My cat pees outside the litter tray: vet first, then the tray
It is the behaviour problem that gets more cats abandoned than any other, and it is almost never what it looks like. A cat does not pee outside the tray out of spite or a tantrum. Either something hurts, something about the tray puts it off, or something at home is stressing it. And that is the order in which to look.
First of all: the vet
Before you change the litter or move the tray, the cat needs to see a vet. A very large share of cats that pee outside the tray have a medical problem: idiopathic cystitis, crystals or stones in the urine, a urinary infection, kidney disease, diabetes or hyperthyroidism, which make them pee more and more urgently, or arthritis, which makes climbing into a high-sided tray painful. If peeing stings, the cat links the pain with the tray and looks for somewhere else, often soft surfaces such as beds, rugs or clothes. However much you change the tray, if there is pain it will not get better. Take a urine sample if you can and explain how long it has been happening and where.
The emergency that cannot wait
There is one situation where you do not wait even until tomorrow: a cat, especially a male, that goes in and out of the tray again and again, strains and produces only a few drops or nothing, cries while trying, licks its genitals a lot or is listless and vomiting. This can be a urethral blockage, which stops the bladder emptying and can be fatal within one or two days through kidney damage and potassium imbalance. Many owners mistake it for constipation. If you see your cat straining in the tray with nothing coming out, call the vet or go to an emergency clinic now. It is one of the most common and most serious emergencies in feline medicine, and the outlook is good if it is treated in time.
Peeing outside is not the same as marking
It is worth telling apart two things that look alike. When the cat squats on a horizontal surface, such as the floor, a rug or the bed, and leaves a normal-sized puddle, it is almost always a toileting problem: it does not want to, or cannot, use the tray. When it stands, tail raised and quivering, against a vertical surface such as a wall, a curtain or a piece of furniture, and leaves a small amount, that is urine marking, a territorial message with different causes and different solutions. Both can happen at once, and both deserve a vet visit, but knowing which one you are seeing tells you a lot about what needs to change.
The litter tray, the usual suspect
If the vet rules out medical problems, the next suspect is the tray itself. What cats reject most: a dirty tray, because their sense of smell is far more sensitive than ours; a small one, when it should ideally be at least one and a half times the cat's length from nose to the base of the tail; high sides for an older cat or one with arthritis; a covered tray that traps smells; or plastic liners that catch the claws. It is also common for there simply not to be enough: the rule is one tray per cat plus one, in different places, not all together in the same corner, because to a cat two trays side by side count as one.
The litter and the location
Many cats reject a new litter, especially scented ones, which smell clean to us and harsh to them. The type most cats accept is an unscented, fine-grained clumping litter, about 3 to 5 cm (1 to 2 in) deep. If you changed litter just before the problem started, go back to the old one. As for location, the tray needs to be somewhere quiet but accessible, away from food and water, and never next to the washing machine, the boiler or a door that bangs open. If something frightened the cat while it was in the tray, it may avoid that spot for a long time. And in a house with several floors, have at least one per floor.
Stress and other cats
In multi-cat homes, the problem is often not the tray itself but the route to it. If one cat watches or blocks the corridor leading to the trays, the other will stop going, however spotless they are. Sometimes tension between cats is so subtle that owners do not notice it: fixed stares, one cat moving aside when the other arrives, one that no longer climbs up to certain places. Spreading trays across several areas, with more than one way out so no cat gets cornered, is often enough. Other sources of stress that trigger peeing outside the tray include house moves, building work, the arrival of a baby, a dog or a new cat, and outdoor cats that can be seen or smelled from the window.
How to clean so it does not happen again
A cat goes back to pee where it smells its own urine, so cleaning thoroughly is part of the treatment. Products containing ammonia, and bleach, are a bad idea: urine contains ammonia, and those smells can invite the cat to mark again. What works are enzymatic cleaners, which break down the organic residue in urine instead of masking it; pet shops sell them for €8 to €20 in Spain. First soak up as much as you can with paper, apply the enzymatic cleaner generously so it reaches as deep as the urine did, and leave it to work and dry on its own. Mattresses and sofas may need more than one go. In the meantime, block access to that spot or change its use, for example by putting food or a toy there.
What you must never do
Rubbing its nose in the pee, telling it off or punishing it not only fails but makes things worse. The cat does not link the punishment with having peed outside the tray, but with you and with that moment, and since stress is one of the main causes of the problem, adding fear is pouring petrol on the fire. It may also learn to hide when it pees, which makes the problem harder to find and to clean. Shutting it in a small room indefinitely as a punishment does not help either. What can help, temporarily and with all its resources, is a quiet room with a very appealing tray, so that it gets back into the habit of using it.
When to get professional help
If the problem continues after the vet has ruled out medical causes, with the trays well placed and the right litter, it is worth consulting a vet trained in clinical behaviour. They will assess the home, the cats and the routines, which often brings to light things you cannot see from the inside, and can judge whether medication is needed as support. The sooner it is tackled, the better: a cat that has been peeing in one spot for months has a deeply ingrained habit. And it is important not to give up, because the vast majority of these cases are resolved or greatly improved once the cause is found. It is a problem with a solution, not a flaw in the cat.
A cat peeing outside the tray is not taking revenge: either something hurts, it dislikes the tray, or something is stressing it. Always see the vet first, and if it is a male straining without passing urine, it is an emergency right now. After that: clean, large trays, one per cat plus one in different places, unscented litter, an enzymatic cleaner and no punishment.
Educational content from Michipedia, translated from the Spanish original. It does not replace the advice of a vet or a feline behaviour specialist. Every cat is an individual.