My cat is drinking a lot of water: what it can mean
Cats naturally drink little. So when one starts spending more time at the water bowl, or the litter tray fills with huge clumps, it is almost never because it is hot: it is usually the first visible sign of a disease that is worth diagnosing early.
Why cats drink so little
The domestic cat descends from a desert wildcat that got almost all its water from its prey, which is around 70 % water. It still works that way: it has a weak thirst drive and very efficient kidneys that concentrate urine. A cat that eats mainly wet food can drink very little from the bowl and be perfectly hydrated. One that eats only dry food drinks more, but still not much. That has two consequences: many cats live at the low end of hydration, which encourages urinary problems, and a clear increase in thirst almost always has a medical cause.
How much is "a lot"
As a guide, a cat's total water intake, including what comes in food, is around 50 to 60 ml per kg per day (roughly 25 ml per lb). A 4 kg (9 lb) cat on dry food only usually drinks between 150 and 250 ml a day from the bowl; on wet food, far less. Vets consider it clearly abnormal for a cat to drink more than about 100 ml per kg per day, which for that same cat would be 400 ml. But you do not need to get that far to worry: if you notice they drink quite a lot more than before, stay at the bowl for a long time, seek out taps, glasses or the shower, or there are more clumps or much bigger ones in the litter tray, it is a reason to see the vet.
How to measure it at home
Fill the bowl with a known amount using a measuring jug, for example 500 ml, and measure what is left after 24 hours. Do this two or three days in a row to get an average, and allow for evaporation by leaving a glass with the same amount of water in another room as a reference. If you have several cats it is harder: you can measure the total and watch who drinks, or separate the suspect for a few hours. Also note what they eat and how much wet food they get, and look at the size of the litter clumps. Taking this information to the vet helps far more than "I think they are drinking more".
Cause number one: the kidneys
Chronic kidney disease (CKD) is very common in cats from seven or eight years old and its first sign is usually exactly this: the kidney loses the ability to concentrate urine, so the cat urinates more and drinks more to compensate. Months often pass between that first sign and more obvious ones such as weight loss, vomiting or bad breath. Catching it at this stage means you can start a renal diet, control blood pressure and phosphate, and slow its progress considerably. Modern tests, with creatinine and SDMA in the blood and specific gravity and protein in the urine, allow it to be staged according to the international IRIS guidelines.
Diabetes and hyperthyroidism
Feline diabetes resembles type 2 diabetes in people and is more common in overweight, male, middle-aged cats. The cat drinks and urinates a great deal, eats with a bigger appetite and still loses weight; sometimes they walk on their hocks, with the back legs lower. Hyperthyroidism, typical of cats over ten, causes a ravenous appetite with weight loss, restlessness, yowling, vomiting, an unkempt coat and also more thirst. Both are diagnosed with a simple blood test and both are treatable. In diabetes, if you act early and adjust the diet, some cats go into remission.
Other causes to rule out
In an entire female that drinks a lot, especially after a heat, think of pyometra, an infection of the womb that is an emergency. Liver disease, some kidney infections, high blood calcium (hypercalcaemia) and certain tumours also increase thirst. And some medicines, especially corticosteroids and diuretics, make cats drink more: if your cat is taking anything, tell the vet. Heat or a salty dry food may increase intake a little, but if the change is clear and lasts for weeks, do not put it down to summer.
When it is an emergency
Drinking more is almost always a reason for a booked appointment in the next few days, not an emergency. But there are exceptions. Go the same day if they also vomit, will not eat, are very flat or weak, have breath that smells of acetone or overripe fruit (possible diabetic ketoacidosis), are dehydrated despite drinking, or if she is an entire female with vaginal discharge or a swollen belly. And watch out for the classic mix-up: if a male cat keeps going to the litter tray and hardly any urine comes out, he is not urinating more, he is trying to urinate without success, and that can be a urinary blockage, a life-threatening emergency.
What the vet will do and what it costs
An examination including weight, feeling the kidneys and thyroid, measuring blood pressure and examining the back of the eye, because high blood pressure can damage the retina. Then blood tests with full biochemistry, SDMA, glucose, fructosamine if diabetes is suspected and thyroid hormone (T4) in cats over seven or eight, plus a urine test with specific gravity, glucose, protein and sediment, sometimes with culture. Bring a urine sample if asked: there are non-absorbent litters for collecting it at home. As a guide, the package of consultation, full blood tests and urine comes to around 120 to 250 € in Spain in 2026; blood pressure measurement, 20 to 40 €.
Do not take their water away
It might seem logical: if they drink so much and pee so much, cut the water. That is exactly the opposite of what you should do. A cat that drinks more almost always does so because they need it to make up for what they lose in urine, and if you limit water they become dehydrated, which in a diseased kidney can trigger a crisis. Always leave plenty of fresh water in several places around the home, and if they urinate more, add an extra litter tray and clean it more often. Thirst is controlled by treating the cause, not by restricting water.
Why it pays to go early
The three most common causes of increased thirst in cats, kidney disease, diabetes and hyperthyroidism, have one thing in common: they are treated much better when caught before other symptoms appear. In diabetes, early diagnosis increases the chance of remission; in kidney disease, starting the right diet early and controlling blood pressure lengthens life considerably; in hyperthyroidism, treating it early protects the heart and kidneys. That is why yearly check-ups with blood tests from age seven, and every six months from age ten, are the best health investment you can make in a cat.
A cat drinking clearly more than before is almost never doing it because of the heat: it is the usual first clue to kidney disease, diabetes or hyperthyroidism. Measure the water for a few days, do not restrict it and book a check-up with blood and urine tests.
Educational content from Michipedia, translated from the Spanish original. It does not replace the advice of a vet or a feline behaviour specialist. Every cat is an individual.