Daily BiscuitsWhen to call the vet
A cat, especially a male, that strains in the litter box and produces little or no urine, cries when trying to urinate, or repeatedly visits the box may have a urethral obstruction. This is life-threatening within 24 to 48 hours and requires immediate emergency veterinary care.
Source: Cornell Feline Health Center, “Feline Lower Urinary Tract Disease”
Set up the litter boxes properly
At least 1 in 10 cats develops a litter box problem, and it’s one of the top reasons cats end up in shelters. Almost all of it is setup.
- Count: one box per cat, plus one. One cat, two boxes. In different rooms, not side by side.
- Size: at least 1.5× the cat’s body length, about 50 cm. A clear storage tub with a hole cut in the side beats most boxes sold as boxes.
- Litter: unscented, fine-grain, clumping, 3 cm deep. Don’t switch brands in one go.
- Place: away from food and water, easy to reach, with more than one way out. Not next to noisy machines.
- Scoop daily. Wash the box with hot water every 1 to 4 weeks. No strong cleaners.
Going outside the box
Vet first, always. Urinary disease and arthritis are the usual causes. Then look at the list above. Never punish; enzymatic cleaner on the spot.
Covered or open
Cats are split about evenly. Let yours choose. A covered box holds smell in, and cats may skip it until it’s cleaned, so scoop it just as often.
The litter box specification
The 2014 AAFP/ISFM House-Soiling Guidelines set out the litter box basics. A single cat needs two boxes in separate locations; in multi-cat homes the rule of thumb is at least one box per cat plus one (n+1). Each box should be about 1.5 times the cat’s length from nose to base of tail, which for an adult means 50 cm (about 20 inches) or longer; a 2025 preference study found cats chose boxes of at least 50 cm. Litter should be a fine, sand-like, unscented clumping substrate at least 3 cm (1.25 inches) deep. Scoop at least once a day, and wash the whole box every one to four weeks with soap and hot water and no strong chemicals. Cats are about equally divided on covered versus open boxes, so let the cat choose, but a covered box holds smell in and cats may avoid it until it is cleaned. Place boxes away from food and water, in quiet spots away from noisy appliances, with openings not facing each other so a cat can get out and away from an approaching cat.
Source: AAFP/ISFM 2014 Feline House-Soiling Guidelines (JFMS)
Fifty centimetres and clumping clay, measured
With 40, 50 and 60 cm boxes available side by side, 78 cats used the 50 and 60 cm boxes for about 36% of eliminations each and the 40 cm box for 17%. In 46 cats offered three clumping litters, clay drew 258 eliminations, wood 152 and paper 66. In 20 household cats with elimination problems, moving to a box at least 50 cm wide with clumping clay litter increased urination inside the box and reduced house soiling and three kinds of dissatisfied behaviour (digging at the walls, perching on the rim, leaving quickly). A 50 cm box is the threshold; 60 cm adds nothing measurable. This supports the guideline rule of 1.5 times the cat's body length.
Source: Iwabuchi-Inoue, Hattori & Kikusui 2025, Journal of Veterinary Medical Science
Why did he suddenly stop using the litter box?
The order of causes is medical first, stress second, box third. Bladder pain, arthritis and kidney disease make the box hurt or make it hard to reach. Stress from another cat, a move or a new schedule shows up as going outside the box: in a study of colony cats, unusual events such as a change of routine made defecating outside the box nearly ten times more likely. Only after those comes the box itself: too small, too dirty, scented, or somewhere another cat can corner them.
What to do: Vet visit this week. Then add a second box in another room, open, big, unscented, with two ways out. Never punish; clean the spot with enzyme cleaner.
Source: AAFP/ISFM 2014 House-Soiling Guidelines; Stella, Lord and Buffington 2011
House soiling: vet first, and what the stakes are
The 2014 AAFP/ISFM House-Soiling Guidelines are clear that any cat that starts urinating or defecating outside the box needs a veterinary exam before behavioural advice, because urinary tract disease, kidney disease, arthritis and hyperthyroidism are common causes that no amount of box adjustment will fix. Two lab findings are specific red flags: a urine specific gravity below 1.030 (dilute urine) warrants bloodwork, and cats over eight should have their thyroid (T4) checked. The stakes are high: the guideline, citing the National Council on Pet Population Study and Policy, says US shelters euthanise 72% of relinquished cats, many because of house soiling, which is a major reason cats are given up. Stress shows up in the litter box too: in a study of 32 colony cats, unusual events such as a change of caretaker or routine made defecating outside the box 9.8 times more likely (Stella, Lord and Buffington 2011). Never punish, clean soiled spots with an enzyme cleaner and never ammonia, and treat the vet visit as step one rather than a last resort.