Disclaimer: This article is for general informational purposes only and does not constitute veterinary advice. Always consult a licensed veterinarian for diagnosis and treatment of your dog's health conditions.
The Short Answer
Black, tarry dog poop - called melena - is usually a sign of digested blood originating from the upper gastrointestinal tract (stomach or small intestine). Unlike bright red blood in stool, which suggests lower GI bleeding, black stool indicates the blood has been digested before passing. This can be serious and warrants a prompt veterinary evaluation.
What Is Melena?
According to the Merck Veterinary Manual, melena refers to black, tarry feces that indicates bleeding in the stomach or small intestine. The dark color and sticky, tar-like consistency come from blood being broken down during digestion.
It's different from hematochezia, which is bright red blood in stool and indicates bleeding lower in the GI tract.
Common Causes of Black Dog Poop
The American Kennel Club identifies several possible causes of melena in dogs:
- Stomach ulcers - often caused by long-term use of NSAIDs (non-steroidal anti-inflammatory drugs) or other medications
- Intestinal parasites - hookworms in particular can cause dark, tarry stool with severe infections, per the Merck Veterinary Manual
- Foreign body ingestion - objects that cause internal injury
- Liver disease
- Kidney failure
- Addison's disease
- Tumors or polyps in the stomach or intestines
- Clotting disorders
Could It Be Something Else?
Before assuming the worst, consider whether your dog recently ate:
- Large amounts of red meat or organ meat (liver)
- Iron supplements
- Pepto-Bismol or other bismuth-containing medications
- Dark-colored treats or foods with food coloring
These can temporarily darken stool without indicating bleeding. However, if you're unsure of the cause, always err on the side of contacting your vet.
When Is Black Poop an Emergency?
Treat black tarry stool as urgent - same-day vet contact - if your dog also shows:
- Vomiting (especially if the vomit looks like coffee grounds)
- Weakness or collapse
- Pale or white gums
- Loss of appetite
- Rapid breathing
- Abdominal pain or bloating
Pale gums combined with black stool can indicate significant internal blood loss - this is an emergency situation requiring immediate veterinary care.
What to Tell Your Vet
When you call, be ready to describe: when you first noticed it, how many times your dog has passed black stool, any recent medications, what your dog has eaten, and any other symptoms. If possible, bring a fresh stool sample to the appointment.
Frequently Asked Questions
Is black dog poop always serious?
Not always - diet and certain medications can cause dark stool without indicating illness. But because melena can signal upper GI bleeding, it should always be evaluated by a vet if you can't clearly explain the color by something your dog ate or a medication they're on.
What's the difference between black poop and dark brown poop?
Normal dog stool can range from medium to dark brown. Melena is distinctly black with a sticky, tar-like consistency - not just darker than usual. If you're not sure, press a piece of tissue against the stool: melena will leave a reddish-black smear.
Can hookworms cause black stool?
Yes. According to the Merck Veterinary Manual, severe hookworm infections can cause diarrhea with dark, tarry feces along with anemia and weakness.
