Cat diarrhea is most often caused by a sudden diet change, stress, or a mild infection, and in those cases it typically resolves within a day or two. But if it lasts longer than 48 hours, recurs frequently, or comes with other symptoms like vomiting or lethargy, something more serious may be going on.
The Most Common Triggers
Switching your cat’s food abruptly is one of the most frequent causes of loose stools. A cat’s digestive system needs time to adjust to new proteins or ingredients, and a sudden swap can cause a few days of diarrhea on its own. This is why vets recommend transitioning food gradually over a week or so, mixing increasing amounts of the new food with the old.
Stress is another reliable trigger. A long car ride, a stay at a boarding facility, a new pet in the house, or even rearranging furniture can produce a brief episode of loose bowels. This type of diarrhea is usually short-lived and clears up once the cat settles back into its routine.
Beyond diet and stress, the list of possible causes gets longer: intestinal parasites, bacterial infections, food allergies or intolerances, inflammatory bowel disease, an overactive thyroid, kidney or liver problems, and in some cases, intestinal tumors. In adult cats, diarrhea that can’t be traced to a dietary change is most likely tied to an inflammatory, infectious, or (less commonly) cancerous process in the gut.
Parasites and Infections
Two of the most common intestinal parasites in cats are coccidia and Giardia. Coccidia rarely causes problems in adult cats, but in kittens it can destroy the intestinal lining and produce mucousy diarrhea along with vomiting and loss of appetite. Kittens typically pick it up by swallowing cysts shed in another cat’s feces, and those cysts can become infectious within just six hours of being deposited. Flies and cockroaches can also carry them.
Giardia spreads the same way, usually between littermates or from a chronic carrier cat. Most Giardia-infected cats actually show no symptoms at all, but when they do, it’s usually acute or chronic diarrhea. Diagnosing Giardia can be tricky because the organism isn’t shed continuously in the stool, so your vet may need to test multiple fecal samples before catching it.
Bacterial infections and viruses, including feline distemper (panleukopenia), can also cause diarrhea. These tend to come on suddenly and are often accompanied by fever, vomiting, and a noticeable drop in energy.
Why Kittens Are More Vulnerable
Kittens face a higher risk of diarrhea for several overlapping reasons. Their digestive tracts and immune systems are still developing, they’re adjusting to solid food for the first time, and they’re socializing more widely with people and animals, which exposes them to new infections. All of this happens at once during weaning.
The bigger concern with kittens is how quickly diarrhea becomes dangerous. Because they have limited energy and metabolic reserves, dehydration and low blood sugar can develop rapidly and seriously affect their health. A kitten with diarrhea that lasts more than a day, or that seems weak or refuses to eat, needs veterinary attention promptly.
Chronic Diarrhea and Underlying Disease
When diarrhea keeps coming back or never fully resolves, it points toward a chronic condition. The two most common in cats are inflammatory bowel disease (IBD) and intestinal lymphoma, a type of cancer that develops in the gut’s lymph tissue. Both cause similar symptoms: ongoing diarrhea, weight loss, decreased appetite, and sometimes vomiting.
Telling these two conditions apart is genuinely difficult, even for veterinary specialists. Ultrasound, endoscopy, and even tissue biopsies under a microscope can look similar in both diseases. Definitive diagnosis often requires a layered approach: first examining biopsy samples for structural patterns, then using specialized staining to identify cell types, and finally running genetic tests to determine whether the immune cells present are cancerous or simply inflamed. This matters because treatment is very different for each condition.
Recurring diarrhea can also signal problems outside the intestinal tract entirely. An overactive thyroid gland, kidney disease, and liver disease can all produce chronic loose stools as a secondary symptom.
How to Check for Dehydration at Home
The biggest immediate risk from diarrhea is dehydration. You can check your cat’s hydration two ways. First, look at the gums: they should be moist and slick. If they feel dry or tacky, your cat is likely dehydrated. Second, try the skin tent test. Gently pinch and lift the skin over your cat’s shoulders, then release it. In a well-hydrated cat, the skin snaps back almost immediately. In a dehydrated cat, it returns slowly or stays “tented” for a moment.
One caveat: older cats often have decreased skin elasticity even when they’re perfectly hydrated, so the skin test is less reliable in senior cats. For them, checking the gums is a better indicator.
What You Can Do at Home
If your cat is an adult, acting normally, eating, drinking, and the diarrhea just started, you can try managing it at home for 24 to 48 hours. The standard approach is a temporary bland diet: boiled white rice mixed with plain boiled chicken breast (no skin, no bones, no seasoning). Mix roughly four parts rice to one part shredded chicken. You can substitute boiled potato or plain pasta for the rice, and low-fat cottage cheese or egg whites for the chicken.
Feed small amounts several times a day rather than large meals. The goal is to give the gut something easy to process while it recovers. After a day or two on bland food, gradually reintroduce your cat’s regular diet over three to four days.
Make sure fresh water is always available. Cats with diarrhea lose fluid fast, and many cats are poor drinkers to begin with. A water fountain or adding a small amount of water to their food can help.
Signs That Need Veterinary Attention
Diarrhea that lasts more than two days, or that keeps recurring even after resolving temporarily, warrants a vet visit. The same goes if you notice any of the following alongside loose stools:
- Blood in the stool (bright red or dark/tarry)
- Vomiting that lasts more than a few hours
- Lethargy or weakness, especially in kittens
- Refusal to eat or drink for more than a day
- Weight loss that you can see or feel
- Signs of dehydration like dry gums or tented skin
Your vet will likely start with a fecal exam to check for parasites and may run blood work to screen for thyroid, kidney, or liver issues. If an infection is identified, treatment is usually straightforward. For persistent cases, imaging or biopsies may be needed to distinguish between IBD and more serious conditions like lymphoma.