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Key takeaways

Diarrhea, or loose/watery stool, is a common symptom of many conditions in dogs which range from transient and non-serious to life-threatening.

  • Diarrhea ranges in form and severity, and may contain blood, mucus, fat, visible parasites, or foreign matter
  • Common diagnostic testing for dogs with diarrhea includes fecal analysis for pathogens and intestinal parasites as well as specific viral testing where indicated
  • Simple cases of diarrhea are commonly treated symptomatically without making a diagnosis of the underlying cause
  • Complicated cases may require a more aggressive diagnostic approach including bloodwork, diagnostic imaging, endoscopy, and biopsies
  • Common symptomatic treatment includes fasting, rehydration, bland diets, and probiotics/digestive supplements
  • Specific therapy depends on the underlying cause of the diarrhea and commonly includes anti-parasitic or antibiotic medication, anti-inflammatory medication, pancreatic enzyme supplementation, and diet change
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A closer look: Diarrhea in Dogs

Diarrhea varies in severity and seriousness. Most cases of diarrhea in fully-vaccinated young adult dogs who are otherwise healthy are dietary in origin and are usually self-limiting. If diarrhea persists for an extended period of time, it may lead to dehydration and warrants veterinary investigation. Characteristics of diarrhea are useful for determining if it is originating from the small or large bowel (colon).

Large bowel diarrhea is characterized as showing:

  • Frequent urge to defecate
  • Passage of small amounts of stool
  • Straining to defecate (tenesmus)
  • Mucus in stool
  • Hematochezia (red/fresh/frank blood in stool) Small bowel diarrhea typically shows:
  • Normal to increased frequency
  • Passage of large volumes of stool
  • No straining, mucus, or urgency
  • Black blood (melena), if present

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Possible causes

Dogs often have diarrhea in response to something in the diet, including:

  • A novel food
  • Something rich or fatty
  • Overindulgence
  • Spoiled food
  • Toxins (including toxic foods like chocolate)
  • Foreign object or non-food substance in the gastrointestinal tract.

Other common reasons dogs may experience watery diarrhea include:

In addition, viral infections, autoimmune diseases, food sensitivities and/or allergies, and some endocrine disorders may present with diarrhea.

Risk factors

Diarrhea may be acute or chronic and vary in severity and characteristics depending on the cause. Diarrhea also occurs due to a variety of other conditions, some of which are serious or even life-threatening. Diarrhea in an otherwise healthy dog that lasts for more than 2 - 3 days warrants veterinary attention. Diarrhea accompanied by other symptoms deserves more urgent care. Diarrhea presenting with severe symptoms like these is an emergency:

Abrupt onset of bloody diarrhea characterized by the frequent passage of small amounts jelly-like clumps of red blood is the hallmark of acute hemorrhagic diarrhea syndrome (HGE) which is an emergency. This is more common in small or toy breed dogs.

Testing and diagnosis

Diagnostic tools for diarrhea in dogs include:

  • History, including notes about typical bowel movements
  • Physical examination
  • Fecal analysis
  • Blood tests
  • Ultrasound or X-ray imaging of abdomen
  • Endoscopy
  • Tissue biopsy Treatment varies depending on the diagnosis and severity of the condition. Dogs with severe diarrhea are often dehydrated and require fluid therapy.

Common symptomatic therapy strategies for diarrhea include:

  • Fasting
  • Fluid therapy
  • Small, frequent feedings of a bland diet, such as plain white rice and natural yogurt
  • Dietary supplementation with plain pumpkin (note: NOT seasoned pumpkin pie filling)
  • Probiotics and digestive supplements
  • Anti-diarrheal medication
  • Supportive/nursing care
  • Vitamin supplements (B12)

Specific anti-diarrheal therapy based on the diagnosis often includes:

  • Antibiotics
  • Anti-inflammatories
  • Immunosuppressive medication
  • Anti-parasitic medication
  • Therapeutic diets
  • Fiber supplements
  • Enzyme supplements

Note: always consult a veterinarian before making dietary changes or supplementing the diet. Many supplements available for pets are neither effective nor safe.

Similar symptoms

Diarrhea is self evident and not likely to be mistaken for other symptoms. Bowel incontinence may accompany diarrhea. Straining to defecate (tenesmus) often occurs with diarrhea. Straining to defecate is frequently misinterpreted as indicative of a bowel obstruction when it is actually rarely associated with that condition.

Associated symptoms


Jörg M. Steiner, Med Vet, Dr Med Vet, PhD, DACVIM-SAIM, DECVIM-CA, AGAF - Writing for Merck Veterinary Manual
Alex Gallagher, DVM, MS, DACVIM-SAIM - Writing for Merck Veterinary Manual
Joseph Taboada, DVM, DACVIM - Writing for Merck Veterinary Manual
Andrew S. Peregrine, BVMS, PhD, DVM, DEVPC, DACVM-Parasitology - Writing for Merck Veterinary Manual
Wendy Brooks, DVM, DABVP - Writing for Veterinary Partner
Tony Johnson, DVM, DACVECC - Writing for Veterinary Partner
Wendy Brooks, DVM, DABVP - Writing for Veterinary Partner
Wendy Brooks, DVM, DABVP - Writing for Veterinary Partner
Christine Calder, DVM, DACVB - Writing for Veterinary Partner
Frédéric Gaschen,, Dr.habil., DACVIM, DECVIM-CA - Writing for Veterinary Partner
Frédéric Gaschen,, Dr.habil., DACVIM, DECVIM-CA - Writing for Veterinary Partner
Wendy Brooks, DVM, DABVP - Writing for Veterinary Partner

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