Why Does My Cat Have Diarrhea?

What it usually means

Diarrhea happens when food moves through the intestines too quickly for water and nutrients to be absorbed, so stools come out loose, watery or more often than usual. Cornell lists the most common short-lived triggers as a sudden change in diet and stress, such as a car trip, boarding, a move or a new pet. Eating something unusual, like table scraps, spoiled food or a houseplant, is another frequent cause.

Parasites such as roundworms, hookworms, giardia and coccidia are common, especially in kittens and cats from shelters. Food intolerance and food allergy can cause on-and-off diarrhea. In adult cats with recurring or long-lasting diarrhea, VCA and Cornell point to causes such as inflammatory bowel disease, infections, hyperthyroidism, kidney or liver disease, pancreatic problems and intestinal lymphoma, which is why ongoing diarrhea needs testing.

Diarrhea in kittens

Kittens get diarrhea more often than adults because their gut is still adjusting to solid food and they are more likely to carry parasites. A new kitten that has just moved home, changed food and been through a vet visit may well have soft stools for a day or two from the stress and the new diet alone.

Kittens also have far less reserve than adult cats. Cornell warns that a very young kitten can become seriously ill within hours of not eating, and diarrhea drains fluid fast. Call your vet the same day for any kitten with diarrhea that is also quiet, not eating, vomiting or under about eight weeks old. Viral infections such as panleukopenia are a particular risk in unvaccinated kittens and can be fatal.

When to call your vet today

VCA advises a vet visit if diarrhea has not improved within two days, or sooner if it is severe, frequent and watery, or if your cat also has vomiting, a poor appetite, weight loss, a fever, belly pain or weakness. Cats with existing conditions such as kidney disease, diabetes or hyperthyroidism should be seen earlier.

Call as well if the stool contains fresh red blood or a lot of mucus, if your cat is straining repeatedly in the litter box, or if diarrhea keeps coming back every few weeks. Repeated straining can also be a sign of constipation or a urinary problem, and it is easy to mistake one for the other from the outside.

When it's an emergency

Get your cat seen immediately, at your vet or the nearest emergency vet, if you see black, tarry stools, large amounts of blood, profuse watery diarrhea, collapse, extreme weakness, pale gums, or signs of dehydration such as sunken eyes, dry or tacky gums and skin that stays tented when gently lifted. A kitten with diarrhea and vomiting together should also be treated as urgent.

If you think your cat has eaten something toxic, such as a lily, a human medication or a household chemical, call ASPCA Animal Poison Control at (888) 426-4435 or the Pet Poison Helpline at (855) 764-7661 (a fee may apply) and head to a vet. Bring the packaging or a photo of the plant.

What you can safely do at home

For an adult cat that is bright, eating and otherwise normal, you can watch for a day or two. Make sure fresh water is always available, because dehydration is the main risk; VCA puts this first. Keep the litter box very clean so you can see what is happening, and note how often your cat goes, what the stool looks like and whether there is any blood or mucus.

Do not give any human anti-diarrhea medicine. Some contain ingredients that are dangerous to cats. Ask your vet before starting probiotics or supplements, as VCA notes quality varies widely. If you recently changed food, ask your vet whether to go back to the old one. Your vet may recommend a short spell on a veterinary gastrointestinal diet, then a gradual return to the usual food over about a week.

What the vet will likely check

Your vet will ask when it started, how often your cat goes, what the stool looks like, any diet changes, stress, plants or toxins, and whether other pets are affected. They will examine your cat, check hydration and weight, and usually ask for a fresh stool sample to look for parasites. Bringing a sample in a clean, sealed bag from that day saves time.

For mild cases, treatment may be deworming, a bland diet and fluids. If diarrhea is severe or long-running, VCA describes further tests including bloodwork, specialized stool and DNA tests for infections, x-rays, ultrasound and sometimes endoscopy with biopsies. Cats with chronic diarrhea often do well on a long-term prescription diet or medication once the cause is known.

Prevention

Change foods slowly, mixing the new one in over seven to ten days. Avoid feeding table scraps and keep garbage, houseplants and cleaning products out of reach. Keep your cat on a parasite control plan your vet recommends, and have new kittens dewormed and vaccinated on schedule, which protects against panleukopenia.

Reduce stress where you can around moves and new pets with a quiet retreat room and a steady routine. Keep up yearly checkups, twice a year for older cats, so that conditions like hyperthyroidism and kidney disease are found before they cause problems. If your cat has had diarrhea before, keeping a short diary of foods and episodes helps your vet spot patterns.

This page is general information, not veterinary advice, and it cannot replace an examination by the vet who knows your pet.