Soft Stool & Diarrhea in Cats: Causes & When to Worry

Let's talk about poop.

Because if you own a cat, you've probably spent more time looking at a litter box than you ever expected to in your life. And once you start paying attention to it, it's very easy to become convinced that every slightly soft stool means something is terribly wrong.

Sometimes it does mean something is going on. Sometimes your cat ate something weird. Sometimes you changed their food. Sometimes they had a stressful day. And sometimes... they just had one weird poop.

So before you panic, let's talk about some of the more common reasons a cat might have soft stool or diarrhea, what you can reasonably watch at home, and when it's time to stop troubleshooting and call your veterinarian.

A quick disclaimer: This is general educational information based on my experience with cats and kittens, not veterinary advice or a diagnosis. I am not your cat's veterinarian, and a blog post can't tell you why an individual cat has diarrhea. If your cat is sick, you're concerned about their condition, or symptoms are persistent or severe, contact your veterinarian. When in doubt, I'd rather you call than assume everything is fine because something you read online made you feel better.

Not Every Soft Stool Is a Big Deal

First, there's a pretty big difference between one stool that's a little softer than usual and a cat who has repeated watery diarrhea.

A healthy adult cat who has one soft bowel movement after a stressful day is a very different situation from a kitten who has had diarrhea several times, isn't eating, and is acting lethargic.

That's why I don't think it's particularly helpful to look at one litter-box deposit in isolation. I pay attention to the stool, but I also pay attention to the cat.

Are they eating normally? Are they acting like themselves? Are they drinking? Are they playful and alert? Are they maintaining their weight? Is this a one-time thing, or is it happening over and over?

Those questions give you a lot more useful information than whether one particular poop was perfectly formed.

Food Changes Can Cause Soft Stool

One of the most common explanations for a sudden change in stool is also one of the least exciting: you changed the food.

A cat's digestive system has to adjust when you change what they're eating, and a sudden food change can cause temporary diarrhea or softer stools. Some cats barely notice a change in diet, while others apparently require several days of consideration before approving a new menu.

This is one reason I generally prefer gradual transitions when possible.

That doesn't mean every cat needs a two-week transition. Some cats can switch foods with almost no reaction at all. Others are much more sensitive, especially if you're changing the protein, texture, brand, or type of food.

So if your cat develops a little soft stool shortly after a food change but is otherwise completely normal, I wouldn't automatically assume you've discovered a serious food intolerance or that the new food is "bad." Sometimes the digestive system simply needs a little time to adjust.

If you're in the middle of changing foods, see [How to Transition Your Cat to a New Food] for more on how I approach that.

Stress Can Affect Digestion Too

Cats are creatures of habit, and they don't always handle changes in their environment as casually as we might expect.

Moving to a new home, traveling, going to the veterinarian, bringing home another animal, having visitors, changing their routine, or simply experiencing something stressful can affect a cat's digestion.

This is especially worth remembering with kittens.

Imagine being taken away from your mother and littermates, driven somewhere you've never been, brought into a completely unfamiliar house, surrounded by strange smells and sounds, and then expected to eat dinner like nothing happened.

I would probably have some digestive opinions too.

That's one reason I don't want people to see a slightly soft stool during the first few days after bringing home a kitten and immediately assume something is terribly wrong. A new environment is a huge transition, and stress alone can sometimes affect the litter box.

That doesn't mean persistent diarrhea should be ignored. It just means that context matters.

Sometimes It's Just a Weird Poop

This is probably the part that gets lost when people start researching cat digestion online.

One day of weird poop does not necessarily mean your cat has a problem.

Cats aren't machines. Their stool can vary a little from day to day depending on what they ate, how much they ate, stress, activity, and things you may never identify.

If your cat has one softer-than-usual stool and then goes right back to normal, is eating normally, acting normally, and otherwise seems completely fine, I wouldn't immediately start changing their entire diet, adding six supplements, buying probiotics, and scheduling every test available.

Sometimes you just watch them and see what happens.

That isn't the same thing as ignoring a problem. It's recognizing that one imperfect bowel movement isn't necessarily a problem that needs to be solved.

What About Parasites?

Parasites are another possibility, particularly when digestive problems persist or keep coming back.

And this is one of those things where even a very conscientious cat owner can't simply look at a cat and know what's going on. There are several gastrointestinal parasites that can cause diarrhea, including worms and protozoal infections such as Giardia and coccidia.

Obviously, prevention matters. At RBC, we take parasite prevention seriously and routinely deworm our kittens, so it's not something I expect to be the explanation for soft stool in one of my kittens.

But no prevention program makes a cat completely incapable of ever being exposed to a parasite, and some parasites aren't addressed by every deworming medication.

So if a cat has persistent or recurring diarrhea, a fecal examination may be much more useful than continuing to change foods and hoping something sticks.

Sometimes you need to find out what you're actually dealing with.

What If the Cat Eats Raw?

If your cat eats raw, it can be tempting to blame raw food every time the stool changes. I don't think that's particularly helpful and it shouldn't cause changes to stool more than any other diet.

Raw-fed cats can have digestive upset for all the same reasons other cats can. They can experience stress, food changes, parasites, illness, eat something they shouldn't, or simply have an occasional strange bowel movement. At the same time, raw food is still food, and individual cats can absolutely respond differently to particular foods, proteins, fat levels, or changes in diet.

So if your raw-fed cat develops soft stool, I'd look at the whole situation. Did you just introduce a new protein? Did you change brands? Did you increase the amount of food? Did they get into something? Did something stressful happen? Is this the first occurrence, or has it been happening repeatedly?

And, most importantly, how does the cat feel?

If you're feeding raw, food safety matters too. Raw food should be stored and handled appropriately, and persistent digestive symptoms shouldn't automatically be dismissed as just "part of eating raw."

I cover the food-safety side in [Salmonella & Raw Feeding].

Don't Change Five Things at Once

This is probably one of the easiest ways to make a simple digestive problem much harder to figure out.

The cat has soft stool, so you change the food, add probiotics, add pumpkin, change proteins, stop treats, start a new supplement, and change feeding times all at once.

And then the poop gets better.

Great!

But what fixed it?

You have absolutely no idea.

Now you've created a pretty good detective mystery for yourself.

If your cat is otherwise doing well and you're dealing with a mild, short-lived issue, I prefer making changes thoughtfully rather than throwing the entire feeding routine into chaos. If the problem is more significant or persistent, though, that's when I'd stop trying to solve it through internet troubleshooting and involve your veterinarian.

What About Blood in the Stool?

This is one that tends to make people panic, and I understand why. Nobody wants to see blood in the litter box.

But blood in the stool doesn't automatically mean your cat is having a life-threatening emergency, either.

A small amount of bright-red blood can sometimes occur when the lower intestinal tract is irritated, including during an episode of diarrhea or inflammation. So if you see a tiny streak of bright-red blood in an otherwise completely normal cat, I wouldn't necessarily assume the worst.

I also wouldn't completely ignore it.

Blood can have many causes, including irritation, parasites, dietary problems, inflammation, infections, and other gastrointestinal conditions. If it happens repeatedly, there is a significant amount of blood, or your cat has other symptoms, that's a much different situation than finding one tiny streak once.

Black or tarry stool is also different from a small amount of bright-red blood. Black, tarry stool can indicate digested blood from higher in the gastrointestinal tract and does warrant veterinary attention.

So my approach is basically: don't freak out, but don't shrug it off either.

Take note of what you saw and how your cat is acting. If the blood continues, you see more than a small amount, or your cat isn't acting normally, contact your veterinarian.

When Should You Call the Vet?

There is a point where "let's see what happens" stops being a good plan.

I'd contact your veterinarian if diarrhea is persistent, keeps coming back, or is accompanied by repeated vomiting, poor appetite, lethargy, weakness, obvious pain, dehydration, weight loss, or other changes in behavior.

I'd also be quicker to call with a very young kitten, an elderly cat, or a cat with an existing medical condition. Those cats have less room for prolonged digestive problems than an otherwise healthy adult cat.

Repeated or significant blood in the stool deserves veterinary attention as well, as does black or tarry stool.

And if you think your cat may have eaten something toxic or swallowed a foreign object, that's not a situation I'd try to troubleshoot with a food change.

You also don't need to prove to yourself that your cat is seriously sick before calling the vet. If something about the situation doesn't seem right to you, that's a perfectly reasonable reason to ask.

What Will the Vet Want to Know?

If you do end up calling or going to the veterinarian, having some basic information can make the conversation much more useful.

Think about when the diarrhea started, how often it's happening, what the stool looks like, whether you've seen blood or mucus, what your cat has eaten recently, whether you changed foods, whether they've had new treats or supplements, and whether anything stressful has happened recently.

It's also helpful to know when your cat was last dewormed and whether they've had any recent changes in weight, appetite, or behavior.

And if your veterinarian asks you to bring in a fecal sample, bring one if you can (as clear of litter debris as possible!). Parasites aren't always visible to the naked eye, so a stool sample can sometimes tell you something you simply couldn't determine by looking at the litter box.

Final Thoughts: Don't Let the Litter Box Run Your Life

I say this lovingly because cat people can get very invested in poop.

Once you start paying attention to it, you can find yourself standing over the litter box thinking, "Was that a 3 or a 3.5?"

Pay attention, absolutely. Changes in stool can be useful information, and sometimes they're the first clue that something is wrong. But you don't need to panic over every imperfect poop.

A temporary change after a stressful event or food transition can happen. A single soft stool in an otherwise completely normal cat isn't necessarily a crisis.

At the same time, persistent diarrhea, recurring digestive problems, significant or repeated blood, black stool, or a cat who isn't feeling well deserves more than a shrug and a new bag of food.

Watch the cat, not just the poop.

Look at the whole picture, pay attention to patterns, and give your veterinarian a call when something doesn't seem right.

That's really the balance I want this article to give you: don't panic over every soft stool, but don't ignore a pattern just because you found a reassuring explanation on the internet.

There is a lot you can learn by paying attention to your cat. You just don't have to diagnose them yourself.