Cats descend from desert animals and are famously bad drinkers — they get most of their moisture from prey (or wet food) and rarely empty a bowl. So when a cat suddenly starts hovering at the water bowl, drinking from the tap, or emptying the bowl overnight, it's worth paying attention. Increased thirst, known as polydipsia, is one of the earliest and most telling signs of several treatable illnesses. Here's what it usually means and when to act.
How much water is normal for a cat?
As a rough guide, a healthy cat needs about 50 ml of water per kilogram of body weight per day from all sources combined. A cat on wet food gets most of that from the food itself and may barely touch the bowl, while a cat on dry food drinks noticeably more to compensate. Because the "normal" amount varies so much, the key signal isn't an exact number — it's a clear, lasting change from your own cat's usual pattern.
Common causes of increased thirst in cats
1. Chronic kidney disease
Very common in older cats. 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 often the very first signs.
2. Diabetes mellitus
Excess blood sugar spills into the urine and pulls water with it, so diabetic cats drink and urinate far more than usual, often while eating more but losing weight.
3. Hyperthyroidism
An overactive thyroid speeds up metabolism in older cats, causing increased thirst, a ravenous appetite, weight loss and restlessness.
4. Urinary tract infection or inflammation
Infections and bladder inflammation can drive drinking along with straining, frequent trips to the litter box, or blood in the urine.
5. Diet and environment
Switching from wet to dry food, hot weather, or a very salty treat can all raise water intake temporarily and harmlessly.
6. Medications
Steroids and some other drugs increase thirst as a known side effect. Mention any new prescriptions to your vet.
Red flags: when to worry
Contact your vet promptly if increased drinking appears with any of these:
- Weight loss, even with a normal or increased appetite
- Peeing much more, larger clumps in the litter, or accidents outside the box
- Vomiting, diarrhoea, or a sudden drop in appetite
- Lethargy, hiding, or a dull, unkempt coat
- Straining to urinate or blood in the urine (this can become an emergency in male cats)
- Bad breath with a sweet or ammonia-like smell
How to help and monitor at home
- Track the amount. Measure how much you put in the bowl and what's left each day for a week so you can give your vet real numbers.
- Encourage healthy hydration the right way. Many cats drink more from moving water — a pet water fountain or a wide, shallow ceramic water bowl can support good hydration while you investigate the cause.
- Note litter box changes. Bigger or more frequent clumps often go hand in hand with increased drinking and are useful clues.
- Don't restrict water. If your cat is thirsty from illness, taking water away can make them dangerously dehydrated. Find the cause instead.
Cats drink more readily from fresh, moving water. A pet water fountain or a set of wide, shallow water bowls encourages steady drinking — helpful for cats prone to kidney and urinary issues.
Shop hydration & health →Which cats are most at risk?
Increased thirst is most significant in cats over seven, where kidney disease, diabetes and hyperthyroidism become common. Overweight cats are more prone to diabetes, and any cat on a dry-only diet lives closer to the edge of dehydration. If your cat fits one of these groups, a lasting jump in water intake is a strong nudge to book a wellness check — early diagnosis genuinely changes outcomes.
Noticed a change? Log the symptom in seconds
MyFurtopia's AI Pet Health Scanner lets you log your cat's water intake, litter box changes and other symptoms to get an instant, vet-informed read on how urgent it is and what to ask your vet. It's free to try.
Download the MyFurtopia AppFrequently asked questions
How much water should a cat drink in a day?
As a rough guide, a healthy cat drinks around 50 ml of water per kilogram of body weight per day from all sources, including food. Cats on wet food drink much less from a bowl because their food is mostly water. A sudden, sustained increase above your cat's normal pattern is what matters most.
What does it mean when my cat suddenly drinks a lot of water?
Sudden increased thirst in cats is one of the earliest signs of kidney disease, diabetes or an overactive thyroid, especially in middle-aged and older cats. It can also follow a switch from wet to dry food, hot weather, or certain medications. Because it can signal serious illness, a lasting increase should be checked by a vet.
When should I take my cat to the vet for drinking too much?
See a vet if the increased drinking lasts more than a few days, or comes with weight loss, increased urination, a bigger appetite, vomiting, lethargy or a dull coat. A simple blood and urine test can usually identify the cause, and early treatment makes a real difference for conditions like kidney disease and diabetes.
This guide is educational and not a substitute for professional veterinary care. If your cat's drinking has changed noticeably or comes with other symptoms, contact your vet.