First question: is it actually “a lot”?
Before worrying, check the boring explanations. A cat eating dry kibble drinks more than a cat eating canned food — that's physics, not disease. Hot weather pushes thirst up too, and it settles once things cool off (PetMD).
The real signal is change. Most cats visit their water bowl five or six times a day (PetMD). If that suddenly becomes twelve, or the bowl you filled yesterday is empty by noon, something shifted.
How to measure what your cat actually drinks
- Use one bowl. Multiple water sources and multi-pet homes make home tracking unreliable — a single measured bowl is the only honest test (PetMD).
- Measure morning to morning. Put in a measured amount in the morning, measure what's left the next morning, and subtract. Bowls with printed measures or a smart fountain do the job too.
- Watch the litter box. Drinking more means urinating more: heavier clumps, faster-filling boxes. In multi-cat homes this is often the first thing anyone notices (PetMD).
- Log it. A week of notes — amounts, trips to the bowl, appetite, weight — turns a vague worry into something your vet can actually use.
The big four medical causes
If diet and weather don't explain the thirst, PetMD's short list is where vets start:
- Chronic kidney disease. The most common reason an older cat starts drinking and urinating more. Merck notes it affects up to 35% of elderly cats, and excessive thirst and urination are usually the earliest visible signs. Catch it early and treatment has its best chance.
- Hyperthyroidism. Middle-aged and senior cats eat constantly yet lose weight — drinking comes along with it (PetMD).
- Diabetes. Not enough insulin means blood sugar rises and the cat compensates by drinking. Most common in overweight, younger to middle-aged cats, especially on dry food (PetMD).
- Urinary tract infection. Different pattern: small amounts, very often, plus restlessness. A male cat straining to urinate is a medical emergency (PetMD).
Also on the list: liver disease (usually paired with a poor appetite), and medications like steroids or diuretics — ask your vet if a new prescription changed the thirst.
When to call the vet — and what to bring
Any unexplained, lasting increase in drinking deserves an appointment; a passing thirst spike after a food switch or a heat wave does not (PetMD).
Do not restrict your cat's water while you wait — vets need to see the pattern, and withholding water can dehydrate a cat who's already losing fluid. Bring your one-week log. Typical first steps are bloodwork and a urinalysis, which together separate kidney disease from thyroid trouble and diabetes.
Call sooner if the thirst comes with weight loss, a poorer appetite, vomiting, or personality changes in an older cat — that combination is the classic kidney-disease picture (PetMD, Merck).
Frequently asked questions
How much water should a cat drink in a day?
It varies with diet — dry-food cats drink noticeably more than wet-food cats (PetMD). What matters is the pattern: most cats visit a water source five or six times a day, and a sudden jump from that baseline is the thing to report to your vet.
Why is my senior cat suddenly drinking so much water?
In older cats, kidney disease is the most common cause, followed by hyperthyroidism and diabetes (PetMD). Merck notes excessive thirst and urination are typically the first visible signs of chronic kidney disease — which makes this a book-the-visit moment, not a wait-and-see one.
Is a cat drinking a lot of water always a bad sign?
No. Switching from wet to dry food, hot weather, and some medications (steroids, diuretics) all raise thirst temporarily (PetMD). The rule is change plus persistence: a new, lasting pattern that survives a food switch or a cool week earns a vet visit.
Should I limit my cat’s water if she’s drinking too much?
No — never restrict water to “fix” thirst. The extra drinking is a symptom, and cutting it off risks dehydration in a cat whose body is already losing fluid (PetMD). Get the cause diagnosed instead.