Cat drinking a lot: when it is the kidneys

It rarely strikes you all at once. More like this: you are topping up the bowl more often than you used to. She sits by the tap, though she never did that before. The litter tray is heavier than it was. And then the question is in the room: is this still normal?

How much is actually normal?

As a rough guide: around 50 millilitres per kilogram of body weight a day. A four-kilo cat therefore needs about 200 millilitres of water daily — not quite a full glass. That surprises many people, because you rarely see a cat drink.

The reason lies in her origins. The domestic cat descends from a desert animal and is built to take in her water with her prey. A mouse is about three-quarters water. A cat that eats mice hardly needs to drink — and her sense of thirst is correspondingly weak.

Why the bowl misleads

That is exactly why the water bowl is a poor measure. Two examples I meet constantly in practice:

The wet-food cat. Wet food is about 80 percent water. A cat living on it covers a large share of her needs through her food and visibly drinks almost nothing. That is no cause for concern — it is the system working as intended.

The switched cat. Change from wet to dry food and a few days later you have a cat who is forever at the bowl. Nothing has gone wrong — the water that used to come with the food now has to be drunk.

So before you start worrying: has anything changed about the food? The warmth? Is the heating on? And has she perhaps been drinking from the watering can, the shower drain or the plant pot for ages, where you simply never saw it?

The better place to look is the litter tray

What goes in is hard to measure. What comes out is not. And because increased drinking in an animal is almost always the consequence of increased urination, not the other way round, the tray is the more honest sign.

Look out for:

• More clumps than usual, or noticeably larger ones.
• Litter that fills up faster — the bag no longer lasts as long as it did.
• Very pale, almost water-clear urine. Concentrated cat urine is a strong yellow and smells distinctly. If it turns pale and nearly odourless, the kidney is no longer concentrating properly.
• Puddles next to the tray or sudden accidents in a cat who was never unclean.

If you want to know for sure: for three days put down a measured amount of water, pour the remainder back into the measuring jug in the evening and note the difference. With several cats in the household that does not work — then what you see at the tray counts all the more.

The four causes I think of first

Increased drinking is not a symptom you watch and wait on. It is a symptom you have checked — because there is almost always one of four conditions behind it, and all four can be found at a single appointment.

Chronic kidney disease. The most common cause in older cats, and not a rare one: in cats aged 15 and over, an estimated 30 to 50 percent are affected. The kidney first loses the ability to concentrate urine. The cat passes more water and has to drink more to make up for it. By the time that is noticed, a considerable part of kidney function is already gone — which is exactly why it pays to look early rather than late.

Diabetes. Excess sugar is passed out in the urine and pulls water with it. Typical is the combination of drinking a lot, urinating a lot and, at the same time, a good appetite — the cat eats and still loses weight. Overweight and neutered male cats are affected more often.

An overactive thyroid. Common in older cats. Everything runs at full speed: she eats more, gets thinner anyway, is restless, sometimes louder than she used to be, the coat looks unkempt. Increased drinking is part of the picture.

Cystitis. Here the picture is different: the cat goes to the tray often, sits for a long time, and little or nothing comes. A male cat who strains and cannot pass urine is an emergency — not tomorrow, but now. That is the one case in this article where you must not wait for the next appointment.

What I ask first on the phone

So that you are prepared, here are the questions I ask, in this order:

• Since when? Days, weeks, or has it only just caught your eye?
• Has anything changed about the food? Brand, variety, wet to dry?
• Is she eating more, the same or less? That already separates a few things: eating more and losing weight points in a different direction from eating less.
• Has she lost weight? Ideally with numbers — the bathroom scales with and without the cat in your arms will do.
• Is she vomiting? Does her breath smell different?
• What does the tray look like? More, larger, paler?

If your cat is also no longer eating properly, the urgency from that article applies — cats must not go hungry for long, regardless of the drinking.

What happens at the practice

It is less dramatic than many fear. Palpation, weight, blood pressure, plus a blood sample and a urine sample. The four causes above can as a rule be told apart with that, and the urine sample is often more important than the blood: it shows whether the kidney can still concentrate.

Collecting urine at home works well, by the way — with a non-absorbent litter from the veterinary practice or the pharmacy. It should be fresh; a few hours old is still fine.

Why I do not only look at the values

If a cat has kidney disease, the treatment is only the beginning. Then comes the part that is talked about less: how do you get more water into a cat who by nature is hardly ever thirsty? Where does the bowl stand, and does it happen to stand next to the food, which many cats dislike? Is there running water somewhere that she finds more interesting than a standing dish? How many trays are there, and where?

These are not side issues. With a condition that cannot be cured but can be managed well over years, it is exactly such everyday questions that decide how the cat is doing. What I mean by that I have described in more detail in my article on holistic veterinary medicine — and where the line runs.