Why is my cat drinking so much water?
A cat drinking noticeably more water than usual is rarely nothing. It is one of the more reliable early signs that something is going on internally — commonly the kidneys, diabetes or an overactive thyroid — even when your cat still seems bright in itself. It is worth a same-week vet visit rather than a wait-and-see, and sooner if anything else has changed too.
Get this seen
This is worth a call to your vet rather than waiting to see how it goes, particularly if it has lasted more than a day or your pet is otherwise off-colour.
What actually counts as "a lot"
Most owners notice increased thirst indirectly before they notice it directly: the water bowl needs topping up more often, a cat starts visiting a fountain or tap repeatedly, or the litter tray is heavier and needs changing sooner because there is simply more urine in it. A cat drinking twice its normal amount over a week or two is the pattern worth paying attention to, not one warm afternoon where the bowl runs low.
Diet changes the baseline, so compare like with like. A cat eating mostly wet food gets a good deal of its water from the pouch and drinks very little from a bowl as a result, while a cat on dry kibble alone drinks noticeably more just to make up the difference. If you have recently switched food, give it a week or two before deciding the drinking itself has changed.
The common causes
In cats past about seven or eight, chronic kidney disease is the single most common reason a vet hears about increased drinking, and it tends to creep in gradually rather than appear overnight — which is exactly why owners often say the cat "seemed fine" right up until a blood test. Diabetes is another one to know about, usually alongside a good appetite that does not translate into weight gain, or even weight loss despite eating normally. An overactive thyroid (hyperthyroidism) shows a similar pattern in older cats: eating well, often ravenously, while losing weight and becoming more restless or vocal.
Less common causes include a urinary tract infection, a side effect of a new medication your vet has prescribed, or, in hot weather, a straightforward and short-lived response to genuine heat and activity. None of these should be assumed from the drinking alone, which is exactly why a check is worth doing rather than guessing.
When to get it looked at
A sustained increase in thirst over more than a few days is worth booking a routine vet appointment for that same week, even if your cat seems otherwise completely normal — increased thirst is very often the first thing to change, well before a cat looks or acts unwell. Move that forward to the same day if your cat is also losing weight, off their food, vomiting, unusually lethargic, or drinking so much they seem distressed by it.
A vet cannot tell the difference between these causes by eye. Blood and urine tests are the only reliable way to work out what is actually going on, and catching a change early generally makes it far easier to manage well, whichever of the common causes turns out to be behind it.
What to do while you wait for the appointment
Keep clean water available in more than one spot around the house, and resist any instinct to limit it — restricting water to a cat that is drinking more than usual can be genuinely dangerous and does nothing to address whatever is causing the thirst in the first place. It helps the vet enormously if you can give them a rough sense of scale: how many bowl refills a day, or how much a jug drops by, rather than just "more than before".
A water fountain does not treat anything, but plenty of owners find one useful for exactly this kind of monitoring, since a moving reservoir is easier to keep topped up and easier to judge day to day than a bowl that gets refilled on autopilot. Note down anything else you notice in the meantime too — appetite, energy, weight, litter tray habits — because that detail is often what points a vet toward the right test first.
What can help
Things we stock that owners commonly use alongside a vet’s advice — not a substitute for it.
Cordless Filter-Free Cat Water Fountain 3L
A 3L cordless cat water fountain that runs on batteries with no filter cartridges to replace, so it can sit anywhere in the home away from a socket.
From£58.49
304 Stainless Steel Pet Water Fountain 3.2L
A 3.2L 304 stainless steel fountain that automatically circulates water through a gooseneck spout to keep it fresh. A visible side window shows the water level, so cats and dogs always have clean water.
£36.99
Sensor Cat Water Fountain 2.5L
A 2.5L cat fountain that flows when your cat approaches, keeping water fresh and tempting. A clear level window shows when to refill, and the generous tank meets one cat's needs for several days.
From£43.99
Absorbent Cotton Gauze Swabs for Pets – Pack of 100
Highly absorbent, low-lint cotton gauze swabs produced in clean conditions — a practical first-aid essential available in three size and ply combinations.
From£4.49
Common questions
- How much water should a cat normally drink a day?
- There is no single healthy number, because it depends heavily on whether your cat eats wet or dry food, the weather, and the individual cat. What matters far more than any absolute figure is a genuine change from your own cat's normal pattern — that is what a vet will want to hear about, not a number compared against another cat.
- Could it just be the hot weather?
- It can be, especially during a genuine heatwave alongside more time spent active or outdoors. The test is whether it settles back down once the weather cools — if the increased drinking continues afterwards, or comes with any other change, treat it as worth a vet visit rather than putting it down to the sun.
- My cat is drinking more but otherwise seems completely normal — should I still get it checked?
- Yes. Increased thirst is very often the first sign that appears, well before a cat looks unwell in any other way, which is exactly why so many owners are surprised by what a blood test finds. Bright and eating well does not rule out something worth catching early.
- Can changing my cat's food explain it?
- It can. Moving from a mostly wet diet to dry food removes a lot of the water a cat was previously getting through their meals, so they naturally drink more from the bowl to compensate. Give it a week or two after any food change before judging whether the drinking itself has genuinely increased.
- Is this more likely in older cats?
- Yes, the most common underlying causes — kidney disease, diabetes and an overactive thyroid — are all considerably more common from around seven or eight years old onwards, which is one reason regular senior health checks are worth keeping up even when a cat seems perfectly well in itself.
Related
Sources
Written against guidance published by UK veterinary and welfare organisations. Always confirm specifics with your own vet.
Written by Matt Garnett, who runs Giddy Pets and is a lifelong pet owner — not a vet. This is general information, not veterinary advice, and it cannot replace an examination by the vet who knows your animal. How we write these guides.