Why Does My Dog Have Diarrhea? 3 Common Causes

Acute diarrhea comes on suddenly and typically lasts for a short period, usually less than 2-3 weeks. This type often resolves on its own or with basic home care. Acute cases generally represent a temporary disruption to your dog’s digestive system rather than a chronic condition.

• Loose, watery stool that may be difficult to pick up
• Increased frequency of bowel movements
• Urgency to defecate, sometimes accompanied by accidents in the house
• Normal energy levels and appetite in mild cases
• Duration of 1-3 days for uncomplicated cases

Chronic diarrhea persists for more than 2-3 weeks or occurs in recurring episodes over time. This type often indicates an underlying health condition that requires veterinary diagnosis and treatment. Chronic dog diarrhea shouldn’t be managed through home remedies alone.

• Persistent loose stools lasting weeks or months
• Weight loss over time
• Visible mucus or blood in the stool
• Lethargy or decreased energy levels
• Changes in appetite (either increased or decreased)
• Poor coat quality or other signs of nutritional deficiencies

Dietary issues represent the most common cause of dog diarrhea. Dogs are naturally curious and often consume things they shouldn’t, from garbage to toxic plants or foreign objects. Additionally, sudden changes in diet, even switching between high-quality dog foods, can trigger digestive upset as the intestinal bacteria need time to adjust to new ingredients. Many dogs also have specific food intolerances or allergies that can manifest as diarrhea.

Common Food Sensitivities That May Cause Dog Diarrhea

• Dairy products – Many dogs lack sufficient lactase enzymes to digest milk sugars properly, resulting in gas, bloating, and diarrhea after consuming dairy. Even small amounts of cheese or ice cream can trigger symptoms in sensitive dogs.
• Wheat and gluten – Some dogs have difficulty digesting these common ingredients found in many commercial dog foods and treats. Gluten sensitivity can cause chronic digestive issues that improve with elimination diets.
• Protein sources – Beef, chicken, egg, or other protein allergies can develop over time, even to ingredients your dog has eaten without problems in the past. These allergies often cause both gastrointestinal symptoms and skin irritation.
• Artificial additives – Colorings, preservatives, and flavor enhancers in low-quality dog foods can irritate sensitive digestive systems. Many dogs show improvement when switched to natural, additive-free diets.
• High-fat foods – Rich, fatty foods can overwhelm your dog’s digestive capacity and cause acute pancreatitis in some cases. Human foods like bacon, fried items, or fatty trimmings are particularly problematic.

Infectious agents, including bacteria, viruses, and parasites, commonly cause dog diarrhea. These pathogens can be contracted through contaminated food or water, contact with infected animals, or exposure to contaminated environments. Puppies are especially vulnerable to infectious causes of dog diarrhea due to their developing immune systems. Some infections, like parvovirus, can be life-threatening without prompt treatment.

Common Infections and Parasites That May Cause Dog Diarrhea

• Viral infections – Parvovirus is a highly contagious and potentially fatal virus causing severe, often bloody diarrhea, particularly in unvaccinated puppies. Coronavirus and distemper can also cause digestive symptoms alongside other clinical signs.
• Bacterial infections – Salmonella, E. coli, and Campylobacter can infect dogs through contaminated food or water. These bacterial infections often cause acute, severe diarrhea that may contain mucus or blood.
• Giardia – This microscopic parasite is commonly contracted from contaminated water sources like puddles or ponds. Giardia causes foul-smelling, mucusy diarrhea that often comes and goes over weeks or months.
• Intestinal worms – Hookworms, roundworms, and whipworms can all cause diarrhea in dogs of any age. Heavy parasite loads may cause visible worms in stool, weight loss, and anemia in severe cases.
• Coccidia – These single-celled parasites primarily affect puppies and immunocompromised dogs. Coccidiosis typically causes watery diarrhea that may contain blood and can lead to dehydration if left untreated.

Several ongoing health conditions can cause persistent or recurring dog diarrhea. These chronic issues typically require professional veterinary diagnosis, often including specialized testing or procedures. Management usually involves long-term medication, special diets, or other ongoing treatments to control symptoms and improve quality of life.

Common Digestive Conditions That May Cause Dog Diarrhea

• Inflammatory Bowel Disease (IBD) – This condition involves chronic inflammation of the digestive tract, which interferes with normal digestion and absorption. IBD requires lifelong management through diet, medication, and regular veterinary monitoring to control symptoms.
• Exocrine Pancreatic Insufficiency (EPI) – In this condition, the pancreas fails to produce sufficient digestive enzymes. Dogs with EPI typically have very loose, fatty stools and difficulty maintaining weight despite increased food consumption.
• Colitis – Inflammation of the colon causes recurring episodes of soft, mucus-coated stool, often with urgency and straining. Stress-induced colitis is common in high-strung breeds and may worsen during anxious periods.
• Small Intestinal Bacterial Overgrowth (SIBO) – An abnormal proliferation of bacteria in the small intestine interferes with proper digestion and absorption. SIBO typically causes chronic dog diarrhea, weight loss, and nutritional deficiencies despite normal or increased appetite.
• Lymphangiectasia – This uncommon condition involves the dilation of lymphatic vessels in the intestines, leading to protein loss. Affected dogs develop chronic diarrhea, weight loss, and fluid accumulation in the abdomen due to low protein levels.

Veterinarians use various tests to identify the underlying cause of persistent or severe dog diarrhea. These may include fecal examinations to detect parasites or bacterial infections, blood tests to check organ function and look for signs of infection, or imaging studies like X-rays or ultrasound to evaluate the digestive organs. In complex cases, endoscopy might be recommended to visually examine the intestinal lining and collect tissue samples for further testing.

When dog diarrhea leads to dehydration or electrolyte imbalances, fluid therapy becomes essential for recovery. Veterinarians may administer subcutaneous fluids for mild cases or intravenous (IV) fluids for more severe dehydration. These fluids help restore hydration, correct electrolyte abnormalities, and support overall organ function while the primary cause of diarrhea is being addressed.

Various medications may be prescribed based on the specific cause of your dog’s diarrhea. Antibiotics target bacterial infections, while antiparasitics eliminate intestinal parasites. Anti-inflammatory drugs help reduce inflammation in conditions like colitis or inflammatory bowel disease. For dogs with severe diarrhea, anti-diarrheal medications might be prescribed to slow intestinal motility and allow for proper absorption of nutrients and water.

Specialized prescription diets play a crucial role in managing many causes of chronic diarrhea. These diets are formulated to address specific digestive issues, such as food allergies, fat intolerance, or fiber requirements. Hydrolyzed protein diets break down proteins into smaller components that are less likely to trigger allergic reactions. High-fiber formulations help regulate intestinal motility, while low-fat options benefit dogs with pancreatic insufficiency or fat malabsorption.

Veterinarians often recommend specific probiotic supplements designed for dogs to restore healthy gut bacteria following diarrhea episodes. These beneficial microorganisms help normalize digestive function, strengthen the immune system, and prevent pathogenic bacteria from colonizing the intestines. For dogs with enzyme deficiencies, supplemental digestive enzymes may be prescribed to aid in breaking down food properly, improving nutrient absorption and reducing diarrhea.