Constipation in Cats: Signs, Causes, Safe Home Help, and When to See a Vet

Constipation in cats means passing stools less often than normal, or passing small, hard, dry stools with effort, and in most cases it comes down to a cat not getting enough water into its gut. A healthy adult cat usually passes a stool roughly once every 24 to 36 hours, so a cat that has gone 48 to 72 hours without one, or is straining in the tray with little to show for it, is constipated until shown otherwise.

That last phrase matters, because the single most important thing to know about a straining cat is that it might not be constipation at all. This guide starts there, then covers what normal looks like, why cats get blocked up, what is safe to try at home, and what your vet will do if home measures are not enough.

First, rule out a urinary blockage

A cat straining in the litter tray with little or no output could be blocked in the bladder rather than the bowel, and in a male cat that is an emergency that can kill within 24 to 48 hours. From across the room the two look almost identical: the same hunched squat, the same repeated trips, the same faint distress.

The Cornell Feline Health Center describes urethral obstruction as one of the most urgent problems in feline medicine, more common in males because their urethra is longer and narrower, and fatal without treatment as toxins and potassium build up in the blood¹. Constipation, by contrast, is miserable but rarely dangerous in the space of a day.

The practical check is the litter itself. Look for urine clumps. Normal-sized clumps and no stool point towards constipation; no clumps, or only tiny damp spots, point towards the bladder. If you genuinely cannot tell, or the cat is male and crying in the tray, do not wait for a second look: ring the vet now. Our guide to urinary problems in cats covers the signs of a blockage in detail, and it is worth reading before you ever need it.

What normal looks like, and what counts as constipation

Normal for most adult cats is one well-formed, brown, moist stool a day, give or take, and constipation is a clear drop below your own cat’s usual pattern or a change to hard, dry, pellet-like stools. Cats vary, so the baseline that matters is the one you have observed in your own cat while they were well².

The signs owners notice tend to be these:

• Fewer stools, or none for two to three days.
• Small, hard, dry pieces, sometimes left outside the tray because the cat jumped out mid-effort.
• Straining for a long time, sometimes with a small amount of liquid or mucus passed around a hard mass, which can look confusingly like diarrhoea.
• Crying or turning to look at the back end while in the tray.
• Going off food, vomiting, or hiding, which suggests the problem has gone on long enough to make the cat feel unwell.

In a multi-cat house, nobody may notice who has stopped using the tray. If you suspect one cat, a quick check of the trays at the same time each day for a few days, or a spell with that cat in a separate room with its own tray, gives you an answer rather than a guess.

Why cats get constipated

Dehydration is behind most cases of feline constipation, and the cats most at risk are older cats with kidney disease, cats eating mainly dry food, overweight or inactive cats, and cats with sore joints. When the gut is short of water, the colon pulls more fluid out of the stool, which then dries, hardens, and becomes harder to move.

• Chronic kidney disease. Failing kidneys let more water out as urine, leaving the body, and the colon, short. It is one of the most common conditions in older cats and it hides for a long time: blood creatinine often only rises reliably once about 75 percent of kidney function has been lost³. International Cat Care lists constipation among the problems linked to the dehydration CKD causes⁴.
• A mainly dry diet. Dry food is around 10 percent water against roughly 70 to 80 percent for wet food, and cats evolved to get most of their water from prey rather than from a bowl⁵.
• Arthritis and pain. Squatting to pass a hard stool hurts a cat with stiff hips or a sore back, so some hold on, and the longer they hold on the harder it gets. A high-sided tray makes it worse. Our guide to arthritis in cats covers the quiet signs.
• Excess weight and inactivity. Roughly 1 in 2 pet cats are overweight or obese, and a less active cat has a slower gut and more difficulty reaching round to groom⁶.
• Hair and other indigestible material. Heavy grooming, a long coat, or a cat that chews string, grass, or bones can bulk up the stool.
• Tray aversion and stress. A dirty tray, a new litter, a tray in a busy spot, or a bullying housemate can make a cat put off going.
• Less common causes. Narrowing of the pelvis after an old fracture, nerve problems, some medications, and masses in the bowel are all on the vet’s list for a cat with repeated episodes.

Safe things to try at home

For a single mild episode in a bright, eating, comfortable cat, the safe home measures are all about moisture and access: more water in, an easier tray, and gentle activity. Anything medicinal belongs to the vet.

Start with the water. A cat needs roughly 50ml of water per kilogram of body weight a day, so about 200ml for a typical 4kg cat, and most of that should ideally arrive in food rather than from a bowl⁷. In practice:

• Feed wet food, or move a dry-fed cat towards a mix. Make the switch gradually over about 7 days so the change itself does not upset the gut.
• Add a spoonful of water to each wet meal and mash it in. Most cats accept it without noticing.
• Spread water around the house: several wide bowls away from food and litter, and a fountain if your cat likes running water. Our guide to getting a cat to drink more water has the tricks that work.
• Make the tray easy: a low entry for an older cat, clean litter, and a quiet spot.
• Encourage movement with short play sessions, which help a sluggish gut along.

What not to do matters just as much. Never give a cat a human laxative, a stool softener from your own cupboard, or a pharmacy enema: some phosphate enemas made for people can cause a severe and sometimes fatal salt imbalance in cats. Do not force oil or paste into a reluctant cat, which risks it going down the windpipe. If the moisture changes have not produced a normal stool within a day or two, the next step is a phone call, not a stronger remedy.

When constipation needs a vet

Ring your vet the same day if your cat has passed nothing for 48 to 72 hours, is straining repeatedly, is vomiting or off food, seems painful or lethargic, or has had constipation before. A kitten, a cat with a known illness, or a senior cat should be seen sooner, because they have less in reserve.

Senior cats deserve particular attention. From around 11 years old a cat counts as senior, and the AAFP recommends check-ups every 6 months from that age rather than once a year⁸. Constipation is often one of the first visible signs of the dehydration that comes with early kidney disease, so in an older cat it is worth treating as a reason to book bloods rather than as a standalone niggle.

Recurrent constipation also has a risk of its own. Each time a hard mass sits in the colon it stretches the muscle wall, and repeated or prolonged episodes can lead to megacolon, where the colon loses its ability to contract and push stool along. Catching the pattern early, and fixing what is driving it, is far easier than managing megacolon later.

What the vet will do

Expect a physical examination, including a gentle feel of the belly, which usually confirms a hard colon, and then treatment to clear the blockage and blood tests to find the cause. An X-ray shows how much stool is present and whether the colon is enlarged or the pelvis narrowed.

Treatment depends on how backed up the cat is:

• Mild cases are often managed with fluids under the skin, a cat-safe stool softener such as lactulose, and dietary changes the vet will tailor.
• Moderate cases may need a cat-safe enema given at the clinic.
• Severe cases, where the stool has become a hard mass, usually need the cat sedated or anaesthetised so the colon can be emptied gently by hand, along with intravenous fluids.

Long-term management is aimed at the cause: treating dehydration and kidney disease, pain relief for arthritis, weight loss for an overweight cat, and often a high-fibre or highly digestible diet with a daily softener. Bloods and a urine test usually check kidney function, thyroid, and glucose, because all three affect hydration in older cats³. For the small number of cats with megacolon that does not respond to medical treatment, surgery to remove the affected section of colon is an option, and most cats cope well afterwards. If kidney disease turns out to be behind it, our guide to kidney disease in cats explains the stages and what comes next.

A note from Hannah

Marmalade’s constipation crept up on us in his last couple of years, after the kidney disease and the arthritis had both been found. He started going every two or three days instead of daily, and what he did leave was small and hard, sometimes on the mat beside the tray. I only spotted the pattern because I was already writing his water intake in the notebook by his bowl, and I started adding a tick for tray days. Three weeks of ticks showed my vet exactly what was happening. She put it down to the dehydration that comes with failing kidneys plus a cat who found squatting uncomfortable, and the fix was unglamorous: water mashed into every meal, a second fountain upstairs, his pain relief adjusted, and a daily softener she prescribed. He was back to most days within a fortnight. The lesson I would pass on is that, in an older cat, the tray is a health record. Glance at it daily and you will see trouble long before it becomes a crisis.

This guide is general information, not advice about your own cat. If your cat is straining, has not passed a stool for two to three days, or seems unwell, speak to your own vet: they can examine your cat, find the cause, and treat it safely.