Cat drinking a lot of water: Vet's guide to excessive thirst in cats

cat drinking a lot of water
(Image credit: Getty Images)

If you've noticed your cat drinking a lot of water, it’s hard to know whether you need to be concerned or not. After all, just like in people, there’s lots of variation in how much cats drink normally. 

Some cats just drink a lot, and you might find they run to the tap when you're at the sink or spend a while at their bowl or water fountain. However, excessive thirst can be a sign of an underlying health condition for some cats. 

So, how do you know whether your thirsty cat needs a trip to the vet? What illnesses can cause excessive thirst? And what symptoms might you notice?

How much water should a cat drink a day? 

First of, you might be wondering, 'how do I know if my cat is drinking too much water’? After all, you can’t be sure that your cat is drinking too much if you don’t know how much they should drink.  

Don't worry, though; there is a method to find out. If you can measure how much your cat drinks in a day, your veterinarian will be able to do a simple calculation to decide whether it's excessive. In one day, cats shouldn’t drink more than 100ml of water per kilogram of their body weight. So, a 4kg cat shouldn't drink more than 400ml of water in a day. 

Why is my cat drinking a lot of water? 

There are many reasons why your cat might be drinking a lot of water. Firstly, it could be normal for them. If they have always drunk a substantial amount of water since they were a kitten, it's less concerning than if there is a sudden change in their thirst. 

It's also worth considering whether it's a hot day or whether they’re fed wet or dry food. Cats who are only fed dry food will often have excellent teeth, but they’ll need to drink more than cats who are fed wet food. You can more information on the pros and cons of dry cat food and wet cat food in our vet's guide to dry vs wet cat food. 

However, some medical conditions can cause your cat to drink more, including hormonal conditions like diabetes and hyperthyroidism, kidney disease, and liver disease. 

cat drinking from a water fountain

(Image credit: Getty Images)

Should I worry about my cat drinking a lot of water? 

Cats don’t usually drink very much, so they tend to keep their hydration at an absolute minimum. There’s some recent evidence to suggest that increasing their water intake might keep their kidneys healthy for longer. Remember, you can encourage your cat to drink more using running water like taps or water fountains.

If your cat suddenly starts drinking substantially more, it could indicate a health problem. Excessive thirst can vary depending on your cat's previous behavior. So, it might mean your cat suddenly spends all their time at the water bowl. 

However, for other cats, you might just see your cat drinking, where you never saw them drinking before. If you notice any change in your cat’s thirst, you should make an appointment with your veterinarian.

Is my cat unwell? 

To help determine whether your cat's thirst is normal or a sign of them being unwell, keep an eye out for other symptoms. If your cat is extra thirsty, they’ll probably also use the litter box or pee outside more than normal. 

Conditions that can cause excessive thirst might also cause changes in your cat’s appetite, vomiting, diarrhea, weight loss, vocalization, or even breathing problems. 

So, let's find out what specific symptoms could mean:

My cat is drinking a lot of water and losing weight

If your feline friend is drinking more and losing weight, it might mean that they have hyperthyroidism. Too much thyroid hormone can make your cat really hungry, and they might be more vocal and a bit frantic. Internally, thyroid hormone increases their blood pressure and, over time, can lead to heart failure. 

It’s not just hyperthyroidism that causes increased thirst and weight loss. Conditions affecting the kidneys and liver can cause similar signs, but usually without an increased appetite. 

Diabetes can sometimes cause weight loss, too. So, you can understand why the veterinarian will need to examine your furry friend and may do some tests before they make a diagnosis. 

My cat is drinking a lot of water and has diarrhea

If your cat is drinking a lot and has diarrhea, it might just mean that they are replacing the fluid they have lost in their poop. After all, it doesn’t take long for dehydration to set in if your cat has vomiting or diarrhea. 

However, keep in mind that although diarrhea isn’t a typical symptom of conditions that cause excessive thirst, every cat is different. So, it’s worth seeking veterinary help if your cat has symptoms of being unwell or their usual habits have changed.

Devon Rex kitten digging sand in litter box while being watched by curious brother

(Image credit: Getty Images)

My cat is drinking a lot of water and is always hungry

If your cat seems extra thirsty and is always hungry, they might have hyperthyroidism. You might also notice symptoms like vomiting, weight loss, vocalization, hyperactivity, or changes in their breathing. 

Hyperthyroidism can be treated in various ways, including medication and surgery. Still, first, your veterinarian will need to do some tests to confirm the diagnosis.

My cat is drinking a lot of water and peeing outside their litter tray

If your cat is drinking more and peeing outside of the litter tray, there are a variety of health conditions that could be causing the symptoms. After all, every condition that makes your cat need to drink more will also make them need to pee more often. In addition to diabetes, hyperthyroidism, and kidney and liver problems, it could also be caused by infection or inflammation of the urinary tract.

cat litter box

(Image credit: Getty Images)

My cat is drinking a lot of water and meowing excessively

If your cat is drinking excessively and meowing, it could mean they have hyperthyroidism. This condition can cause cats to be more vocal while becoming more frantic and sometimes on edge. 

This can mean they are more active at times they wouldn't usually be, and sometimes means they're very loud too. Of course, sometimes they’re being more vocal because they feel more hungry and want to be fed, but the vocalizing can also be at random.

When to visit your vet

If you’ve noticed a change in your cat’s drinking behavior, consider whether there are any reasons why they might be drinking more, like warmer weather or a change in food.

If they’re well, it’s also worth keeping an eye on their thirst for a few days to see if it settles and monitoring them for other symptoms. If your cat is unwell, has been drinking more for more than a day or two, or has any other symptoms, you should make an appointment with your veterinarian.


Changes in your cat’s thirst might not seem serious, especially if your feline friend is acting well and has no other symptoms. However, increased thirst could indicate an underlying health problem, and early treatment could make a real difference. So, if you have any concerns about your feline family member’s drinking habits, speak to your veterinarian. 

Dr Hannah Godfrey is a small animal vet with a love of dentistry and soft tissue surgery. She lives in Wales with her partner, son, and their two cats.