ask your vet for non-absorbent litter to collect one at home, or they can collect a sample at the clinic.
| Service | Typical cost |
|---|---|
| Exam | $55 – $110 |
| Urinalysis | $40 – $100 |
| Senior blood panel with T4 | $150 – $300 |
| Blood pressure check | $30 – $80 |
| Urine culture | $60 – $150 |
For a full breakdown, see how much a cat vet visit costs.
What should I do about my cat drinking a lot of water?
- Never limit water. A cat drinking a lot is usually replacing water they’re losing. Taking the bowl away can make them dangerously dehydrated.
- Offer more bowls. Place water in several spots, and keep an extra litter box available.
- Track it. Write down how much your cat drinks, how often they pee and any weight changes. Your vet will find this very useful.
- Watch appetite. A cat that also stops eating or starts vomiting should be seen the same day.
- Don’t change the diet or add supplements yet. Wait until you know the cause.
Hold off on human medicines and supplements too. A cat that’s drinking more may already have kidney or liver trouble, and acetaminophen (paracetamol) and ibuprofen are toxic to cats and can damage those same organs. For more common signs and what they mean, browse our cat symptoms guides.
Frequently asked questions
How much water should a cat drink a day?
It depends a lot on diet. Cats on wet food get much of their water from food and may rarely drink, while cats on dry food drink more. International Cat Care says a cat drinking more than 100 ml per kilogram of body weight a day is drinking more than usual.
Should I limit my cat's water if they're drinking too much?
No. Cats with kidney disease or diabetes drink more because they're losing more water in their urine. Taking water away can quickly make them dehydrated. Keep water available and see your vet.
Is it normal for a senior cat to drink more water?
Aging alone doesn't make a cat drink more. In a senior cat, increased thirst is one of the most common early signs of kidney disease, hyperthyroidism or diabetes, so it's worth checking.
My cat eats dry food and drinks a lot. Is that normal?
Cats on dry food do drink more than cats on wet food. But a change from their usual amount, or water bowls emptying much faster than before, is still worth a vet visit.
Sources
Written by the CatsMed Team from the sources above. This guide isn’t reviewed by a veterinarian and isn’t a substitute for one. See how we research.
