Last updated: October 3, 2026
Cat Health
Cat Drinking a Lot of Water
A cat that suddenly seems thirsty all the time, and is peeing more too, is telling you something. Here is what counts as excessive drinking, roughly how much water is normal, the three common causes vets look for, and when to make the call.
This guide is general information, not veterinary advice. Every cat is different. If your cat is unwell or you are worried, contact your veterinarian, who can examine your cat and give advice for their specific situation.
Call your vet or an emergency clinic now if your thirsty cat also has any of these
- Marked lethargy, weakness, or collapse
- Repeated vomiting, or refusing to eat
- Straining in the litter box or producing little or no urine
- Rapid breathing, disorientation, or a sweet or unusual smell on the breath
Heavy thirst combined with any of these can signal a serious problem such as advanced kidney disease or a diabetic crisis, and cannot wait for a routine appointment.
What Counts as Excessive Drinking?
Vets call abnormally increased thirst polydipsia. As a rough reference, a healthy cat takes in about 40 to 60 ml of water per kilogram of body weight per day, and that figure includes the moisture in food, not just what comes from the bowl. For a typical 4 to 5 kg cat that is roughly 200 to 300 ml a day from all sources. Drinking that is persistently above about 100 ml per kg per day is generally considered excessive and worth investigating.
Diet makes a big difference to what you see. Wet food is around three-quarters water, so cats on wet food get most of their intake from meals and may hardly use the water bowl. Cats on dry food have to make up the difference by drinking, so they naturally visit the bowl more. Because of that, the most useful signal is not a single number but a change from your own cat’s normal, especially if it comes with more urine in the litter box.
The Three Classic Causes of a Genuinely Thirsty Cat
When increased thirst is medical, these are what vets check for first
Chronic kidney disease
As the kidneys lose their ability to concentrate urine, cats pass more dilute urine and drink more to keep up. Increased thirst and urination are among the earliest signs, often before weight loss or a poor coat appear. It is common in older cats and is diagnosed with blood and urine tests.
Diabetes
When blood sugar runs high, excess glucose spills into the urine and pulls water with it, so the cat urinates more and drinks more to compensate. Increased appetite alongside weight loss is a common pattern. Diabetes needs veterinary diagnosis and ongoing management.
Hyperthyroidism
An overactive thyroid speeds up the whole body. Many affected cats drink and urinate more, and often lose weight despite a strong appetite, sometimes with a fast heart rate or restlessness. It is most common in older cats and is confirmed with a blood test.
The common thread: more peeing
All three of these conditions increase urination as well as thirst, which is why a cat that is drinking a lot and peeing a lot deserves a vet visit with urine and blood tests. These illnesses cannot be told apart at home, and each is more manageable when caught early.
Normal vs Excessive Drinking: A Reference
Use this as a starting point, not a diagnosis. Your vet can confirm what is normal for your cat.
| Pattern | What it often looks like | What to do |
|---|---|---|
| Normal drinking | Roughly 40 to 60 ml per kg of body weight per day, including moisture from food. Cats on dry food drink noticeably more from the bowl than cats on wet food. | No action needed. Keep fresh water available and note your cat’s usual pattern so you can spot a change. |
| Mild or short-term increase | A little more drinking during hot weather, after exercise, or after a switch to dry food | Often normal. If the increase lasts more than a few days or has no obvious reason, mention it to your vet. |
| Excessive drinking (polydipsia) | Persistently more than about 100 ml per kg per day, emptying the bowl fast, seeking water from taps or bowls, and usually larger or more frequent urine clumps in the litter box | Book a veterinary exam with urine and blood tests. Increased thirst plus increased urination is a common early sign of illness. |
| Thirst with warning signs | Heavy drinking alongside lethargy, vomiting, not eating, or weight loss | Contact your vet promptly, or an emergency clinic if your cat is very unwell, rather than waiting. |
How to Tell If Your Cat Really Is Drinking More
Impressions can be misleading, so a rough measurement helps. Put a known amount of water in the bowl, limit other water sources for a day where you safely can, and check what is left after 24 hours, allowing a little for evaporation. Weighing the bowl before and after is even more accurate, since one millilitre of water weighs about one gram.
In a multi-cat home this is harder to pin to one cat, so watch the indirect signs instead: a bowl that empties faster than usual, larger or more frequent clumps in the litter box, or a cat that starts drinking from taps, sinks, or unusual spots. Jotting down what you notice, and for how long, gives your vet a useful head start.
When to See a Vet
A brief rise in drinking during hot weather, after play, or just after switching to dry food is usually nothing to worry about. Book a veterinary appointment if the increased thirst lasts more than a few days, has no obvious reason, or comes with increased urination, weight loss, a bigger or smaller appetite, low energy, or a change in coat. For the emergency signs listed at the top of this page, do not wait for an appointment.
Because increased thirst is a shared early sign, your vet will usually run urine and blood tests to sort between the common causes. You can read more about each one in our guides to chronic kidney disease in cats, feline diabetes, and cat hyperthyroidism. These are starting points for a conversation with your vet, not a substitute for an exam.
Frequently Asked Questions About Cats Drinking a Lot of Water
Common questions about increased thirst in cats and when it matters
Why is my cat drinking so much water?
A short-term increase can come from hot weather, more activity, or a change to dry food, since dry food contains far less moisture than wet food. When the increase is persistent, the three classic medical causes in cats are chronic kidney disease, diabetes, and hyperthyroidism. All three tend to raise both thirst and urination, so a cat that is drinking a lot and peeing a lot should be seen by a vet for urine and blood tests to find the cause.
How much water should a cat drink?
A rough guide is about 40 to 60 ml of water per kilogram of body weight per day, and that total includes the moisture your cat gets from food. So a 4 to 5 kg cat needs roughly 200 to 300 ml a day from all sources. Cats eating wet food get much of that from their meals and may barely touch the bowl, while cats on dry food drink more visibly. Consistently drinking well above this range, or a clear change from your cat’s normal, is worth a vet check.
My cat is drinking a lot of water and peeing a lot, is that serious?
Increased thirst together with increased urination is one of the most useful early warning signs in cats and should not be ignored. It is a common feature of chronic kidney disease, diabetes, and hyperthyroidism. None of these can be diagnosed at home, and they are more manageable when caught early, so the safe step is a veterinary appointment with a urine test and blood work rather than waiting to see if it passes.
How can I measure how much my cat is drinking?
Measure a known amount of water into the bowl, keep other water sources closed off for the day if you can, and measure what is left after 24 hours, allowing a little for evaporation. In a multi-cat home this is harder, so watch for indirect signs instead: an emptying bowl, heavier or more frequent clumps in the litter box, or your cat drinking from taps and unusual places. Bring your numbers or observations to your vet, as they help guide testing.
Explore More Cat Health Guides
Understand your cat's symptoms and know when to call the vet.
Free cat printables
Keep these cat care guides handy
A rotating selection of practical cat guides chosen from our free printable library.Kitten Growth Chart
Week-by-week weight and development milestones.
Cat Feeding Guide
Portions by weight, age, and life stage.
Kitten Calorie Guide
Calorie targets by kitten age and weight.