Why Does My Cat Drink So Much Water?

When your cat seems glued to the water bowl, it’s natural to worry. Sometimes “more thirst” is just a normal response to diet or weather. Other times, it’s one of the earliest red flags for health issues that are far more manageable when caught early. In this guide, you’ll learn what counts as “too much,” the common—and not-so-common—reasons cats ramp up their water intake, what you can check at home, and how vets get to the bottom of it.

1. How much water is “a lot” for a cat?

Veterinary references often define polydipsia (excessive thirst) using a weight-based threshold. Many clinicians use >100 mL per kilogram of body weight per day as the cutoff (e.g., >400 mL/day for a 4 kg cat). Others flag values above ~45–50 mL/kg/day as suspicious—especially if there’s an obvious change from your cat’s normal pattern. In practice, trends matter: a sustained rise over a few days is more concerning than one thirsty afternoon.

Typical “maintenance” intake for healthy cats often lands around 25–60 mL/kg/day, but this varies with food moisture, ambient temperature, and activity. Cats on dry food tend to drink more to make up for missing moisture; cats on canned diets often drink less because their food already contains ~70–80% water. That means a cat who suddenly seems to drink less after switching to canned food might still be perfectly hydrated.

If your cat’s water intake is drifting upward and you’re not sure it’s normal, jump to section 6 for a simple, accurate way to measure it at home.

2. Normal reasons a cat might drink more

Diet: Dry-fed cats usually drink more; canned-fed cats may hardly visit the bowl. Total hydration (from food + bowl) can be similar, but your perception of drinking can change dramatically with a diet switch. Some research also shows that increasing dietary moisture can raise total water intake.

Heat & activity: Hot days, heated homes, or bursts of play increase evaporative and respiratory water loss, nudging thirst up. (This is one reason to compare today’s intake to your own cat’s baseline over several days.)

New water source: Many cats prefer moving water (fountains) or certain bowl shapes/materials; “novelty” alone can temporarily boost sipping.

Life stage: Pregnant or nursing queens may drink more to support milk production and metabolic needs. Your vet can confirm whether the change fits the life stage. (See section 7 for what a checkup includes.)

If the pattern persists—or you’re seeing other changes like bigger urine clumps, weight loss, or appetite swings—keep reading.

3. When should you worry?

Call your vet promptly if you notice any of the following alongside increased drinking:

• Weight loss, bigger or more frequent pees, or voracious appetite (classically seen with diabetes or hyperthyroidism).
• New lethargy, vomiting, or bad breath with more peeing/drinking (possible kidney disease).
• Senior cats (10+ years) showing a new thirst habit—age raises risk for the “big three” causes (kidney disease, diabetes, hyperthyroidism). Senior cats benefit from exams at least every 6 months.
• Sudden drinking spike over 24–48 hours without an obvious reason (heat, play, diet).

If your cat can’t urinate or is straining/yowling in the box, that’s an emergency unrelated to thirst—seek immediate care.

4. The “big three” medical causes

These three conditions explain a large share of feline polydipsia. Early identification dramatically improves outcomes.

4.1 Chronic kidney disease (CKD)

As kidneys lose their ability to concentrate urine, cats pee larger volumes; thirst rises to keep up—often one of the earliest signs owners notice. Other clues can include weight loss, appetite dips, and lethargy.

How vets check: Physical exam, urinalysis (including urine specific gravity), and bloodwork. Many practices also include SDMA, a kidney biomarker that can rise earlier than creatinine and isn’t inflated by muscle loss. Imaging (ultrasound, X-rays) may follow.

Good to know: CKD is common in older cats but manageable. Early detection allows diet adjustments, blood pressure control, and supportive care that slow progression and enhance quality of life.

4.2 Diabetes mellitus

Persistent high blood sugar causes sugar to spill into urine, pulling water with it (osmotic diuresis). Cats pee more, get thirsty, and often lose weight despite a good—sometimes huge—appetite.

How vets check: Blood glucose, urinalysis (looking for glucose/ketones), and fructosamine (distinguishes true diabetes from stress-spikes). Treatment typically combines insulin with nutrition and weight management.

4.3 Hyperthyroidism

An overactive thyroid revs metabolism, so many cats lose weight, act restless or ravenous, and drink/pee more. It’s especially common in seniors.

How vets check: A physical exam may detect an enlarged thyroid; blood tests (total T4 and, if needed, free T4 or TSH) confirm diagnosis. Treatment options include medication (methimazole), radioactive iodine therapy (I-131), dietary therapy, or surgery.

5. Other (less common) medical reasons to consider

While the “big three” are frequent culprits, vets keep a broader list in mind:

• Diabetes insipidus (DI): Very rare. Either the brain doesn’t make enough antidiuretic hormone (central DI) or the kidneys don’t respond to it (nephrogenic DI). Cats produce enormous volumes of very dilute urine and drink constantly. Specialized testing (water deprivation/ADH response) confirms it.
• Primary (psychogenic) polydipsia: Also rare. After ruling out other causes, some cats simply overdrink; case reports describe confirmation when desmopressin fails to reduce intake.
• High calcium (hypercalcemia): Can blunt the kidney’s concentrating power, leading to PU/PD (plus lethargy, constipation, or urinary issues).
• Liver disease: Advanced hepatic dysfunction can contribute to PU/PD through metabolic changes; bile acid testing can help when liver involvement is suspected.
• Uterine infection (pyometra) in unspayed females: May present with lethargy, GI signs, and sometimes PU/PD—sometimes without obvious discharge. Requires urgent care.
• Medications: Steroids (prednisone/prednisolone) and diuretics commonly increase thirst and urination. If your cat’s water intake rose after a new prescription, call your vet—never stop a medication abruptly.
• Renal tubular disorders and other endocrine issues (e.g., hyperaldosteronism): Uncommon but on the differential list for persistent PU/PD.

6. How to measure your cat’s water intake (accurately!) at home

A careful 2–3 day log is gold for your vet—and for your own peace of mind.

1. Isolate the source. If you have multiple pets or bowls, confine your cat with one bowl for a 24-hour period (or offer a separate bowl you can remove).
2. Use a measuring jug. Fill the bowl with a known volume (e.g., 500 mL). After exactly 24 hours, measure what’s left. Subtract to calculate mL consumed.
3. Adjust for spillage/food. If you feed canned food, note the can’s net weight and moisture content (most is ~70–80% water) to understand why bowl drinking may fall.
4. Normalize to body weight. Divide mL by your cat’s weight in kg to get mL/kg/day. If it’s >~45–50 mL/kg/day consistently, or approaching 100 mL/kg/day, call your vet.
5. Note context. Record diet, treats, weather, activity, urine clump sizes, and any vomiting/diarrhea.

This simple notebook—plus a quick video of your cat at the bowl, if possible—often speeds diagnosis.

7. What your veterinarian will do

A good work-up is stepwise and minimally stressful:

• History & exam: Weight trend, appetite, behavior, palpation of thyroids/kidneys, dental check, hydration status, and blood pressure (especially in seniors).
• Urinalysis (UA): The urine specific gravity (USG) shows how concentrated the urine is; a persistently low USG with increased water intake points to true PU/PD. UA also screens for glucose (diabetes), protein, infection, and crystals.
• Blood tests (“minimum database”): Complete blood count and chemistry panel (kidneys, liver, electrolytes), SDMA for earlier kidney change, T4 for thyroid, and fructosamine if diabetes is suspected.
• Imaging: Ultrasound or X-rays if blood/urine tests suggest kidney, liver, uterine, or other organ involvement.

From there, treatment targets the cause—insulin for diabetes, CKD nutrition/support, thyroid therapy, antibiotics if there’s a kidney infection, etc.

8. What you can do at home to support healthy hydration

• Offer multiple water stations in quiet, cat-preferred spots; keep bowls washed and topped up. Consider a fountain if your cat seems to prefer moving water.
• Leverage food moisture. If thirst alone is the only issue and your vet isn’t concerned, a partial or full switch to canned diets (or adding water to meals when appropriate) can raise water intake without forcing extra trips to the bowl.
• Keep a log. Note water levels, litter clump size, appetite, and weight monthly—weekly for seniors. This catches trends early.
• Schedule regular wellness checks. For cats 10+, plan at least every 6 months; earlier detection of the big three keeps treatment simpler and outcomes better.

9. Quick myths and FAQs

“If I switch to wet food, my cat will stop drinking completely.”

Not necessarily. Many wet-fed cats drink less because they get moisture from food, but some still visit the bowl. What matters is total water intake and your cat’s clinical picture, not whether you see them drink.

“My cat started prednisolone and now drinks oceans—should I worry?”

Steroids commonly increase thirst and urination. Don’t stop the medication on your own; call your vet to discuss dose, duration, and whether monitoring is needed.

“Isn’t hyperthyroidism just an older-cat thing with weight loss, not thirst?”

It’s both. Many hyperthyroid cats have increased thirst/urination plus weight loss and a big appetite. If you’re seeing these together—especially in a senior—book a T4 test.

“Can cats just decide to overdrink?”

Rarely, yes—primary (psychogenic) polydipsia exists, but it’s a diagnosis of exclusion after ruling out the more common medical causes.

10. Bottom line

A cat who’s drinking more isn’t automatically in trouble—but it’s one of the most useful early clues that something’s changing. Start with a 24–72 hour measurement, note any other signs, and check in with your vet—especially for seniors or if intake is consistently high. With a methodical approach, most causes of feline thirst can be identified and managed, often with simple changes that keep your cat comfortable for years.

Sources

• International Cat Care — Increased thirst & drinking; CKD overview. (icatcare.org)
• Cornell Feline Health Center — Hydration; Diabetes in cats. (vet.cornell.edu)
• DVM360 — Polyuria/polydipsia definitions & work-up. (dvm360.com)
• Today’s Veterinary Practice — Stepwise approach to PU/PD; urine specific gravity use. (Today's Veterinary Practice)
• IDEXX — SDMA kidney biomarker (early CKD detection). (idexx.com)
• Merck Veterinary Manual — Renal dysfunction; Diabetes mellitus; Hyperthyroidism; Hypercalcemia; Diabetes insipidus. (merckvetmanual.com)
• AAHA/AAFP Feline Life Stage Guidelines — Senior visit frequency. (AAHA)
• PetMD — Moisture in canned vs. dry diets; Prednisone/prednisolone side effects. (PetMD)
• VCA Hospitals — Steroid & DI client education. (Vca)
• EveryCat Health — Pyometra in cats (signs can include PU/PD). (EveryCat Health Foundation)
• Peer-reviewed nutrition studies — Diet moisture & feline intake/behavior. (PMC)