Cat Diarrhea: 7 Common Causes, What to Do, and When to Worry

Cleaning a litter box isn’t anyone’s favorite part of living with a cat, but it does give you one useful advantage: you get regular clues about what’s happening inside your cat’s digestive system.

That’s why suddenly finding loose or watery stool deserves attention.

Cat diarrhea isn’t a disease itself. It’s a symptom.

Sometimes the explanation is relatively simple. Your cat may have eaten something unusual, experienced stress, or reacted to an abrupt food change. Other times, diarrhea can accompany parasites, infections, inflammatory gastrointestinal disease, toxins, or problems elsewhere in the body.

The challenge is figuring out when you can monitor the situation and when your cat needs professional help.

Cornell University’s Feline Health Center guidance on diarrhea explains that diarrhea results when material moves through the intestinal tract too quickly for normal absorption of water and nutrients. Cornell recommends prompt veterinary care when diarrhea persists beyond a day or two and occurs with signs such as poor appetite, lethargy, or vomiting.

Here’s what cat owners should know.

What Does Cat Diarrhea Look Like?

Healthy cat stool is generally formed enough to hold its shape.

Diarrhea can range from stool that’s simply softer than normal to completely watery bowel movements.

You may notice:

• Soft, poorly formed stool
• Watery stool
• Increased bowel movements
• Urgency
• Mucus
• Blood
• Unusual stool color
• Accidents outside the litter box
• Stool stuck around the rear fur

If you have several cats sharing litter boxes, identifying which cat has diarrhea can be surprisingly difficult.

Watch their litter-box habits more closely and consider temporarily providing separate boxes if necessary to determine who’s affected.

The stool matters, but your cat’s overall condition matters even more.

A bright, playful adult cat with one soft bowel movement presents a very different situation from a kitten with repeated watery diarrhea, vomiting, and no interest in food.

1. A Sudden Change in Food

Think back over the last few days.

Did you switch your cat’s food?

Introduce a new flavor?

Offer unfamiliar treats?

Did someone give your cat table scraps?

An abrupt dietary change can temporarily disturb the gastrointestinal tract. Cornell specifically identifies sudden diet changes as one possible reason a cat may experience a brief bout of diarrhea.

This doesn’t automatically mean the new food is bad or that your cat has developed an allergy.

The transition itself may simply have been too abrupt.

When changing your cat’s regular food for non-medical reasons, a gradual transition is generally easier on the digestive system unless your veterinarian has instructed you differently.

If diarrhea keeps returning, however, don’t spend months jumping between foods.

Recurring digestive problems deserve investigation.

2. Your Cat Ate Something They Shouldn’t

Cats may have a reputation for being selective eaters, but they’re also curious.

A cat can get into:

• Spoiled food
• Garbage
• Human food
• Houseplants
• Another pet’s food
• Insects or prey
• Household substances

Sometimes this causes temporary gastrointestinal irritation.

Other exposures are much more serious.

For example, Cornell’s feline poison guidance lists vomiting and diarrhea among possible signs of poisoning and advises prompt veterinary attention when poisoning is suspected.

If you think your cat may have swallowed a toxic plant, human medication, household chemical, antifreeze, pest-control product, or another dangerous substance, don’t wait to see whether the diarrhea stops.

Contact a veterinarian or appropriate animal poison service immediately.

Don’t induce vomiting unless a veterinary professional specifically instructs you to do so.

3. Stress

Cats appreciate predictability more than we sometimes realize.

A seemingly ordinary change in your household can be significant from your cat’s perspective.

Potential stressors include:

• Moving
• Boarding
• Traveling
• A veterinary visit
• A new baby
• A new pet
• Visitors
• Construction
• Changes in feeding routines
• Changes to the litter-box environment

Cornell notes that stressful situations such as travel or a stay at a veterinary clinic can sometimes cause a short episode of loose stool.

If the diarrhea occurs during a stressful event but your cat otherwise seems completely normal, it may settle as their routine returns to normal.

Still, stress shouldn’t become the automatic explanation for persistent diarrhea.

If symptoms continue or your cat becomes unwell, another cause needs to be considered.

4. Intestinal Parasites

Parasites are an important possibility, particularly in kittens and cats with relevant exposure.

Cornell reports that gastrointestinal parasites are common in cats and can produce signs including diarrhea, vomiting, reduced appetite, mucus or blood in stool, poor coat condition, and dehydration.

Examples include:

• Roundworms
• Hookworms
• Coccidia
• Giardia
• Other gastrointestinal parasites

Some are microscopic.

So:

“I checked the litter box and didn’t see worms”

doesn’t rule out parasites.

Giardia, for example, is a microscopic protozoan parasite rather than something you’re likely to identify by casually looking at stool.

Kittens deserve particular attention. Cornell notes that coccidia can cause significant disease and mucous diarrhea in kittens even though infection may cause few problems in healthy adult cats.

Veterinarians may request a fresh stool sample to test for parasites and other potential causes.

5. Infection

Bacterial and viral infections can also cause cat diarrhea.

One serious example is feline panleukopenia, particularly in susceptible or inadequately vaccinated cats.

But diarrhea alone can’t tell you which infection—if any—is responsible.

That’s why looking at accompanying symptoms is important.

Be more concerned when diarrhea occurs alongside:

• Fever
• Vomiting
• Severe lethargy
• Loss of appetite
• Weakness
• Dehydration
• Rapid deterioration

Don’t try to identify an infectious disease from photographs of stool online.

Different gastrointestinal conditions can produce very similar-looking diarrhea.

A veterinarian can decide whether testing is appropriate based on your cat’s age, vaccination history, exposure, symptoms, and physical examination.

6. Inflammatory Gastrointestinal Disease

Diarrhea that keeps returning over weeks or months deserves more investigation than a single episode.

One possible explanation is inflammatory bowel disease, often abbreviated as IBD.

Cornell describes feline IBD as a group of chronic gastrointestinal disorders involving inflammatory cells within the digestive tract. Possible signs include diarrhea, vomiting, weight loss, reduced appetite, bloody stool, and lethargy.

But there’s an important warning here:

Chronic diarrhea does not automatically mean IBD.

Many diseases produce similar symptoms.

Cornell notes that diagnosing IBD requires an extensive workup because its clinical signs overlap with other conditions.

So don’t diagnose your cat based on an internet checklist.

If diarrhea is recurring, keep track of how frequently it happens and discuss the pattern with your veterinarian.

7. A Medical Problem Outside the Intestines

Sometimes diarrhea is part of a bigger medical picture.

The digestive system doesn’t operate independently from the rest of the body.

Cornell notes that prolonged or recurring feline diarrhea can accompany problems outside the intestinal tract, including diseases involving the thyroid, kidneys, or liver, as well as other systemic conditions.

Hyperthyroidism is one example particularly relevant to older cats. Cornell’s internal-medicine guidance notes that an overactive thyroid can produce weight loss and behavioral changes along with vomiting and diarrhea.

This is why context matters so much.

Suppose your senior cat develops occasional diarrhea but is also:

• Losing weight
• Drinking more
• Urinating more
• Eating unusually large amounts
• Acting differently

Those additional changes are valuable information for your veterinarian.

Don’t treat each symptom as though it exists in isolation.

What If Your Cat Has Diarrhea and Vomiting?

Diarrhea combined with vomiting deserves closer attention because your cat is losing fluid through two routes.

Our guide to cat vomiting and when to worry explains the wide range of reasons cats may vomit, from relatively minor problems to foreign objects, toxins, and underlying disease.

When vomiting and diarrhea occur together, monitor your cat’s:

• Energy
• Appetite
• Drinking
• Urination
• Gum moisture
• General behavior

Cornell identifies vomiting and diarrhea among conditions that can contribute to dehydration in cats.

Repeated vomiting plus watery diarrhea is much more concerning than one slightly soft bowel movement.

Can You Treat Mild Cat Diarrhea at Home?

This depends on your cat.

An otherwise healthy adult cat with a single mild episode and completely normal behavior may simply need close observation.

But kittens, elderly cats, cats with chronic medical conditions, and cats showing other symptoms deserve a lower threshold for veterinary advice.

Keep Water Available

Fresh water should remain easily accessible.

Diarrhea causes the body to lose fluid, and prolonged diarrhea can lead to dehydration and electrolyte problems. The Merck Veterinary Manual warns that continuing diarrhea can cause dehydration and electrolyte imbalance when substantial amounts of fluid are lost.

Make water easy to reach.

Cats that eat wet food also receive part of their daily water intake through food.

If your cat isn’t drinking, cannot keep water down, or appears dehydrated, contact your veterinarian.

Don’t Keep Changing Foods

It’s tempting to try three different foods in two days.

Don’t.

That can make the digestive system—and your attempt to identify the trigger—even more confused.

If you recently changed diets and diarrhea started shortly afterward, contact your veterinarian for guidance on how to proceed.

Keep the Litter Box Clean

Clean litter boxes make monitoring much easier.

You’ll be better able to track:

• Frequency
• Consistency
• Blood
• Mucus
• Urination
• Improvement or worsening

This is particularly valuable in multi-cat households.

Should You Give a Cat Human Anti-Diarrhea Medicine?

Not without veterinary guidance.

Human medications aren’t automatically safe for cats.

Cornell specifically warns that some over-the-counter medications can be harmful to cats with diarrhea.

Don’t give your cat:

• Human anti-diarrheal medication
• Leftover antibiotics
• Another pet’s medication
• Random supplements
• Herbal mixtures

just because someone online says they worked for their pet.

The correct treatment depends on the cause.

Parasites, inflammatory disease, toxicity, dietary upset, and infection aren’t interchangeable problems.

What Does Blood in Cat Diarrhea Mean?

Blood deserves attention.

You might see bright red streaks or darker stool.

Bright red blood can originate from lower portions of the gastrointestinal tract, while black, tarry stool may suggest digested blood from higher in the digestive system.

Merck notes that black, tarry feces can indicate bleeding in the stomach or small intestine.

Don’t try to determine the seriousness entirely from color.

If there’s substantial blood, black tarry stool, or your cat appears ill, contact a veterinarian promptly.

A photograph can be useful.

When Should You Call a Veterinarian?

Contact your veterinarian when diarrhea:

• Persists beyond a day or two
• Happens repeatedly
• Becomes severe or very watery
• Contains substantial blood
• Appears black and tarry
• Occurs with repeated vomiting
• Is accompanied by lethargy
• Occurs with poor appetite
• Is associated with weight loss
• Appears to cause pain
• Occurs after suspected toxin exposure

Cornell specifically recommends seeking veterinary care promptly when diarrhea continues for more than a day or two and is accompanied by systemic signs such as poor appetite, lethargy, or vomiting.

You should seek help sooner if your cat appears seriously unwell.

Why Kitten Diarrhea Deserves Extra Attention

Kittens are small.

That means fluid loss can become important more quickly, and they’re also vulnerable to certain infectious and parasitic diseases.

Don’t assume a kitten simply has a “sensitive stomach.”

Diarrhea in a kitten accompanied by vomiting, reduced appetite, lethargy, weakness, or poor growth warrants veterinary attention.

Parasite testing is particularly relevant because Cornell notes that gastrointestinal parasites can cause more significant disease in kittens.

Keep young cats on an appropriate veterinary preventive-care schedule.

What Will Your Veterinarian Want to Know?

The more useful information you provide, the better.

Be ready to answer:

When did it begin?

How often is your cat passing stool?

What does it look like?

Is there mucus or blood?

Is your cat vomiting?

Are they eating?

Has their food changed?

Could they have eaten something unusual?

Are other cats affected?

Has your cat lost weight?

Have drinking or urination habits changed?

A fresh stool sample may also be useful.

Cornell’s diagnostic laboratory includes fecal testing for parasites and infectious organisms among the tools available when investigating feline diarrhea.

Depending on the situation, your veterinarian may recommend additional bloodwork or imaging.

Can You Prevent Cat Diarrhea?

Not every episode is preventable, but good everyday habits reduce avoidable problems.

Make dietary changes gradually.

Keep toxic substances and dangerous plants inaccessible.

Follow your veterinarian’s parasite-prevention recommendations.

Maintain clean food and water dishes.

Keep litter boxes hygienic.

Schedule appropriate veterinary preventive care.

And pay attention to changes in appetite, weight, drinking, stool, and behavior.

Your cat can’t tell you:

“My stomach hasn’t felt right for three weeks.”

Their habits often tell the story instead.

Frequently Asked Questions

Why does my indoor cat have diarrhea?

Indoor cats can still experience dietary upset, stress, parasites, infections, inflammatory gastrointestinal disease, food-related problems, and systemic illnesses. Indoor living doesn’t eliminate every possible cause.

Can changing cat food cause diarrhea?

Yes. An abrupt diet change can temporarily upset a cat’s digestive system. If diarrhea persists or other symptoms appear, contact your veterinarian.

Can stress cause diarrhea in cats?

It can. Travel, boarding, household changes, and other stressful events may cause temporary loose stool in some cats. Persistent diarrhea shouldn’t automatically be attributed to stress.

Why does my cat have diarrhea but seem fine?

Some mild episodes occur while a cat otherwise behaves normally. Monitor closely, but seek veterinary advice if the diarrhea persists, becomes severe, or other symptoms develop.

Can worms cause diarrhea in cats?

Yes. Several gastrointestinal parasites can cause diarrhea, and some can’t be seen with the naked eye. Veterinary fecal testing may be necessary.

Final Thoughts

Cat diarrhea isn’t something to panic about every time you find one soft stool in the litter box.

But it shouldn’t automatically be ignored either.

Look at the whole cat.

A healthy adult with one loose bowel movement and normal appetite, energy, drinking, and behavior may simply need monitoring.

A kitten with repeated diarrhea and vomiting needs a much more cautious response.

Likewise, a senior cat losing weight while experiencing recurring diarrhea deserves investigation even if the symptoms don’t look dramatic.

Diet changes, stress, parasites, infections, inflammatory disease, toxins, and systemic medical conditions can all produce diarrhea.

That’s why the best question isn’t simply:

“How do I stop my cat’s diarrhea?”

It’s:

“Why is my cat having diarrhea?”

Once you understand the cause, you and your veterinarian can make much better decisions about what your cat actually needs.

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