Causes of kitten diarrhea and when it’s better to call a vet

The gastrointestinal tract of small puppies, kittens, and other (even human) babies is still developing, as well as their immune system. That’s why even small changes in their environment or diet can lead to an upset tummy, diarrhea, and other bowel problems.

I’ve already talked about diarrhea in puppies, so let’s talk about kitten diarrhea now.

Diarrhea is not a disease, it’s actually a symptom, where the pet frequently releases liquid stools.

When it comes to kitten diarrhea, it can be caused by a simple change in the diet. However, it can also be a sign of a more serious underlying condition. On top of that, small babies (animals and humans alike) are prone to dehydration, and losing bigger amounts of liquids can be dangerous.

So let’s take a closer look on what are the main causes of kitten diarrhea, how can you help your darling at home, and when it’s better to call a vet.

While I am a veterinarian, this article is not intended to replace professional veterinary advice. If you have any medical concerns about your pet, consult your vet immediately. Always seek professional assistance if you are unsure of your pet’s health.

This post may contain affiliate links, which means I may receive a commission, at no extra cost to you, if you make a purchase through a link. Please see my full disclosure for further information.

portrait of a small kitten

How to know if your kitten has diarrhea

If your cat poops outside or goes to her litter box and covers her poop thoroughly, you may initially not notice that something is not right.

Often you can see stains on the fur around her back end and/or on her paws, that’s a big hint that something’s going on 🙂

In case your kitty is still using her litter box, the smell often becomes strong and you can find covered puddles instead of formed stool inside.

Kitten stool is a bit softer than that of an adult cat. If it’s shapeless, mushy, or liquid, your kitten has diarrhea.

Kitten stool can change color depending on her diet – light brown to brown is normal.

If the stool is greenish, black, yellow, or has blood in it, call your vet.

If your cat’s stool is formed but has white flecks in it, call your vet and be careful when handling your kitty, since she probably has worms.

Kitten diarrhea and cat stool color infographic
Why is the color of your cat’s stool important

The most common causes of diarrhea in kittens

Kitten diarrhea is usually caused by different infectious agents, non-infectious irritants, changes in diets, or a sensitivity/allergic reaction. 

We can divide the most common causes of kitten diarrhea into 4 main groups:

  • Diet – eating something she shouldn’t have, abrupt diet change, food allergy or intolerance
  • Infectious agents – bacteria, parasites, viruses
  • Non-infectious agents – poisonous plants, chemicals… 
  • Stress-related diarrhea

(There are a few other things that can cause kitten diarrhea, but those are not that common and usually need proper diagnostics)

1. Diet

Diarrhea in dogs is often caused by something they ate. Cats, on the other hand, are picky eaters, so this doesn’t happen as often.

However, there is one thing that often causes diarrhea in kittens, and that we see a lot in the veterinary practice – cow’s milk.

It’s a common misconception that milk is good for cats. Cow’s milk (or any other milk) is something cats love but most of them can’t digest it properly. Adult cats are often lactose intolerant since they no longer have the enzyme that handles lactose. So giving your cat milk might result in profuse diarrhea.

I know, I know…” but our neighbor’s cat has no problem with it”. Yes, some cats can tolerate milk. But let me ask you, if you know that you risk making your cat sick (and your home very smelly), are you willing to try it? 🤷‍♀️

There are other things your kitten will enjoy as much that are safe for her. Just ask for special cat treats in your nearest pet store. Or buy a kitten milk replacer that can be mixed with kibbles to help your cat transition to a solid diet.

There are other foods that are toxic to your cat you should be aware of.

Sometimes kittens get diarrhea after an abrupt diet change. When you bring your new kitty home, ask the breeder what she is used to eating and try to change her diet slowly (over 7 days is ideal) to help her digestive tract get used to her new food.

Sometimes the immune system overreacts to a specific food protein, resulting in food intolerance or allergy. If you suspect your cat has a food allergy (or intolerance), talk to your vet about proper diagnostic tests. The gold standard is an elimination diet.

However, in medicine, like in life, things can change. What wasn’t a problem before can suddenly become one and what was a known allergy source can be suddenly tolerated.

If your cat has an allergy or food intolerance, she needs to be monitored and her diet adjusted accordingly.

Kitten diarrhea cow's milk

2. Parasites and bacterial or viral infections

Intestinal parasites like roundworms or tapeworms are often the cause of kitten diarrhea.

If you found your new kitten on the street, the first thing you should do is take her to a vet. Most stray cats have parasites (and some other health problems) that need to be addressed.

❗️Parasites pose a health hazard not just for your cat, but also for you and your other family members. Parasite infection is a zoonosis – a disease that can be transmitted to humans. You should be especially careful if you have small kids.

Your kitten needs to be dewormed at 2 weeks of age since cats can be already born with parasites. Then at 2 weeks intervals until they are 12 weeks old.

Talk to your vet about the proper deworming schema for your darling.

If you purchased your cat from a respectable breeder (or shelter), he can usually show you proof that the kitty was dewormed regularly.

Protozoa (microscopic parasites) like Coccidia, Giardia, Cryptosporidium, or Tritrichomonas can also cause severe kitten diarrhea.

→ The immune system of young animals is more delicate which is making them more susceptible to various bacterial infections. E.coli, Salmonella, Campylobacter, and other bacteria can cause more serious illness, often accompanied by other symptoms such as fever, vomiting, apathy…

Infections with E.coli, Salmonella, or Campylobacter are especially dangerous since they can also be transferred to humans.

→ Perhaps the most dangerous causes of diarrhea in kittens are viral infections, which is why they often require medical attention.

Several viruses can cause kitten diarrhea – feline immunodeficiency virus, feline panleukopenia virus, rotavirus, and feline leukemia virus… Some of them are even life-threatening.

The best way how to protect your can is through vaccination. Talk to your vet about the best vaccination schema for your cat.

Cat planner and cat care printables

3. Non-infectious agents

I love plants, but so did my previous cat. I couldn’t have anything green at home. Even if it wasn’t toxic for him, he ate it or played with it until only stems were left. He loved cat grass but was able to completely mown down a whole pot in less than 10 minutes if left on his own (and then proceeded to vomit it on my living room floor). Sometimes I considered buying a cactus just to see what he would do but I was too afraid I’d end up with an angry cat with thorns in his muzzle 😃

If you want to have plants, talk to your vet about which are ok to have around cats (sadly, there are not that many). I’m not going to make a list, since it strongly depends on where you live.

Also, be sure to store your cleaning supplies and other chemical agents safely.

Kitten diarrhea from plants

4. Stress-related kitten diarrhea

Sometimes stress can cause diarrhea.

Things like changing homes, leaving their mother, or the arrival of a new baby can cause stress-related diarrhea in kittens.

Be sure to give them enough quiet time and space to help them adjust.

How is the cause of kitten diarrhea diagnosed?

Since diarrhea is a symptom that can mean many different things, we look at your cat’s medical history, clinical signs, results of blood and stool tests, and predisposing factors.

Sometimes further diagnostic tools like X-rays or ultrasound are needed.

When you take your cat to a vet, it’s good to know when the problem started, and what else is/was happening (any other signs, behavior changes, changes at home…).

It’s also good to note the frequency, color, consistency, and anything else that might help you describe it to your vet in case you need to. And yes, we vets do find those gross photos really helpful 😛

In case of kitten diarrhea, we will also need a stool sample.

cat planner

When to call a vet if your kitten has diarrhea

If your kitty is playing, drinking enough water, seems generally happy and diarrhea doesn’t last more than 1-2 days, you should be fine.

However, since diarrhea is such a broad general symptom, I would recommend calling your vet and letting him decide.

If your pet displays any of the following symptoms, go see a vet as soon as possible:

  • fever
  • lack of appetite
  • any changes in behavior 
  • bloody diarrhea
  • black stool
  • stool with white flecks in it
  • green stool
  • pale gums
  • apathy (doesn’t want to play, just wants to sleep or lay down…)
  • vomiting
  • discomfort or pain
  • if your pet isn’t drinking water
  • if your pet isn’t vaccinated or hasn’t received all her vaccinations
  • if your pet isn’t dewormed
  • if you think your pet might have swallowed a foreign body
  • if you think your pet might have swallowed toxic substances (toxic plants, rat poison…)
  • if diarrhea has been going on for more than 1-2 days

Cats are very good at masking pain, so any behavior change can be a sign of pain or discomfort.
Call your vet even when something just seems “off”, trust your instincts, from my experience, owners’ instincts when it comes to their cats are usually right 🙂

Treatment of kitten diarrhea

Since it’s a symptom, treatment depends on the cause.

Treatment will vary depending on the cause from supportive treatment, probiotics, deworming products, antibiotics, and medications to surgery or hospitalization.

There are several veterinary diets for cats and kittens with gastrointestinal problems (for example Hill’s prescription diets or Royal Canin veterinary diets). Your vet will advise you which diet is best for your cat’s needs.

Fresh and clean water is very important. Just like babies, kittens are prone to dehydration. Dehydration can lead to collapse and can be potentially life-threatening. So make sure your baby is drinking enough. If not contact your vet.

Please don’t buy any products by yourself, consult with your veterinarian about what’s best for your cat.

How to prevent kitten diarrhea

In many cases, diarrhea can be prevented.

Here are a few tips:

  • vaccinate your cat at appropriate ages 
  • have proper parasite management and prevention plan right from the start
  • if you have house plants – google if they are not poisonous
  • transition your kitten to a new diet slowly (over at least 5 days)

Kittens and other babies have a sensitive gastrointestinal tract and immature immune system, which often leads to diarrhea or other bowel problems.

Kitten diarrhea prevention

Cats are very good at masking pain signs. However, one of the signs that your cat is in pain is pooping and/or urinating outside her litter box.

In general, observing your kitten’s bowel movements is one of the best ways you can monitor your pet’s health.

When you get a new kitty, take her to a vet for a thorough checkup, deworming, and vaccinations. This is the best way you can prevent potentially dangerous health issues.

There are even several pathogens that you or your kids can catch from your cat if you are not careful.

The best thing you can do for your cat (and for you) is to pay attention to her health and follow a preventive care plan with regular deworming, vaccinations, and checkups. And talk to your vet if anything seems “off”!

Enjoy your new family member! ☺️ ❤️

If you want to learn more about pet health, you can sign up for my newsletter. Now you can get a free pet care planner as a bonus 🙂


Marks SL, Willard MD. Diarrhea in Kittens. Consultations in Feline Internal Medicine. 2006:133–43. doi: 10.1016/B0-72-160423-4/50018-4. Epub 2009 May 15. PMCID: PMC7149963.


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