"My cat is drinking a lot more water than usual"

Excessive thirst in cats almost always signals something internal — not a quirk or a phase

Cats are not naturally big drinkers. Unlike dogs, they evolved in arid environments and are physiologically designed to extract much of their water from prey. When a cat begins drinking noticeably more than usual — vets call this polydipsia — it means the body is losing water faster than normal, or the kidneys are no longer concentrating urine efficiently, and the brain is compensating by triggering intense thirst. Something is causing that shift, and in the vast majority of cases, it is one of three conditions: diabetes mellitus, chronic kidney disease (CKD), or hyperthyroidism. Less commonly, the cause may be a urinary tract infection, liver disease, Cushing's disease, or certain medications like steroids.

These three leading conditions — diabetes, CKD, and hyperthyroidism — share an important characteristic: they are all progressive, they all worsen without treatment, and they are all significantly more manageable when caught early. A diabetic cat diagnosed and stabilised in the early months of the disease has a very different prognosis from one who goes undiagnosed for a year. Kidney disease in particular advances through stages; a cat in stage 1 or 2 CKD can often be supported for years with the right diet and monitoring, while a cat reaching stage 4 has far fewer options. Early action genuinely changes outcomes here.

The one thing the evidence consistently shows is this: excessive thirst in cats does not resolve on its own when it has an underlying cause. If your cat has been drinking noticeably more for more than a week, the appropriate next step is a veterinary blood panel and urinalysis — not a wait-and-see approach. These tests are inexpensive relative to the cost of delayed treatment, and they will almost certainly give you a clear answer.

Increased thirst doesn't always look the same — which version are you seeing?

The underlying cause often shapes how the problem first presents itself, and recognising your specific pattern can help you give the vet more useful information.

The three most likely causes all worsen silently — and all respond to early treatment

It's tempting to wait and see whether a cat's increased thirst settles down on its own. Sometimes it does — a hot week, a temporary stressor, or a recent change in diet can cause a short-lived increase that normalises within a few days. But if the change has persisted beyond one to two weeks, or if it's accompanied by any other symptom — weight change, lethargy, altered appetite, changes in litter box use — the probability of a benign, self-resolving cause is low. The three conditions most likely responsible (diabetes, CKD, hyperthyroidism) cause no pain in their early stages, which means a cat can look and act reasonably normal while the disease quietly advances. By the time other symptoms become obvious, the disease is typically in a more advanced stage where treatment is both harder and more expensive.