A cat with both vomiting and diarrhea is most often dealing with gastroenteritis, a general inflammation of the stomach and intestines. The cause can range from something as simple as eating the wrong thing to infections, toxins, or underlying organ problems. Most mild cases resolve within 24 to 48 hours, but the combination of vomiting and diarrhea together accelerates fluid loss, so dehydration is the immediate concern.
Dietary Causes Are the Most Common
The simplest explanation is that your cat ate something that upset its digestive system. This could be table scraps, a sudden switch to a new food, spoiled food, or something your cat grabbed off the counter. Gastrointestinal signs from dietary indiscretion often come from bacterial contamination, excess fat or grease, or bones. While dietary indiscretion is far more common in dogs, cats do eat things they shouldn’t.
Food intolerance and food allergy are different problems that look similar on the surface. A food intolerance doesn’t involve the immune system and tends to cause purely digestive symptoms. It can happen the very first time your cat eats a particular food or additive. A true food allergy, on the other hand, is an immune reaction to a protein in the food. It usually takes several exposures before symptoms appear, and it may also cause skin itching or hair loss alongside the GI upset.
Parasites, Especially in Kittens
Roundworms are the most common intestinal parasite in cats, affecting 25% to 75% of the cat population, with kittens at highest risk. Kittens can pick up roundworm larvae through their mother’s milk within days of birth, while older cats get infected by eating rodents or ingesting eggs from contaminated environments. Roundworm infections often cause vomiting, diarrhea, and loss of appetite, though some cats carry the infection without visible symptoms.
Giardia, a microscopic parasite spread through contaminated feces, infects fewer than 5% of cats overall but is significantly more common in multi-cat households and catteries. Cats under one year old are most frequently affected. Most cats with giardia show no symptoms at all, but when signs do appear, chronic or recurring diarrhea is the hallmark. Diagnosing giardia requires specific stool testing since the parasite is too small to see with the naked eye.
Toxic Plants and Household Chemicals
If your cat has access to houseplants or a garden, toxin exposure is worth considering. A surprisingly long list of common plants cause vomiting and diarrhea in cats: aloe, calla lilies, daffodils, wisteria, geraniums, holly, irises, and privet hedges all trigger gastrointestinal distress. Some produce relatively mild stomach upset, while others, like iris and wisteria, can cause bloody vomit, bloody diarrhea, or mouth sores.
Cleaning products, antifreeze, and certain essential oils are also culprits. If you suspect your cat ingested something toxic, note what the substance was and how much your cat may have consumed. That information will help your vet act quickly.
Stress Can Trigger GI Symptoms
Cats are creatures of routine, and disruptions to their environment can cause real physical symptoms. Stress-related colitis, which produces sudden diarrhea and sometimes vomiting, commonly follows boarding stays, household moves, new pets or people in the home, construction noise, or even severe weather. The symptoms typically resolve once the stressor passes or the cat adjusts, but they can look identical to more serious problems.
Pancreatitis and Other Organ Problems
When the digestive enzymes produced by the pancreas activate too early, they begin digesting the organ itself, causing pancreatitis. About 50% of cats with pancreatitis will vomit or lose weight, and some develop diarrhea as well. Pancreatitis frequently occurs alongside other conditions in cats, including chronic intestinal disease, liver problems, and diabetes, which can make it harder to pin down.
In older cats specifically, hyperthyroidism and kidney disease are common causes of vomiting and diarrhea. Inflammatory bowel disease (IBD), a condition where the immune system chronically inflames the intestinal lining, can affect cats at any age but is more frequently diagnosed in middle-aged and senior cats. These conditions tend to cause symptoms that come and go over weeks or months rather than appearing suddenly.
Kittens and Senior Cats Face Higher Risks
Age matters when evaluating how serious these symptoms are. Kittens have smaller fluid reserves and less developed immune systems, so dehydration and infection progress faster. Unvaccinated kittens are particularly vulnerable to panleukopenia, a severe and potentially fatal viral infection. Young kittens should never skip meals, so withholding food is not appropriate for them the way it sometimes is for adult cats.
Senior cats are also more prone to dehydration and more likely to have an underlying disease driving the symptoms. Vomiting and diarrhea that would be a minor inconvenience for a healthy adult cat can become dangerous for a 15-year-old cat with compromised kidneys.
How to Check for Dehydration
Dehydration can develop quickly when a cat is losing fluids from both ends. You can check at home by gently lifting the skin between your cat’s shoulder blades and releasing it. In a well-hydrated cat, the skin snaps back immediately. If it stays tented or returns slowly, your cat is likely dehydrated. Other signs include dry or tacky gums (healthy gums feel slick and wet), sunken eyes, and lethargy.
Most cats with gastroenteritis will appear less active than normal, lose interest in food, and may hide. A low-grade fever is also common. These symptoms alone don’t necessarily mean an emergency, but they do mean you should be watching closely.
When These Symptoms Need Urgent Attention
Contact your vet promptly if you notice any of the following: blood in the vomit or stool, symptoms lasting longer than 24 hours without improvement, complete refusal to drink water, extreme lethargy or unresponsiveness, or if your cat is a young kitten, a senior, or has a known chronic condition. Dehydration from combined vomiting and diarrhea can become serious within 24 hours, and cats that are already compromised by age or illness have less margin for error.
What Your Vet Will Likely Do
A vet visit for vomiting and diarrhea typically starts with a physical exam and questions about your cat’s diet, environment, and any possible exposures. From there, a fecal exam checks for parasites and abnormal bacteria. Blood work, including a complete blood count and biochemistry panel, helps evaluate organ function and look for signs of infection or inflammation. If the cause isn’t obvious from initial testing, imaging like X-rays or ultrasound may follow to check for obstructions, masses, or inflamed organs.
Feeding After GI Upset
The old advice of boiling chicken breast and white rice for a sick cat has fallen out of favor. That combination is deficient in more than 10 essential nutrients for cats and isn’t appropriate as anything more than a very short-term stopgap. Veterinary therapeutic diets designed for GI recovery are now the standard recommendation, and your vet can suggest a specific product.
How long your cat needs a special diet depends on the underlying cause. If the problem was something straightforward and treatable, like a parasite or a mild virus, your cat can often return to its regular food as soon as it recovers. If the diagnosis turns out to be pancreatitis, IBD, food allergy, or kidney disease, the dietary change may need to be permanent or long-term.