Quick answer: A cat drinking much more water than usual may simply have switched to dry food, but lasting increased thirst is a common early sign of kidney disease, diabetes or hyperthyroidism, especially in older cats. Measure how much your cat drinks over 24 hours; International Cat Care says more than 100 ml per kg of body weight a day is too much. See your vet, and never restrict water.
Cats are famously light drinkers, so when yours suddenly seems to live at the water bowl, it is natural to worry. Sometimes there is a simple explanation, like a switch from wet to dry food. But a lasting increase in thirst is also one of the earliest signs of several common illnesses in cats, especially in middle-aged and older cats. This guide explains how much water a cat normally drinks, how to measure it at home, the most common reasons a cat drinks more and when to call your vet.
How much water should a cat drink?
The Cornell Feline Health Center explains that cats need about 4 ounces of water per 5 pounds of lean body weight per day, so an average 10-pound cat needs roughly one cup a day. That total includes water from food. Wet food can contain up to 80% water, so cats on wet food may drink very little, while cats on dry food take in more of their water by drinking.
International Cat Care gives a practical threshold: a cat drinking more than 100 ml of water per kilogram of body weight a day (roughly 1.5 fluid ounces per pound) is drinking more than usual and should see a vet. Vets call increased thirst polydipsia, and it usually comes with increased urination (polyuria).
How to measure your cat’s water intake
Both iCatCare and VCA Animal Hospitals suggest measuring water intake over 24 hours, because it helps your vet judge how serious the problem is:
- Fill every water bowl (and any fountain) with a measured amount of water.
- After 24 hours, measure what is left in each bowl.
- Subtract what is left from what you put in. That is roughly how much your cat drank.
- Repeat for two or three days if you can, and write the numbers down for your vet.
If you have more than one pet sharing bowls, iCatCare suggests keeping them apart for 24 hours, as long as that doesn’t distress them. Other clues are useful too: bigger or more frequent clumps in the litter box, a wetter litter tray, or accidents outside the box.
Why is my cat drinking so much water?
Some reasons are harmless and some need treatment. iCatCare and VCA list these as common causes.
Harmless or temporary reasons
- Diet change. Switching from wet to dry food naturally increases drinking.
- Making up for fluid loss. iCatCare notes that cats may drink more after vomiting or diarrhea, to replace lost water. If the illness continues, see your vet.
- Medications. VCA notes that some drugs, including corticosteroids, diuretics and anti-seizure medicines, can increase thirst. Tell your vet about every medicine and supplement your cat takes.
Chronic kidney disease
Kidney disease is one of the most common causes, especially in older cats. Cornell’s guide to chronic kidney disease states that it affects up to 40% of cats over 10 and 80% of cats over 15. As the kidneys lose the ability to concentrate urine, cats pass more urine and drink more to compensate. Other signs include weight loss, poor appetite, an unkempt coat and lethargy. Early stages often have no other obvious signs, so increased thirst can be the first clue.
Diabetes
Cornell explains that the two most common signs of feline diabetes noticed at home are weight loss despite a good appetite, and increased thirst and urination. Sugar spills into the urine and pulls water with it. Risk factors include obesity, older age, inactivity, being male and steroid use.
Hyperthyroidism
An overactive thyroid is common in middle-aged and older cats. Cornell lists the most common signs of hyperthyroidism as weight loss, increased appetite, and increased thirst and urination. Some cats are also hyperactive, vomit or have an unkempt coat.
Other causes
iCatCare and VCA also mention liver disease, high blood calcium, urinary tract infections and, in unspayed females, a serious uterine infection called pyometra.
| Possible cause | Other clues to watch for | Typical next step |
|---|---|---|
| Diet change to dry food | Otherwise healthy, change started with the new food | Offer more wet food; recheck intake |
| Chronic kidney disease | Weight loss, poor appetite, unkempt coat, older cat | Vet visit: blood and urine tests |
| Diabetes | Weight loss despite a big appetite, more urine | Vet visit: blood and urine glucose |
| Hyperthyroidism | Weight loss, big appetite, restlessness, vomiting | Vet visit: thyroid blood test |
| Medications | Started after a new medicine, such as steroids | Ask your vet before changing anything |
| Pyometra (unspayed females) | Unwell female who was in heat in recent months | Urgent vet visit |
When to see the vet
iCatCare advises that any cat drinking more than usual should be seen by a vet, particularly if intake is over 100 ml per kg per day. Book an appointment if the increase lasts more than a few days or comes with:
- Weight loss, or a bigger appetite with weight loss
- A poor appetite, vomiting or diarrhea
- Lethargy or hiding
- Larger litter clumps or accidents outside the box
Seek urgent care if your cat stops eating, is very weak, or is an unspayed female who seems unwell.
What your vet will do
VCA explains that diagnosis starts with a full history and physical exam. Screening tests usually include a complete blood count, a blood chemistry profile and a urinalysis, sometimes with a thyroid test. iCatCare notes that bringing a urine sample can help; your vet can give you non-absorbent litter for collecting one. Your water-intake notes are useful, so bring them along.
Helping your cat at home
- Never restrict water. A cat drinking more is often making up for water lost in urine. Limiting water can quickly cause dehydration.
- Offer fresh water in several places. Cornell suggests easy-to-reach bowls, making sure no other pet blocks access, and notes that some cats like fountains.
- Keep litter boxes extra clean. More drinking means more urine. iCatCare recommends always having a clean litter tray available to prevent accidents.
- Make rest easy for older cats. Many cats who drink more are seniors. A soft, warm, easy-to-reach bed such as the Teddy Fleece Cat Pad, placed near water and a litter box, saves stiff joints extra trips. A low, cozy hideaway like the Pop-Up Cat Play Tent can also help a cat feel secure. Our senior cat care guide has more tips.
A cozy bed for older cats
Many cats who drink more are seniors. Our soft, washable Teddy Fleece Cat Pad gives them a warm spot that is easy to reach.
Frequently asked questions
How much water should a cat drink a day?
Cornell estimates about 4 ounces per 5 pounds of lean body weight, including water from food, or roughly one cup for a 10-pound cat. Cats on wet food drink less from the bowl.
How much water is too much for a cat?
International Cat Care says a cat drinking more than 100 ml per kilogram of body weight a day is drinking more than usual and should see a vet.
Why is my older cat drinking so much water?
Common causes in older cats include chronic kidney disease, diabetes and hyperthyroidism. All three are treatable or manageable, and early diagnosis helps.
Should I limit my cat’s water if they are drinking a lot?
No. Restricting water can cause dehydration, especially if your cat is losing extra water through urine. Keep fresh water available and see your vet.
Can dry food make my cat drink more?
Yes. Dry food contains much less water than wet food, so cats on dry food drink more. If thirst rose without a diet change, see your vet.
Keep reading
- Senior cat care: how to care for an older cat
- Signs of arthritis in cats
- How to keep an indoor cat warm in winter
- How many hours do cats sleep?
Sources
- International Cat Care: Increased thirst and drinking
- VCA Animal Hospitals: Testing for Increased Thirst and Urination
- Cornell Feline Health Center: Hydration
- Cornell Feline Health Center: Chronic Kidney Disease
- Cornell Feline Health Center: Feline Diabetes
- Cornell Feline Health Center: Hyperthyroidism
This article is general information, not veterinary advice. If you are worried about your cat’s health, contact your veterinarian.
