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Cat Diarrhea


When Diarrhea Strikes

Diarrhea is defined as increased fluidity of the feces, often accompanied by increased stool volume and frequency.

As a cat lover, you probably know what this means. Soft, stinky bowel movements adorning the litter pan—or worse, your carpet. The bad news: Diarrhea is a common symptom in cats. Food changes, infection, or prescribed antibiotics are common causes. The good news: most cases are mild and self-limiting. Some knowledge of the causes and treatment of diarrhea can help you be better prepared when diarrhea strikes.

Veterinarians typically classify diarrhea based on its duration, anatomic location, and severity. These characteristics can help narrow down the possible causes. Your veterinarian assess if the diarrhea is:

Acute vs. Chronic

Acute diarrhea is common. It has a fairly sudden onset and lasts a week or less. The most common causes of acute diarrhea include dietary intolerance, viral infections, and intestinal worms. An abrupt diet change can give a kitty the runs. So can dairy products, since contrary to popular opinion, many cats are lactose intolerant. Because a cat’s emotions can easily translate into physical problems, a stressful event—a change in your schedule, or a move to a new home—can trigger diarrhea.

Diarrhea is considered chronic if it persists for three weeks or longer despite treatment, or recurs repeatedly over time. Chronic diarrhea can be associated with certain parasites, food allergies, inflammatory bowel disease, pancreatic disorders, and systemic conditions such as thyroid disease.

Small vs. Large Intestinal

The type of symptoms your cat is having can pinpoint the problem area. Diarrhea that originates from the small (upper) intestine is typically soft to liquid, foul-smelling, fairly voluminous, and variable in color. You may notice flatulence. Small intestinal diarrhea would not be expected to contain frank (readily apparent) blood. Food allergy, pancreatic insufficiency, and inflammatory bowel disease are common afflictions of the upper small intestine. A hyperthyroid cat can present with small intestinal diarrhea.


If you notice your cat showing discomfort in the litter pan, always take a moment to determine whether urine or feces are still being produced. A urinary blockage can be life-threatening in male cats. If in doubt, consult your veterinarian right away.

Diarrhea that originates from the large (lower) intestine is a different matter. Cats with colitis (large intestinal diarrhea) are plagued by frequent and sudden urges to defecate. The diarrhea may be liquid and explosive, coming out in small bouts. There may be streaks of blood or mucus in the stool. Your cat may strain to defecate, with only a few drips of stool coming out. It’s not uncommon for cats to vomit in the course of a bout of straining. Once finished, your cat may seem agitated and go tearing around the house as if being chased.

Common causes of colitis include giardia, other parasites, and inflammatory bowel disease. Note that cats can exhibit classic colitis symptoms and actually be constipated. Your veterinarian can usually determine this by simple physical exam.

Mild vs. Complicated

Many cases of feline diarrhea are mild and self-limiting. They respond well to simple treatment and home care. Other times, diarrhea can be part of a more complex medical picture. Fluid loss from diarrhea of any cause, especially when accompanied by vomiting, can rapidly lead to dehydration and serious health consequences. This is especially true in kittens and older cats. Chronic disorders of the small intestine typically cause weight loss and malnutrition as time wears on. Some forms of acute diarrhea can be life-threatening and require aggressive intervention. These include feline distemper (panleukopenia), intoxications, and intestinal obstruction.

What To Do

Diarrhea is a nuisance at best. At its worst, it can be life-threatening. Contact your veterinarian right away if your cat’s diarrhea:

  • is accompanied by repeated vomiting, lethargy, loss of appetite, abdominal pain, generalized weakness, or fever.
  • contains large amounts of frank blood.
  • is black or tarry in color.
  • might be related to ingesting something toxic.
  • occurs in a kitten under nine months of age, particularly if vaccines were missed.
  • occurs in an elderly or medically frail animal.
  • fails to respond or gets worse despite 48 hours of symptomatic home care.

Causes of Kitty Diarrhea(Partial List)

Dietary Diarrhea

  • Diet Change
  • Food Intolerance or allergy(e.g. wheat gluten, fatty foods, dairy products)
  • Foreign Material
  • Toxins (e.g. lead)


  • Hookworms
  • Roundworms
  • Giardia
  • Coccidia
  • Tritrichomonas


  • Feline Distemper
  • Coronavirus/FIP


  • Salmonella Clostridium Campylobacter


  • Histoplasmosis

Systemic diseases

  • Pancreatitis
  • Liver disease
  • Kidney Disease
  • Hyperthyroidism
  • Diabetes Mellitus
  • FELV
  • FIV
  • Cancer


  • Inflammatory Bowel Disease (IBD)
  • Irritable Bowel Syndrome
  • Hemorrhagic Gastroenteritis (HGE)
  • Fiber-Responsive Diarrhea
  • Stress Colitis


  • Pancreatic Exocrine Insufficiency
  • Intestinal Obstruction
  • Intestinal Cancer


  • Lead
  • Plants

When healthy adult cats get a simple case of diarrhea, it’s often reasonable to try treating them at home. When in doubt, consult your veterinarian.

If you’ve recently changed your cat’s food, stop the new diet. Changing back to the old food for a few days can solve the problem. Otherwise, try feeding small, frequent meals of simple, easily-digested food such as low-fat chicken or beef, which can be pureed in a blender with water or chicken broth to yield a good consistency. Consider adding a probiotic such as lactobacillus, the “good bacteria” found in yogurt. Fortiflora is an excellent source of live, active probiotic cultures. Unflavored canned pumpkin, which is full of fiber, is a great way to firm up stools and has a taste that many cats like. One to two level tablespoons per 5.5 oz can of cat food is a good starting dose. Feed the sick diet until 48 hours past the resolution of diarrhea. Then slowly reintroduce a healthy maintenance diet over the next few days, taking care to avoid any pet foods or treats that may have triggered the problem in the first place.

Never give any medications, including over-the-counter human medications, to your cat unless under strict instructions by your veterinarian. Common over-the-counter remedies such as Pepto Bismol and Imodium, while safe for you, can be toxic for your cat. Inappropriate use of people medicine can make pets very sick.

If Your Cat Ends Up at the Vet’s

You can help by giving a thorough history. Be prepared with answers to the following questions:

  • Onset and duration of the diarrhea?
  • How many times per day?
  • Urgency, “accidents,” straining to defecate?
  • Blood or mucus in the feces?
  • Dietary history, including diet changes, treats?
  • What treatments, if any, has the cat been given and how did they work?
  • Other symptoms, including vomiting, lethargy, appetite loss?
  • Does your cat go outside?
  • Exposure to other animals that may have been sick?
  • Recent stressful events?
  • Current and past vaccinations?

Your vet will conduct a full physical examination, checking especially for signs of dehydration, anemia, abdominal pain, intestinal irregularities, fever, and weight loss. Your vet will most likely want to run a fecal analysis for parasites, so don’t forget to bring a fresh stool sample if available.

In simple diarrhea cases, the plan is usually straightforward. Your vet is likely to prescribe a special diet and/or medication, along with a dewormer if indicated. Sicker cats will need more involved workups such as labwork, xrays, specialized imaging, blood and fecal tests. Very sick kitties may need to be admitted to the hospital for IV fluids and intensive medical treatment. Some chronic diarrheas are ultimately managed through food and medication trials. Definitive diagnosis may require surgery or biopsy.

Sources and Further Reading:

  • 1. “Diseases of the intestines.” In Leib MS, Monroe WE (eds.). Practical Small Animal Internal Medicine. Philadelphia: WB Saunders, 1997.
  • 2. Sherding, RG & Johnson, SE. “Diseases of the Intestines.” In Birchard, SJ & Sherding, RG (eds.). Saunders Manual of Small Animal Practice. Philadelphia: W.B. Saunders, 2000.
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