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Why Does My Cat’s Poop Smell So Bad? 8 Vet Approved Reasons & Solutions

Smelly cat poop
Image Credit: catinsyrup, Shutterstock
Last Updated on December 5, 2023 by Catster Editorial Team

Vet approved

	Dr. Paola Cuevas Photo

Reviewed & Fact-Checked By

Dr. Paola Cuevas

MVZ (Veterinarian)

The information is current and up-to-date in accordance with the latest veterinarian research.

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As much as we all love our cats, cleaning out their litter trays is unlikely to top any cat lover’s list of favorite tasks. If your cat’s poop happens to start smelling worse than usual, this can make this job even worse!

Bad-smelling poop can be a sign that something’s wrong with your cat, so it’s important to get to the bottom of the problem, so to speak! We’ve collected the top six reasons that your cat’s poop might be smelling so bad and more importantly, what you can do about it.

First, though, if your cat’s stinky poop hasn’t freshened up after a couple of days, seek veterinary advice. If their bad-smelling poop is accompanied by vomiting or blood or has a diarrhea consistency, seek an emergency veterinarian.

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The 8 Reasons Your Cat’s Poop Smells So Bad

1. Diet

Introducing a new food to your cat’s diet can sometimes lead to smelly poop, often with a loose consistency. If you plan to change your cat’s diet without a specific medical reason for it, you should always try to do it gradually. You can change to the new diet over a period of 10 days by adding 10% of the new diet every day. This will allow your cat’s digestive system to adapt to the new diet.

Your cat might have eaten something that disagreed with them, like a mouse or something else that they managed to catch. Cats are carnivores, but protein-rich foods can also cause smelly poop. Cats can develop intolerances to grains or sensitivity to any of the ingredients in a formula, both of which can cause smelly poop as a result.


 Talk to your vet about changing your cat’s diet or eliminating certain ingredients to see if these may be the trigger for your cat. This problem will resolve by itself if your cat’s digestive system is not sensitive to any of the ingredients in the new diet. If the stinky poop problem continues for more than 48 hours after a dietary change, let your veterinarian know about this.

cat food in feeding bowl
Image Credit: Africa Studio, Shutterstock

2. Bacteria

If your cat eats something that’s been contaminated with bacteria like E. coli or Salmonella spp., this may cause smelly poop, as well as indigestion, inflammation, and diarrhea. Some cats love to hunt for food (even if they don’t need to!), and eating rodents or birds can put them at risk of a bacterial infection.

  • Solution: If your cat’s smelly poop doesn’t return to normal after 48 hours, seek vet advice.

3. Parasites

Certain types of intestinal parasites can cause excessive gas, diarrhea, and stinky poop. Giardia, coccidia, and trichomonas infestations can all result in your cat’s intestines becoming inflamed, too.


 Your vet may want to test your cat for parasites, and they will recommend an anti-parasite or worming program depending on the level and type of infestation.

4. Digestive issues

If your cat’s digestive system is unable to digest or absorb fats and starches within their diet, this can result in particularly stinky poop. The technical terms for these digestive issues are maldigestion and malabsorption. Cats can also suffer from specific food sensitivities and intolerances. All of these digestive issues can result in bloating, gas, and stinky poop.


Your vet will need to run tests to determine if your cat is suffering from maldigestion or malabsorption, sensitivities or any other digestive issue and they will advise you on how to treat each one accordingly.

A man hand strokes a cat on a sore stomach
Image Credit: Zhuravlev Andrey, Shutterstock

5. Medications

Certain medications, including hormonal medication and pain relievers, can cause smelly poop. Some vitamin and mineral supplements can also cause stinky poop.


Speak to your vet to rule out the possibility of medications causing foul-smelling feces. Most cat foods these days are completely balanced when it comes to vitamins and minerals, so never add a supplement to your cat’s diet without speaking to your vet first.

6. Anal gland infection

If your cat’s anal glands become infected, they might not drain properly. This can result in a foul-smelling discharge that can end up covering their poop and elsewhere!


If you notice a foul smell that doesn’t just seem to be confined to the litter box, ask your vet to check your cat’s anal glands. Your cat may need their anal glands to be manually expressed or drained or medication to clear up an infection.

7. Cat litter

Natural cat litters like paper, unscented clay, and wood pellets often hold onto the smell of cat poop, even after you’ve cleaned the tray. Your cat’s poop might not smell any worse than normal, but that lingering smell can soon become unpleasant.


Switch to a scented cat litter or one with odor control such as baking soda. If you continue using unscented litter, it can help to clean them out as often as possible, as well as doing a full litter change once or twice a week.

Even the best cat litter can quickly start smelling bad. To avoid the expense and inconvenience of constantly replacing your litter, you can try a great litter additive like Hepper's Advanced Bio-Enzyme Cat Litter Deodorizer, a natural product that uses bio-enzymes to neutralize odors.

hepper bio enzymatic litter additive

This deodorizer works on all types of litter and won't disrupt your cat's litter box habits.

At Catster, we’ve admired Hepper for many years and decided to take a controlling ownership interest so that we could benefit from the outstanding designs of this cool cat company!

Image Credit By: Axel Bueckert, Shutterstock

8. Not covering up their poop or pooping outside the litter tray

Even if your cat’s poop isn’t any smellier than usual, if they’re not covering it up in the litter tray, then it’s going to start to smell bad. This may be a sign that the litter is hurting your cat’s paws, or they don’t like the texture or smell of the litter. Cats pooping outside the litter tray may be having trouble accessing a tray with high sides, or the tray is too small.


Try switching to a different brand of litter or offering your cat a tray with lowered sides or one that’s much larger. Ask your vet to check that your cat isn’t in pain. Cats who are stressed about a recent change in circumstances may also poop outside their litter tray.

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Wrapping it up

If your cat’s smelly poop is also diarrhea-like in consistency, it’s doubly important to get them checked by a vet as soon as possible. Ongoing or recurrent diarrhea can be the result of an underlying condition, like kidney disease, liver disease, or a hyperactive thyroid. Your vet will need to run tests to determine the exact cause.

If smelly poop is combined with lethargy, lack of appetite, or vomiting, call your vet as a matter of urgency.

Always keep your cat’s litter tray as clean as possible, and monitor your cat’s poop so you can quickly tell if something is wrong. You may smell it before you see it, and that’s always a sign that something isn’t quite right!

If your cat’s stinky poop is combined with other issues, like pooping outside the litter box, your cat may be suffering from an underlying health condition. Speaking to your vet as soon as possible is the best course of action.

Certain stinky poop problems can easily be solved by changing the type of litter that you use or adjusting your cat’s diet. Others may need medication and ongoing treatment. Whatever the issue, seeking advice from your vet is essential, and then you can start looking forward to a happier cat and a pleasant-smelling home once again!

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Featured Image: catinsyrup, Shutterstock

About the Author

Emma Stenhouse
Emma Stenhouse
Emma is a freelance writer, specializing in writing about pets, outdoor pursuits, and the environment. Originally from the UK, she has lived in Costa Rica and New Zealand before moving to a smallholding in Spain with her husband, their 4-year-old daughter, and their dogs, cats, horses, and poultry. When she's not writing, Emma can be found taking her dogs for walks in the rolling fields around their home...and usually, at least some of the cats come along, too! Emma is passionate about rescuing animals and providing them with a new life after being abandoned or abused. As well as their own four rescue dogs, she also fosters dogs for re-homing, providing them with love and training while searching for their forever homes.

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