Gastroenteritis in Cats: Symptoms, Causes & Treatment

Last reviewed April 2026 · Veterinary reference article

Gastroenteritis vs. Gastritis vs. Colitis: What's the Difference?

All three conditions involve GI inflammation, and all three cause some combination of vomiting and diarrhea — but they affect different parts of the digestive tract and produce recognizably different patterns.

If your cat is vomiting repeatedly and having diarrhea at the same time, gastroenteritis — rather than isolated gastritis or colitis — is the likely pattern. The dual fluid loss from vomiting and diarrhea together makes gastroenteritis more acutely dangerous than either condition alone.

Symptoms of Gastroenteritis in Cats

The clinical picture combines upper GI signs (from the stomach) and small bowel signs (from the intestine):

• Vomiting — may contain food, bile (yellow-green fluid), or white froth; often multiple episodes
• Diarrhea — watery, loose, or semi-formed; typically large volume and less frequent than colitis
• Nausea signs — lip-licking, repeated swallowing, drooling, turning away from food
• Lethargy — variable; mild in dietary cases, pronounced in infectious or toxic causes
• Reduced appetite or anorexia
• Abdominal gurgling (borborygmi) or discomfort on palpation
• Dehydration — dry, tacky gums; skin tenting; sunken eyes in more severe cases

Dark, tarry stools (melena) indicate digested blood from higher in the GI tract. This is more concerning than fresh red blood and warrants prompt veterinary attention. See our guide on when GI signs become an emergency.

What Causes Gastroenteritis in Cats?

The most common causes are straightforward — a dietary change or something the cat shouldn't have eaten. But when symptoms are severe, persistent, or accompanied by blood, a broader list of causes needs to be considered.

Dietary Causes

Abrupt food changes disrupt the GI microbiome and can trigger vomiting and diarrhea within hours. The same applies to table scraps, dairy products, fatty foods, or eating too fast. Always transition to a new food over 7–10 days to minimize GI upset.

Parasites

Giardia is a common cause of small bowel diarrhea — often intermittent, pale, fatty, and malodorous. It requires a specific antigen test or PCR for diagnosis; routine fecal floats frequently miss it. Roundworms and hookworms can also produce mixed GI signs, particularly in younger or outdoor cats. In cats with persistent diarrhea, Tritrichomonas foetus is worth considering and requires PCR for diagnosis.

Viral Infections

Feline panleukopenia virus (FPV) — feline parvovirus — is the most serious viral cause of gastroenteritis in cats. It causes severe hemorrhagic vomiting and diarrhea, profound lethargy, and a dramatic drop in white blood cells (panleukopenia). Unvaccinated cats and kittens are at highest risk. FPV is highly contagious and often fatal without aggressive supportive care. Vaccination is highly effective.

Feline coronavirus (not FIP) can cause mild transient diarrhea in kittens but is rarely severe. Rotavirus and astrovirus have been identified in cats but are less well characterized.

Bacterial Infections

Salmonella and Campylobacter can cause vomiting, diarrhea (sometimes bloody), and fever. Sources include raw meat, contaminated food, and contact with infected animals or their feces. Salmonella in particular has zoonotic potential — human household members can be infected. Clostridium perfringens overgrowth is another cause of acute, often hemorrhagic diarrhea.

Toxins and Foreign Bodies

Ingestion of toxic plants (lilies cause acute kidney failure in cats — a separate emergency), cleaning products, certain medications, or spoiled food can cause acute gastroenteritis. Linear foreign bodies (string, thread, rubber bands) are particularly dangerous in cats — they can cause a characteristic "plication" of the intestine that is a surgical emergency.

Systemic Disease as a Cause

Chronic or recurring gastroenteritis may be the presenting sign of a deeper systemic condition. Pancreatitis in cats commonly presents with simultaneous vomiting and diarrhea (and sometimes jaundice). Inflammatory bowel disease (IBD) and intestinal lymphoma both cause chronic small bowel diarrhea, weight loss, and intermittent vomiting. Hyperthyroidism accelerates GI transit time and is a frequently overlooked cause of chronic diarrhea and vomiting in senior cats.

Hemorrhagic Gastroenteritis (HGE) in Cats

Hemorrhagic gastroenteritis (HGE) — now more precisely called acute hemorrhagic diarrhea syndrome (AHDS) — is a particularly dramatic form characterized by sudden-onset, profuse, bloody diarrhea with or without vomiting. Hematocrit (red blood cell percentage) rises sharply due to rapid fluid loss into the GI tract, making the blood abnormally concentrated (hemoconcentration) even as the cat is clinically compromised.

HGE is better characterized in dogs, but cats can be affected. It's a diagnosis of exclusion — other serious causes (panleukopenia, foreign body, intussusception, severe pancreatitis) must first be ruled out. Treatment is aggressive IV fluid resuscitation to correct hemoconcentration and prevent secondary organ injury.

How Vets Diagnose Gastroenteritis in Cats

For a healthy adult cat with mild symptoms and a plausible dietary cause (e.g., just ate something new), vets may take a watchful waiting approach with supportive care. But for more severe presentations, the following workup is typical:

If the workup points toward chronic disease rather than a self-limiting infection, the next step is endoscopy and intestinal biopsy — the only way to definitively diagnose IBD or differentiate it from intestinal lymphoma. These two conditions can look nearly identical on ultrasound but require very different treatment.

Treatment: What to Expect

Treatment depends heavily on the cause and severity. Here is what vets use across the range of presentations:

Managing Mild Cases at Home

If your cat has had one or two episodes of vomiting and a single soft stool, is still bright and alert, is drinking water, and has no blood in the vomit or stool, you may be able to monitor at home for 12–24 hours. Key steps:

1. Do not fast the cat for more than 4–6 hours — prolonged food withholding risks hepatic lipidosis in cats
2. Offer small, frequent amounts of a bland, easily digestible food — boiled chicken, plain rice, or a prescription GI diet
3. Ensure fresh water is available at all times; offer low-sodium chicken broth if the cat is reluctant to drink
4. Monitor stool consistency, frequency, and the presence of blood or mucus
5. Monitor for signs of dehydration: pinch skin on the scruff — it should snap back immediately; check gums for moisture
6. If no improvement within 24 hours, or if any worsening occurs, contact a vet

Feline Panleukopenia: The Serious One

Feline panleukopenia virus (FPV) is the cat equivalent of canine parvovirus — and like parvovirus in dogs, it is a medical emergency. The virus destroys the rapidly dividing cells lining the intestinal wall as well as bone marrow stem cells, leading to:

• Profuse, often hemorrhagic vomiting and diarrhea
• Severe lethargy and collapse
• Dramatic drop in white blood cell count (leukopenia — the "pan-leuko-penia")
• Secondary bacterial infections due to compromised immunity
• Hypothermia in advanced cases

Unvaccinated cats and kittens under 6 months are at highest risk. FPV is environmentally stable and can persist for months on surfaces. There is no cure — treatment is intensive supportive care (IV fluids, nutrition, antibiotics for secondary infection, antinausea medication). Mortality in unvaccinated kittens can exceed 90% without treatment.

Vaccination (FVRCP) is highly effective and is the single best protective measure. If an unvaccinated cat presents with bloody diarrhea, profound lethargy, and very low white cell count, panleukopenia must be ruled out immediately.

Preventing Recurrent Gastroenteritis

For cats with a sensitive GI tract or history of recurring gastroenteritis:

• Change diets slowly — new food should be introduced over 7–10 days by gradually increasing the proportion
• Feed consistent, scheduled meals rather than free-feeding — helps detect appetite changes early
• Keep lids on bins and restrict access to houseplants (many are toxic)
• Deworm regularly based on your vet's recommendation, especially in outdoor cats
• Keep vaccines current — particularly FVRCP which covers panleukopenia
• Address chronic stress — multi-cat households, environmental changes, and boredom are underrated GI triggers in cats

Frequently Asked Questions