Why does my cat pee outside the litter box?

The most common bladder problem in cats is an inflamed, painful bladder where the vet finds no stone and no infection. It is called idiopathic cystitis (FIC). Stress plays a big part. The cat suddenly needs to go and it hurts, so it does not reach the box or starts to link the box with pain. It often settles in a few days to about ten days, but it tends to come back.

A male cat has a narrow urethra. Mucus, crystals or small stones can block it. The bladder then fills and hurts, and waste builds up in the blood. Early on, a blocked male may pee tiny amounts in odd places, so it can look like a litter box problem. This is an emergency: see a vet the same day.

Crystals and stones scrape and irritate the bladder, and in males they can block the urethra. There are two common kinds. One often dissolves on a prescription diet; the other usually has to be removed by surgery. Only a vet can tell which it is, with a urine test and an X-ray or scan. Burmese cats seem a little more prone to one kind of stone.

A true bacterial infection is rare in healthy cats under about ten years. It is more likely in older cats and in cats with kidney disease, diabetes or an overactive thyroid. A urine test shows whether it is an infection or a sore bladder without bacteria. That is why antibiotics do not help every cat.

Kidney disease, diabetes, an overactive thyroid and some other hormone problems make a cat drink and pee more. The bladder fills faster than the cat can reach the box, and a box that fills up quickly can put it off. These are more common in middle-aged and older cats. A vet finds them with blood and urine tests.

Arthritis, sore feet, poorer sight or smell and dementia in old age can make it hard to reach the box, step over a high rim or squat. Cats hide pain well, so a puddle right next to the box is often the first sign. A cat with dementia can also forget where the box is, especially at night.

A cat that hurt while peeing, was startled by a loud noise, was ambushed by another pet or was punished near the box may avoid it from then on. The cause may be long gone, but the bad feeling stays.

Common faults are a box too small to turn and squat in, a box not scooped every day, a hood or a liner, and an added scent. A covered box also holds the smell in. A box that looks clean to us can be dirty to a cat. In an owner survey, small boxes and rare cleaning went with more peeing in the house.

Most cats like fine, sandy, unscented clumping litter. Scents, rough pellets, rustling silica crystals, a very deep layer or a sudden change of brand can put a cat off. A new litter mixed in slowly is usually accepted.

A box next to the washing machine, in a busy passage, in a dark room, next to the food bowl or up or down stairs is used less. In a home with more cats, one cat can guard the box so another does not dare to pass. Accidents close to the box suggest the cat can reach it but dislikes something. Accidents far away suggest it cannot reach it easily.

The rule of thumb is one box per cat plus one extra, in different places and on every floor. Homes with more cats have more peeing in the house, probably from crowded boxes and tension between cats. In one study about 70 percent of cats had fewer boxes than the rule.

Soft, absorbent things such as a bed, rugs, clothes, the laundry basket, a dog basket or the doormat are chosen most. Other cats pick something smooth and cool instead, such as the bath, the sink or tiles. You see that especially with a sore bladder. A cat that always pees on the same kind of surface has a preference for that surface.

Cats go back to spots that were peed on before, or where the box used to stand. Even when the first cause, such as a sore bladder or a change at home, is long gone, the habit can stay.

A move, a new cat, dog, baby or housemate, building work, moved furniture, a different daily routine, a long holiday or a strange noise can make a cat uneasy. Stress can also bring on a sore bladder. Even small changes count for a cat, and it feels best with a steady routine.

Tension between cats often looks calm: one cat stares, blocks the way or guards the box. A neighbour's cat in the garden or behind the window can also upset your cat, even when the cats in the house get on well.

Some cats that find it hard to be alone, or that are upset by visitors, pee on your bed or clothes, where your smell is strongest. In one study of cats that struggled with being left alone, peeing outside the box was the most common sign, often on the owner's bed. That is worry, not protest.

Small spots on upright things such as walls, door frames, curtains and furniture are marking. It is often linked to other cats, not being neutered, or stress. Neutered cats sometimes mark too, and a sore bladder can look like marking. Spraying has its own page.