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Cat Diarrhea: Causes & Care Guide (Vet Answer)

If your cat has diarrhea, should you always see a vet? What if your cat has diarrhea but seems fine? Let's look at why cat diarrhea happens and what to do.

Written by: Dr. Eric Barchas (Veterinarian)

Last Updated on July 12, 2024 by Catster Editorial Team

A small gray and white fluffy cat getting out of a litter box.

Cat Diarrhea: Causes & Care Guide (Vet Answer)

One of the Catster editors recently asked me a few questions about poop. She wondered whether she needed to be concerned if her cat had a single runny poop. She also wondered whether pooping outside of the litter box might be a sign of a veterinary problem. Poop doesn’t exactly make the world go ’round, but it is something that, for better or for worse, is a major part of life. So, let’s talk about cat poop and cat diarrhea!

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Cat diarrhea vs. normal cat poop

Ideally your cat produces nicely formed stools without difficulty on a daily basis. They are mostly easy to scoop out of the box, and they’re comparatively innocuous in general.

Cat diarrhea comes in varying levels of severity. Abnormally soft stools can range from incompletely formed to “soft serve” to “cow patty” to liquid to hemorrhagic. Cat diarrhea, like human diarrhea, occurs when residual undigestible portions of food pass through the intestines abnormally fast, or when excess fluid is added to the stool by the large intestines.

Cat Poop Chart
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What causes cat diarrhea?

Practically speaking, there are a number of causes of cat diarrhea. Sometimes, cat diarrhea may be a relatively minor problem such as a mild reaction to a diet change. Mild dietary indiscretion can also cause cat diarrhea. As a child I owned a cat who was lactose-intolerant; on the few occasions I tried to create a Norman Rockwell-esque scene by offering her a saucer of milk (you should never give cow’s milk to a cat!), she created a very non-Rockwell-esque scene in the litter box.

Stress is another potential cause (cat diarrhea can occur if something literally scares the you-know-what out of them). And finally, more serious problems can cause cat diarrhea. These range from treatable issues like parasites and mild intestinal infections to more serious problems such as exposure to toxins, foreign objects in the intestines, liver or kidney disease, inflammatory bowel disease (also known as infiltrative bowel disease, or simply IBD), and cancers such as lymphoma or intestinal adenocarcinoma.

When should you worry about cat diarrhea? What if your cat has diarrhea and seems fine otherwise?

So when is cat diarrhea a big deal? When it’s really bad, when it’s accompanied by other symptoms, or when the cat feels or looks significantly sick.

For instance, if your cat has one soft stool but is still playful and eating and drinking normally, you probably don’t need to rush to the vet. This is especially true if you just switched foods (in which case you should consider switching back), or if you know she consumed a suspicious but not especially dangerous food item (such as turkey skin or milk).

However, if your cat is lethargic, won’t eat, is suffering from profuse hemorrhagic diarrhea, has 10 episodes of diarrhea in one day, or if vomiting occurs concurrently with the diarrhea, then you need to seek veterinary attention. Vomiting and diarrhea often occur together, and they are a dangerous combination because they can trigger severe dehydration.

If your cat is having frequent diarrhea, a checkup is a good idea even if she’s not showing any other symptoms. Some cat parasites can spread to people, and IBD and lymphoma are serious problems. Chronic cat diarrhea should not be ignored.

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Cat diarrhea, cat constipation and pooping outside of the litter box

How about pooping outside of the litter box? Cat diarrhea is a common cause of this behavior, so if your cat has an abnormally soft stool outside of the box, then what you really need to focus on is the diarrhea.

Conversely, constipation also can cause cats to defecate in inappropriate places. This appears to occur because cats grow weary of going back and forth to the litter box without success, and begin trying to eliminate the contents of their bowels wherever they may be. Constipated cats may posture and strain unproductively in or out of the box, and if they produce stool it may be hard and dry.

Constipation isn’t just miserable. It’s also potentially life-threatening, and I have encountered several unfortunate cats who died from the stress of trying to defecate while hopelessly constipated. Cats with urinary obstructions can also sometimes look constipated or pass feces outside of the box while they are straining to urinate, and urinary obstruction is urgently life-threatening. Some cats with masses or tumors in their rectums or near their anuses will defecate outside of the box — often with signs of discomfort.

The bottom line on what to do about cat diarrhea

In short, if your cat seems to be having any distress in passing urine or feces, then book an immediate vet visit.

However, some cats intermittently (or regularly) pass normal bowel movements outside of the litter box. Most of the time this is a behavioral issue. The first step in such cases is to see the vet to be sure there is no medical problem. After getting a clean bill of health, the next step is to implement a behavioral modification plan (this link addresses urinating outside of the box, but the treatment tactics are the same). And take comfort from one fact: Finding cat poop outside of the box may be unpleasant, but it’s better than finding urine.

Thumbnail: Photography by Africa Studio / Shutterstock. 

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