What are the causes of diarrhea in kittens?

Updated November 21, 2016

Diarrhoea is a common symptom in kittens and generally resolves quickly without veterinary treatment. Persistent diarrhoea may indicate one of several health concerns and requires a veterinary appointment to diagnose and treat the health condition causing the diarrhoea. Kittens frequently experience diarrhoea due to parasites, a change in food, viruses, giardia, drinking milk or eating human food. Less frequently, diarrhoea can indicate kidney or liver disease.


One of the most common causes of diarrhoea in cats is a heavy parasite load. Hookworms and roundworms are two of the most frequent culprits. Other symptoms of worms may include a distended belly and a voracious appetite with stunted growth. Most kittens are routinely dewormed at vet appointments, but if the mother of the litter has parasites, her kittens may acquire them prior to the age at which they'd first see a vet for vaccinations and deworming.

If you suspect that your kitten has worms, see a veterinarian. A simple paste dewormer will clear up most cases.


Giardia is also a type of parasite, but different from worms in that it is a one-celled organism. It causes violent gastrointestinal disturbances, including persistent diarrhoea and vomiting. Kittens most often contract giardia from the faeces of an infected cat. Cats permitted to go outdoors may acquire the parasite from water sources where infected animals have defecated.

Giardia is diagnosed with a fecal exam and most often treated with metronidazone (Flagyl). Some kittens require multiple courses of treatment.

Diet Changes

Some kittens experience temporary or persistent diarrhoea after a change in their diet. A change between dry and wet food will often trigger diarrhoea. Changing brands or formulas of cat food can also have the same effect.

To avoid this symptom, make any diet changes gradually, mixing the old food and new foods over the course of at least a week. If your kitten gets diarrhoea after every food change no matter how gradual, he should see a veterinarian. Kittens raised on a high-quality food with quality animal protein and no corn, wheat or soy tend to have more resilient digestive systems and cope more easily with food changes.

Human Food

Kittens often experience diarrhoea after drinking milk or eating table scraps. After the age of weaning, most cats become mildly lactose intolerant and should not drink milk. If milk must be given, goat's milk, kitten milk replacer or a commercial "cat milk" product should be used. Cow's milk is not healthful for cats.

Table scraps often cause diarrhoea because they are high in fat and contain ingredients the cat isn't used to eating. While lean meats can be a healthful addition to a cat's diet, most table scraps should not be fed. If you would like to give your kitten a treat at mealtime, shred some cooked skinless chicken breast with no seasonings or sauces and place about a teaspoon of it in the kitten's dish. Compost your table scraps instead of sharing them with pets and use the compost to grow catnip in your garden.


Viral infections in kittens may cause diarrhoea. A feline retrovirus infection may cause diarrhoea lasting weeks and unresponsive to any treatment. Viruses don't generally respond to medication, though some new antiviral drugs have shown promising results for seriously ill cats and kittens. In general, it is necessary to let the virus run its course while treating the cat for symptoms that may extend the illness, like dehydration due to diarrhoea. A vet may recommend antibiotics to prevent secondary bacterial infection while the kitten's immune system is weakened by a virus.

Serious Illness

If a veterinarian has ruled out parasites, diet and viral infection as causes of a kitten's diarrhoea, a serious health condition may be to blame. This could include cancer or organ failure, which sometimes present with persistent diarrhoea. Diagnosis may require invasive procedures, up to or including organ biopsy.

Don't worry about these more unusual and life-threatening conditions unless the most common causes of diarrhoea have been ruled out. Organ failure and cancer are very rare in young kittens. Most cases of diarrhoea resolve with time, dietary changes, and antibiotics or deworming.

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