Gastritis in Dogs: Symptoms, Causes & Treatment (2026)

What Is Gastritis?

Gastritis is inflammation of the gastric mucosa — the inner lining of the stomach. When the stomach lining becomes irritated or inflamed, it loses its ability to function normally: acid secretion becomes dysregulated, the protective mucus layer is disrupted, and the stomach empties less efficiently. The result is nausea and vomiting.

Gastritis in dogs is broadly divided into two categories:

• Acute gastritis: Sudden onset, typically from a dietary cause. Self-limiting in most cases — the stomach irritation resolves within 24–48 hours with minimal or no treatment.
• Chronic gastritis: Recurring or persistent inflammation lasting weeks to months. Requires investigation to identify the underlying cause, which may be systemic rather than primarily gastric.

Gastritis is one of the most common GI complaints in dogs. Most cases are mild and straightforward. But recurring or severe vomiting is worth taking seriously — it can be the first sign of an underlying disease that has nothing to do with the stomach itself.

Signs and Symptoms

The cardinal sign of gastritis is vomiting. The character of the vomit often provides a clue:

• Undigested or partially digested food — suggests vomiting shortly after eating
• Yellow-green bile or froth — stomach is empty; bile reflux from the small intestine is irritating the stomach. Common in dogs that skip meals or vomit first thing in the morning.
• Digested "coffee grounds" material or frank red blood — indicates bleeding in the stomach or upper GI tract. Requires prompt veterinary attention.

Other signs of gastritis include:

• Lip-licking and repeated swallowing — behavioral signs of nausea
• Grass-eating — dogs often eat grass when nauseated, which typically induces vomiting
• Reduced appetite or complete refusal of food
• Hunched posture or reluctance to move — suggests abdominal discomfort
• Lethargy
• Excessive drooling (hypersalivation) in some dogs

In chronic gastritis, the pattern is intermittent — the dog vomits periodically over weeks or months, often with progressive weight loss and a gradual decline in appetite. The dog may appear relatively normal between episodes, making the underlying problem easy to dismiss.

Causes of Gastritis in Dogs

Acute Gastritis

The overwhelming majority of acute gastritis cases result from something the dog ate. Common culprits:

• Garbage, spoiled food, or scavenged material (bacteria, molds, and toxins)
• Fatty or rich foods — table scraps, grease, or high-fat treats can cause significant stomach irritation and carry a risk of pancreatitis
• Foreign material — plastic, fabric, bone fragments, grass, or plant material
• Sudden dietary change — switching foods abruptly disrupts the gastric environment
• Medications — NSAIDs (aspirin, ibuprofen), corticosteroids, and certain antibiotics irritate the gastric mucosa
• Viral or bacterial infections — parvovirus, distemper, Salmonella, Campylobacter
• Stress — boarding, travel, or other acute stressors can trigger transient gastric upset

Chronic Gastritis

Recurrent or persistent gastritis requires a broader differential. Common causes:

• Food allergy or intolerance — an adverse immune or non-immune reaction to a dietary protein. Often causes intermittent vomiting alongside skin signs (itching, ear infections).
• Inflammatory bowel disease (IBD) — immune-mediated inflammation of the GI tract. Can affect the stomach alone or in combination with the intestines. Requires biopsy for definitive diagnosis.
• Helicobacter infection — spiral bacteria that colonize the stomach lining. Their significance in dogs is debated; they are commonly found in healthy dogs too, but may contribute to chronic gastritis in some individuals.
• Parasites — Physaloptera (stomach worm) can cause chronic vomiting and is often missed on routine fecal tests because it does not shed eggs continuously.
• Kidney disease — uremic toxins irritate the gastric mucosa. Chronic vomiting is a classic sign of renal failure.
• Liver disease — hepatic dysfunction impairs toxin clearance, causing GI upset.
• Addison's disease — hypoadrenocorticism in dogs can present almost exclusively as GI signs, with vomiting and diarrhea as the primary complaint. It is frequently misdiagnosed as primary GI disease.
• Hyperthyroidism — rare in dogs (unlike cats), but worth considering in older dogs with unexplained GI signs.
• Gastric neoplasia — gastric tumors (adenocarcinoma, lymphoma, leiomyoma) can cause chronic vomiting, particularly in older dogs. Usually associated with progressive weight loss and anorexia.

What Bloodwork Shows

In simple acute gastritis, bloodwork is often completely normal. The value of running a panel is ruling out systemic causes — not confirming gastric inflammation itself, which requires endoscopy to visualize directly.

For chronic vomiting, the workup typically goes beyond a basic panel: cobalamin (B12) and folate levels assess small intestinal absorption; a Spec cPL or SNAP cPL test evaluates the pancreas; urinalysis adds context on kidney function; fecal tests look for parasites; and abdominal imaging (X-rays or ultrasound) can identify foreign bodies, masses, or organ abnormalities that bloodwork alone cannot detect.

How Vets Diagnose Gastritis

Acute Gastritis

For a dog with a single episode of vomiting and a history of eating something inappropriate, the diagnosis is largely clinical. The vet will assess hydration, pain, and whether the dog is otherwise well. Bloodwork may be run to rule out complications, but many straightforward cases are managed without extensive testing.

Chronic Gastritis Workup

Recurring vomiting warrants a systematic investigation. The typical sequence:

Treatment

Acute Gastritis at Home

For mild, single-episode vomiting in an otherwise healthy adult dog:

• Brief food rest: Withhold food for 4–6 hours to let the stomach settle. Do not fast small dogs or puppies for longer — they are at risk of hypoglycemia. Water should remain available.
• Bland diet: Offer small, frequent meals of boiled chicken (no skin) and plain white rice, or a prescription GI diet (Hill's i/d, Royal Canin GI). Feed 3–4 small meals per day rather than one or two larger ones.
• Gradual transition: Once the dog has been vomiting-free for 48 hours on the bland diet, gradually mix in normal food over 3–5 days.
• Hydration: Monitor for signs of dehydration (skin tent, dry gums, sunken eyes). A dog that cannot keep water down needs IV fluids at a vet clinic.

Veterinary Treatment

When the dog needs veterinary care, treatment is matched to severity and underlying cause:

Treating Chronic Gastritis

Treatment for chronic gastritis targets the identified cause:

• Food allergy/intolerance: Hydrolyzed protein or novel protein elimination diet for 8–12 weeks. Requires strict adherence — even treats must change.
• IBD: Immunosuppressive therapy (prednisolone, sometimes combined with azathioprine or chlorambucil) after biopsy confirmation.
• Helicobacter: Triple therapy — amoxicillin, metronidazole, and a proton pump inhibitor — for 2 weeks. Evidence for clinical benefit in dogs remains mixed.
• Kidney disease: Managing the underlying CKD (diet, phosphorus binding, anti-nausea medication) reduces gastric inflammation secondarily.
• Addison's disease: DOCP injections and prednisolone replacement — the GI signs typically resolve completely with appropriate hormone replacement.

Bilious Vomiting Syndrome

Some dogs vomit bile — yellow-green froth — first thing in the morning or after an extended period without food. This pattern is called bilious vomiting syndrome (BVS). It happens because bile refluxes from the small intestine into the empty stomach overnight, irritating the gastric lining.

BVS is generally benign. Dogs with this pattern are otherwise healthy, maintain their weight, and vomit only once (usually early morning). Management is straightforward: give a small snack at bedtime so the stomach is not empty overnight, or shift to twice-daily feeding if the dog currently eats once per day. If morning vomiting is frequent despite these changes, a short course of famotidine or a proton pump inhibitor may help.

If vomiting is more than once per day, involves food rather than just bile, or is associated with weight loss or behavioral changes, the cause is more likely chronic gastritis or another GI condition rather than BVS.

Prognosis

Acute gastritis carries an excellent prognosis. The vast majority of dogs recover completely with supportive care within 24–48 hours and do not require further treatment.

Chronic gastritis prognosis depends on the underlying cause. Food-responsive gastritis (dietary allergy or intolerance) carries an excellent prognosis — most dogs improve dramatically on an appropriate diet, and many can maintain remission long-term. IBD varies by severity and histopathologic subtype; many dogs are well managed on long-term immunosuppression. Gastritis secondary to systemic disease (kidney failure, Addison's) improves in parallel with management of the primary condition.

The most important factor is identifying the correct underlying cause early. A dog with Addison's being treated for “chronic stomach problems” without an ACTH stimulation test is not going to improve. A dog with IBD being fed a standard food rather than a hydrolyzed diet is not going to resolve. Getting the diagnosis right matters.