Diarrhea can be caused by something as simple as a change in diet or getting into a garbage can, however much more serious illness or infection is also possible and needs to be rule out. Diarrhea may be sudden in onset and short in duration. It can also last for weeks to months or occur off and on. A single bout of diarrhea is generally not a cause for concern pets—but if it persists for more than a day, it can lead to dehydration, especially in small animals , may indicate an underlying health issue and should be checked out by a veterinarian.
What Are Some of the Causes of Diarrhea in Dogs?
• Change of diet
• Food intolerance
• Ingestion of garbage or spoiled food
• Ingestion of poisonous substances or toxic plant material
• Ingestion of foreign body (for example, toy, rubber band, plastic bag, etc.)
• Allergic reaction
• Bacterial or viral infection
• Parvovirus
• Internal parasites, such as hookworms, roundworms, whipworms, coccidia and giardia
• Inflammatory bowel disease
• Heart disease
• Kidney or liver disease
• Cancer or other tumors of the digestive tract
• Certain medications
• Colitis
• Stress
• Hemorrhagic gastroenteritis
What Are the General Symptoms of Diarrhea?
Loose or liquid, frequent stools are the most common symptoms of diarrhea. Other signs include flatulence, blood or mucus in stool, changes in volume of stool and straining to defecate. Lethargy, dehydration, fever, vomiting, decreased appetite, weight loss and an increased urgency to defecate may also accompany diarrhea.
If your pet’s diarrhea is black, he could be experiencing internal bleeding of the stomach or small intestine and should be examined by a vet immediately.
When Should I Take My Dog to the Vet?
Bring your pet to the vet if his diarrhea continues for more than a day, or if you observe lethargy, vomiting, fever, dark-colored or bloody stools, straining to defecate, decreased appetite or unexplained weight loss. Contact your veterinarian immediately if you notice your puppy or a toy or small breed dog has diarrhea, as it can be an important indicator of serious diseases in young dogs.
What Can I Expect at the Veterinary Hospital?
Your veterinarian will examine your pet for underlying illnesses and assess for dehydration. He or she may take a stool sample to check for the presence of internal parasites or clostridia, as well as conduct blood tests and radiographs to identify a possible cause of the diarrhea.
Other diagnostic tests might include ultrasound, special testing, cultures, endoscopy and biopsy. The diagnostic tests performed and treatment recommended will depend on how the long the diarrhea has been going on and the severity of your dog’s condition.
How Can I Prevent Diarrhea?

• Keep up to date with your pet’s vaccinations.
• Make sure your pet is free of parasites by following your veterinarian’s recommendations.
• Don’t let your pet have access to garbage, spoiled food, etc.
• When walking your dog, watch that he does not eat anything off the street, does not eat plant material or drink from puddles.
• Minimize stress in your pet’s environment.
• If you decide to switch your pet’s food, it’s a good idea to introduce it gradually, mixing it with his current food to ensure an easier transition for your pet’s GI tract.
• You can use pet probiotics or plain white yogurt to keep your pet’s intestinal flora in good health.