Why Is My Cat Drinking So Much Water? Causes and When to See a Vet

Published: October 9, 2026

Most owners worry when a cat drinks too little, but drinking too much can matter just as much. A cat that suddenly spends more time at the water bowl, or empties it much faster than before, may be telling you something. This guide explains what counts as "a lot," the common causes, and what to do.

What counts as drinking too much?

Normal intake depends on weight and diet. A healthy cat needs roughly 50–60 mL of total water per kilogram of body weight per day, and a cat on wet food drinks far less than one on dry food. Vets often consider drinking above about 100 mL per kilogram per day to be excessive, which is roughly double the normal total. Most owners cannot measure that precisely, so the practical sign is a clear and lasting change from your own cat's usual habits. You can see what is typical for your cat with the calculator.

Normal reasons for drinking more

• Hot weather or a warm, dry home
• A switch to dry food, or a diet with more salt
• More activity, such as a lively young cat playing a lot
• Nursing: mother cats need more water

If one of these fits and the change is small and short-lived, there is usually little to worry about. Still, watch for other signs.

Health conditions linked to increased thirst

Several illnesses make cats drink and urinate more. The most common are:

• Chronic kidney disease, especially in older cats
• Diabetes mellitus, where the body cannot manage blood sugar properly
• Hyperthyroidism, an overactive thyroid, often seen in middle-aged and older cats
• Urinary tract problems, including infections
• Liver disease and other metabolic problems
• Some medications, such as steroids or diuretics

Only a vet can tell which cause is behind it, and the tests are straightforward.

How the main conditions differ

• Kidney disease: the kidneys lose some ability to concentrate urine, so the cat passes more urine and drinks more to make up for it. It is common in older cats and often develops slowly.
• Diabetes: high blood sugar pulls extra water into the urine. Cats with diabetes often drink and urinate more, and may lose weight while eating well.
• Hyperthyroidism: an overactive thyroid speeds up the body. Typical signs include weight loss, a big appetite, restlessness and more thirst.
• Urinary problems: infections and other issues can change urination habits, and some cats drink more as a result.

These descriptions are only to help you understand why a vet visit is worthwhile. They are not a way to diagnose your cat yourself, since signs overlap between conditions.

Other signs to look for

• Larger or more frequent urine clumps in the litter box
• Weight loss despite a normal or increased appetite
• Changes in appetite, either more or less
• Vomiting, a dull or unkempt coat, or lower energy
• Urinating outside the litter box

The more of these you notice, the more important it is to book a vet visit soon.

Can you measure it at home?

You can get a rough idea if you have only one cat. Measure the water you put in the bowl, then measure what is left 24 hours later, allowing for a little evaporation. If you also feed wet food, remember that it adds water too. In homes with several cats, or with a fountain, it is hard to tell who drank what, so do not worry about exact numbers. Instead, notice whether the bowl needs refilling much more often than before, and whether the litter box has bigger clumps. Those everyday signs are what your vet will find most useful.

Why senior cats need extra attention

The conditions above become more common as cats get older, and cats are very good at hiding illness. Many vets suggest regular check-ups, often with blood and urine tests, for cats in their senior years, so that changes such as increased thirst are caught early. If your older cat has started drinking more, treat it as a reason to book that check-up now, not to wait for the next routine visit.

What to do

1. Note the change. Write down when you first noticed it and how the bowl level, litter box and behavior compare with normal.
2. Check the basics. Has the weather, the food or the routine changed?
3. Book a vet appointment. Do not wait for weeks, especially in a senior cat or if there is weight loss.
4. Bring information. Mention diet, medications, appetite, and litter box changes, and a fresh urine sample if your vet asks for one.

What your vet may do

A typical visit includes a physical exam, a check of weight, blood tests, and a urine test. Depending on the results, the vet may check thyroid levels or blood pressure. Many of these conditions can be managed well, especially when found early, which is the main reason not to ignore increased thirst.

Quick questions

My cat drinks more in summer. Is that okay? A modest increase in heat is normal. A large, lasting change is worth a call.

My older cat is drinking more but seems well. Cats hide illness, and early kidney disease or thyroid problems can look subtle. A check-up is sensible.

Is it the same as not drinking enough? No. Drinking too little points to dehydration risks, covered in our dehydration chart and our guide on why a cat may not drink. See also how much water a cat should drink.

This article is general information, not veterinary advice. If you are worried about your cat, contact your vet.