Cat Diarrhea: Causes, Symptoms & Solutions

Loose stool in a cat can be worrying, especially when it appears suddenly or your cat seems uncomfortable. Some episodes are mild and pass quickly. Others point to parasites, infection, food sensitivity, inflammatory bowel disease, organ disease, or another condition that needs veterinary care.

In this guide, we’ll walk through what diarrhea is, common diarrhea causes in cats, when it’s safe to monitor at home, and when it’s time to call your veterinarian.

What Is Diarrhea in Cats?

Diarrhea means stools that are softer than normal, loose, or completely watery, often passed more frequently or urgently than usual. It’s a symptom, not a disease by itself.

Cat diarrhea can be:

• Mild and short-term (for example, after a small diet upset), or
• A sign of a more serious problem, like infection, parasites, inflammatory bowel disease (IBD), or organ disease.

How to Tell If It’s Really Diarrhea

Look at both texture and pattern.

• Stool consistency:
  • Normal: formed, log-shaped stool that can be lifted from the litter box easily
  • Soft: still has some shape, but looks moist or squishy
  • Diarrhea: loose, pudding-like, watery, or spread through the litter
• Bathroom pattern:
  • Normal: many adult cats pass stool once or twice daily
  • Possible diarrhea: repeated litter box trips, small amounts passed several times, sudden urgency, or accidents outside the box

If your cat’s stool becomes watery, much more frequent, or clearly different from their usual pattern, treat it as diarrhea.

Acute vs. Chronic Diarrhea

• Acute diarrhea starts suddenly and lasts a few days or less. Often linked to diet changes, stress, or a minor infection. Many cases are mild but can still become serious if your cat is very young, old, or has other illnesses.
• Chronic diarrhea lasts for several weeks or longer or recurs frequently. This is more likely related to long-term issues such as IBD, food allergies, parasites, or other medical conditions.

Duration matters: the longer the diarrhea goes on, the higher the risk of dehydration and weight loss, and the more important a full veterinary work-up becomes.

Common Causes of Diarrhea in Cats

What causes cat diarrhea? The answer is many things. Here are the most frequent categories your vet considers.

Diet-Related Causes

Diet issues are some of the most common causes in cats:

• Sudden food changes: Switching brands or types of food overnight can upset the gut. Vets usually recommend transitioning over 7-10 days.
• Eating spoiled food or garbage: Table scraps, spoiled meat, or raiding the trash can all cause acute diarrhea.
• Food intolerance or sensitivity: Some cats can’t handle certain proteins (e.g., beef, dairy) or rich treats.
• Overfeeding or too many treats: A big, fatty meal can overwhelm the digestive system.

These cases often cause acute, self-limited diarrhea, but if symptoms are strong or last more than a couple of days, a vet visit is still important.

Parasites

Intestinal parasites are a very common cause, especially in kittens and cats from shelters or multi-cat homes.

• Worms: Roundworms, hookworms, and tapeworms can irritate the intestines and cause diarrhea, poor growth, and a dull coat.

Protozoa:

• Giardia may cause soft, greasy, greenish, or mucus-covered stool and can be associated with weight loss.
• Coccidia can cause foul-smelling diarrhea and dehydration, especially in young kittens.

Indoor cats are not completely protected from parasites. Exposure can happen through other pets, contaminated water, potting soil, or tracked-in material. Regular fecal testing and deworming help reduce that risk.

Infections

• Bacterial infections: Infections (e.g., Salmonella, Campylobacter, Clostridium) can cause acute, sometimes bloody diarrhea, especially in young cats or group settings.
• Viral infections: Feline panleukopenia virus and certain coronaviruses can cause severe diarrhea, vomiting, and life-threatening dehydration, particularly in unvaccinated cats.

Infectious causes often need prompt veterinary attention and supportive care.

Stress and Environmental Changes

Cats can react physically to stress. Digestive upset may appear after changes such as:

• Moving to a new home
• A new baby, visitor, or pet
• Boarding or travel
• Loud renovations
• A change in routine
• A litter box being moved

Stress colitis can develop when the large intestine becomes irritated during stressful periods. The stool may contain mucus and, in some cases, a small amount of blood.

Inflammatory Bowel Disease

Inflammatory bowel disease is an ongoing inflammatory condition affecting the gastrointestinal tract. Cats with IBD often have:

• Chronic or intermittent diarrhea
• Weight loss
• Vomiting
• Reduced or sometimes increased appetite

IBD usually needs long-term management with special diets, medications, and regular follow-up with your vet.

Food Allergies

A true food allergy involves an immune reaction to something in the diet. Signs can include:

• Chronic diarrhea and/or vomiting
• Itchy skin or ears
• Sometimes blood or mucus in the stool

Food allergies can look similar to IBD, and the two may overlap. Your veterinarian may recommend a strict elimination diet to narrow down which ingredient is causing trouble.

Toxins and Medications

• Household toxins: Certain plants, chemicals, and human foods can irritate or damage the gut.
• Human medications: Even small doses of ibuprofen, acetaminophen, or other drugs can be dangerous.
• Some prescriptions: Certain antibiotics or anti-inflammatory drugs may cause diarrhea as a side effect.

Always call a professional vet or a pet poison hotline if you suspect your cat ate something toxic.

Other Medical Conditions

Diarrhea is not always caused by the intestines alone. Other health problems can affect stool as well.

• Pancreatitis: An inflamed pancreas can cause abdominal pain, vomiting, reduced appetite, and diarrhea.
• Hyperthyroidism: An overactive thyroid may cause weight loss, increased appetite, and chronic diarrhea, especially in older cats.
• Liver or kidney disease: These affect how the body processes wastes and fluids.
• Cancer: Intestinal lymphoma and other gastrointestinal cancers can cause chronic diarrhea and weight loss, particularly in middle-aged or senior cats. 

What to Look For When Your Cat Has Diarrhea

When you notice cat diarrhea, try to observe and note the following for your vet.

Stool Appearance and Frequency

• Colour: brown is typical. Black, tarry stool can indicate digested blood; bright red streaks suggest fresh bleeding in the colon.
• Consistency: soft, watery, or containing mucus.
• Frequency: Is your cat going more often? Straining? Having accidents?

Other Symptoms That Matter

Take note if your cat also has:

• Vomiting
• Lethargy or weakness
• Not eating or eating much less
• Weight loss over time
• Signs of dehydration: dry, tacky gums, sunken eyes, less urine, or skin that doesn’t snap back quickly when gently lifted.

Duration of Diarrhea

Tell your vet:

• Did the diarrhea start today, a few days ago, or weeks ago?
• Has this happened before?
• Is it getting better, worse, or staying the same?

Acute episodes may resolve quickly, but diarrhea that lasts more than a few days or keeps returning always needs a veterinary exam.

When Is Cat Diarrhea an Emergency?

Call an emergency vet immediately if you see:

• Blood in the stool (bright red or black/tarry)
• Severe lethargy, collapse, or if your cat is too weak to move normally
• Repeated vomiting plus diarrhea
• Signs of pain (crying, hunching, hiding, growling when touched)
• Kittens or senior cats with ongoing diarrhea can become dangerously dehydrated in less than a day.

When to Call the Vet Right Away

Even if your cat seems “okay,” contact your vet if:

• Kittens or fragile cats: diarrhea lasts more than 24-48 hours.
• Adult cats: diarrhea lasts more than two to three days or keeps returning.
• Your cat stops eating, hides, or acts very differently from normal.
• There is any concern about toxins, foreign objects, or pre-existing health issues (like kidney disease or diabetes).

Prompt care can prevent complications like severe dehydration or organ damage.

How Vets Diagnose the Causes of Cat Diarrhea

History and Physical Exam

Your vet will start by asking questions such as

• When did the diarrhea begin?
• Any new food, treats, or stressors?
• Indoor-only or outdoor access?
• Any vomiting, weight loss, or other symptoms?

They will perform a full physical exam, including abdominal palpation, checking hydration, temperature, and body condition.

Diagnostic Tests

Depending on the case, tests may include:

• Fecal exam to look for worms, eggs, or protozoa like Giardia and coccidia.
• Bloodwork and urinalysis to assess organ function, thyroid levels, hydration, and signs of wider illness.
• Imaging (X-rays, ultrasound) to look for foreign bodies, thickened intestines, masses, or enlarged organs.
• Allergy or diet trials to see if a food sensitivity or allergy is causing your cat’s diarrhea.
• Endoscopy or biopsy to confirm IBD or rule out cancer.

Treatment Options for Cat Diarrhea

For mild, acute diarrhea in an otherwise healthy adult cat, your vet may recommend:

• Short-term diet adjustment (e.g., an easily digestible prescription diet).
• Careful monitoring of hydration and litter box use.
• Temporary reduction of treats and rich foods.

Never change food or fast your cat for long without veterinary guidance, especially in kittens or cats at risk for fatty liver disease.

Depending on the diagnosis, treatment may include:

• Dewormers for intestinal parasites.
• Antibiotics are used when a bacterial infection is strongly suspected or confirmed.
• Anti-inflammatory or IBD medications (e.g., steroids, other immune-modulating drugs) for chronic inflammatory conditions.
• Probiotics and gut-support supplements to help restore healthy gut bacteria.

Severe cases, especially in kittens, seniors, or cats with vomiting and not eating, may need:

• Fluids given intravenously to restore hydration and correct electrolyte changes
• Injectable medications for nausea, pain, or infection
• Close monitoring in the clinic

What You Can (and Shouldn’t) Do at Home

Safe Home Care Steps

While you are waiting for your vet appointment or following their plan:

• Keep fresh water available at all times.
• Feed exactly as directed, including prescription diets and portion sizes.
• Clean the litter box daily and track stool texture, colour, frequency, and any blood or mucus.
• Give all medication exactly as prescribed and finish the full course unless your veterinarian tells you otherwise.

Things to Avoid

• Do not give human anti-diarrheal medication, including loperamide, unless your veterinarian specifically approves it.
• Do not make sudden diet changes on your own.
• Do not withhold food for a long time without veterinary advice.

How to Prevent Diarrhea in Cats

• Change food gradually over 7 to 10 days.
• Feed a consistent, good-quality diet suited to your cat’s age and health.
• Avoid table scraps and sudden increases in treats.

• Keep up with deworming and flea control as recommended by your veterinarian.
• Have stool samples checked regularly, especially for kittens or outdoor cats.
• Keep routines and environments as stable as possible.

• Introduce new pets, people, or changes gradually.
• Provide hiding spots, vertical spaces, and daily playtime to help your cat feel secure.

Annual or semiannual checkups help catch chronic conditions, like hyperthyroidism, kidney disease, or IBD, before severe diarrhea and weight loss develop.

FAQs About Cat Diarrhea

1. How long should I wait before taking my cat to the vet for diarrhea?
   If diarrhea lasts more than 24-48 hours in kittens or fragile cats, or more than two to three days in healthy adults, call your vet. Go sooner if there is blood, vomiting, lethargy, or if your cat stops eating.
2. Can stress alone cause diarrhea in my cat?
   Yes. Stressful events like moving, new pets, or changes in routine can trigger stress colitis and diarrhea, especially in sensitive cats.
3. Is it normal for my cat to have diarrhea after switching foods?
   Mild, short-term soft stools can happen with diet changes, especially if the switch was sudden. But watery diarrhea that contains blood or lasts more than a couple of days is not normal and needs a vet check.
4. What should I feed my cat when it has diarrhea?
   Use the diet your veterinarian recommends. In many cases, that may be a highly digestible prescription diet or a carefully planned temporary feeding option. Avoid unapproved home remedies or sudden food experiments.
5. Can kittens get diarrhea more easily than adult cats?
   Yes. Kittens are more vulnerable to parasites, infections, and dietary upsets. They can become dangerously dehydrated very quickly, so any diarrhea in a kitten should be taken seriously. 

When is cat diarrhea dangerous?
Diarrhea is dangerous when it’s severe, bloody, combined with vomiting, or associated with lethargy, not eating, or dehydration, especially in kittens, seniors, or cats with other health issues. In these cases, contact your veterinarian or an emergency veterinary clinic promptly.