How much water should a cat drink per day?

Most cats drink roughly 50 ml per kg bodyweight daily — about 200–250 ml for a 4–5 kg cat. Drinking noticeably more than usual for several days warrants vet blood and urine tests.

Is wet food enough water for cats?

Wet food provides much of daily fluid needs. Cats on dry kibble only often drink more from the bowl — but a sudden increase still needs investigation, not dismissal as normal for dry food.

When is increased thirst an emergency?

Extreme lethargy, vomiting, collapse, or not eating with heavy drinking needs same-day care. Diabetic cats can develop ketoacidosis — an emergency.

Cat Health

Why Is My Cat Drinking So Much Water UK? Polydipsia Causes

Published 25 June 2026Last updated 25 June 20263 min read

Quick answer

Sudden or gradual increase in drinking often means illness in cats — especially kidney disease, diabetes, or hyperthyroidism. Cats hide disease well; polydipsia is an early clue. Book vet blood tests and urinalysis if your cat's water bowl empties faster than usual for more than a few days.

How much is too much?

According to International Cat Care, average intake is about 50 ml per kg per day — variable with diet.

Cat weight	Approximate normal daily intake
3 kg	~150 ml
4 kg	~200 ml
5 kg	~250 ml

Wet food diets supply much fluid — bowl drinking may look low. Dry food only increases visible drinking — but change from your cat's normal matters more than a textbook figure.

How to measure at home

Fill bowl to a marked level each morning
Refill only when empty and note volume added for 2–3 days
Tell your vet the totals and diet type (wet vs dry)

Common causes in UK cats

Chronic kidney disease (CKD)

Very common in cats over 10. Damaged kidneys lose concentrating ability — cats drink more to compensate.

Other signs: weight loss, poor coat, reduced appetite, vomiting. See Kidney disease in cats.

Diabetes mellitus

Middle-aged and older overweight cats are at risk. Excess thirst with increased appetite and weight loss is classic.

Untreated diabetes can become diabetic ketoacidosis — emergency with vomiting and collapse.

Hyperthyroidism

Overactive thyroid in senior cats increases metabolism — drinking, hunger, and activity rise; weight may still drop.

See Hyperthyroidism in cats.

Urinary tract disease

FLUTD and infection sometimes alter drinking — often with straining or accidents.

Liver disease and other conditions

Less common but included in vet work-up.

Medication

Steroids and some drugs increase thirst — expected side effect; discuss with prescribing vet.

When drinking increases without other signs

Early CKD and hyperthyroidism may show only polydipsia initially. Do not wait for collapse — senior cat checks from age 7–10 catch these earlier.

Vet work-up

Expect:

Blood tests — kidney values, glucose, thyroid hormone
Urinalysis — concentration, glucose, infection
Blood pressure — common with kidney and thyroid disease

Treatment depends on diagnosis — many conditions are manageable when caught early.

What not to confuse

Hot weather — mild increase possible; should normalise indoors with shade
New dry diet — gradual increase; compare to baseline after diet change
Pregnancy or lactation — queens need more fluid — vet supervised

Dogs with increased thirst differ — see Dog drinking excessive water.

Sources & further reading

Facts in this guide are rewritten in plain English from publicly available UK advice. We name the organisation where a specific point comes from their guidance. Links below go to the original pages — use them to read the source material directly.

PETHEALTH+ is independent. These organisations do not sponsor, approve, or partner with this website. Guidance checked against sources listed below (last updated 2026-06-25).

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Frequently Asked Questions

Why is my cat drinking so much water?: Increased thirst (polydipsia) commonly indicates chronic kidney disease, diabetes mellitus, or hyperthyroidism in UK cats — especially over eight years old. Less common causes include urinary tract infection, liver disease, and certain medications.
How much water should a cat drink per day?: Most cats drink roughly 50 ml per kg bodyweight daily — about 200–250 ml for a 4–5 kg cat. Drinking noticeably more than usual for several days warrants vet blood and urine tests.
Is wet food enough water for cats?: Wet food provides much of daily fluid needs. Cats on dry kibble only often drink more from the bowl — but a sudden increase still needs investigation, not dismissal as normal for dry food.
When is increased thirst an emergency?: Extreme lethargy, vomiting, collapse, or not eating with heavy drinking needs same-day care. Diabetic cats can develop ketoacidosis — an emergency.