Black Dog Poop: What Tarry Stool Means & When to Worry

Key takeaways

Black, tarry dog poop is called melena: partially digested blood, usually from the stomach or small intestine. It needs a same-day vet call.
Melena is shiny, sticky and foul-smelling. Poop darkened by blueberries, charcoal, iron or Pepto-Bismol keeps a normal shape.
Ulcers from pain relievers are a leading cause, and the FDA lists bloody or black stool as an NSAID side effect.
Rat poison typically causes bleeding 3 to 7 days after a dog eats it, so black stool days later still counts.
Black stool plus pale gums, coffee-ground vomit, weakness or collapse is an emergency.

Black dog poop deserves your attention today, not next week. True black, tarry, sticky stool (vets call it melena) usually means digested blood from the upper digestive tract, and that's a same-day vet call. Some dark stool is harmless, though. If your dog just ate a pile of blueberries or took Pepto-Bismol and the poop is dark but normally formed, you can usually watch the next one.

What does black dog poop mean?

Black dog poop usually means blood that was digested on its way through the gut. Fresh red blood points to the colon or rectum (our guide to dogs pooping blood covers that). Blood from higher up gets broken down along the way and comes out black.

The Cornell University College of Veterinary Medicine puts it plainly: "Black stool, officially called melena, is caused by partially digested blood." Cornell adds that the blood can come from the upper GI tract, the mouth or even the airways, so a bleeding mouth injury or a bloody nose can do it too.

What is tarry stool in dogs?

Tarry stool is melena: black, glossy, sticky poop that looks like wet road tar. MedlinePlus calls foul-smelling black or tarry stool a sign of a problem in the upper digestive tract, and lists blueberries, iron pills, activated charcoal and bismuth medicines as things that can turn stool black with no bleeding at all.

Clue:	Tarry Stool (Melena):	Diet-Dark Stool:
Color:	Jet black, often glossy	Very dark brown, black-green or gray-black
Texture:	Sticky, smeary, often loose	Normal, formed, picks up cleanly
Smell:	Unusually foul	Ordinary poop smell
Recent Trigger:	Pain meds, steroids, possible rat poison, chewed object	Blueberries, dirt or charcoal, iron, Pepto-Bismol
Your Dog:	May be tired, off food, vomiting, pale gums	Bright, eating, acting normal
What To Do:	Call your vet today	Watch the next stool; call if it's still black

What could be causing dark black poop in dogs?

Most true black stool traces back to bleeding in the stomach or small intestine. The Merck Veterinary Manual names NSAIDs, tumors and liver disease as the most commonly reported causes of stomach ulcers in dogs, with kidney disease, pancreatitis, foreign bodies and major trauma also on the list.

Cause:	Is It Serious?
Ulcers, often from NSAIDs or steroids	Yes, a leading cause
Swallowed blood from the mouth or nose	Varies; find the source
Swallowed objects scraping the gut	Yes, can worsen fast
Rat poison or a clotting disorder	Emergency
Stomach or intestinal tumors	Yes
Heavy hookworm infection (puppies)	Yes, can cause severe anemia
Pepto-Bismol, iron supplements	No, a known side effect
Blueberries, dirt, charcoal	No, passes quickly

Human pain relievers deserve their own warning. The FDA's guide to pain relievers for pets explains that ibuprofen, naproxen and aspirin can last longer and reach higher blood levels in dogs than in people, and can cause stomach and intestinal ulcers. Never give them to a dog. If black stool shows up while your dog is on a vet-prescribed NSAID, the FDA says to stop the drug and call your vet.

Swallowed objects are the other big one. A dog with black stool who's also vomiting or refusing food may have an intestinal blockage, and if vomiting keeps going, our guide on why dogs keep throwing up explains the next steps.

When is black dog poop an emergency?

Go to your vet or an emergency clinic right away if black stool comes with any of these:

Vomiting, especially with dark flecks that look like coffee grounds (digested blood, per MedlinePlus)
Pale, gray or white gums, a sign of blood loss
Weakness, lethargy or collapse
Refusing food or water
A tender belly, hunching or restlessness
Possible access to rat poison or human medication

For poison exposure, the ASPCA Animal Poison Control Center answers 24/7 at (888) 426-4435 (a consultation fee may apply).

One dark-but-formed stool in a bright, playful dog buys you a day of watching. Two black stools in a row, or one truly tarry one, does not.

Black dog poop but acting normal: should you worry?

Yes, if the stool is tarry. A dog who's eating and playing can still be bleeding, and Merck notes that some dogs with stomach ulcers show no clinical signs at all.

If it's dark but formed, think back over the last day. Did your dog raid the blueberries or dig through fire-pit ash? Those stools clear once the trigger passes. If you recently switched foods and the stool is also loose, Cornell's advice is to return to the old diet until it firms up, then transition to the new food more gradually. Mucus in the poop or soft stool alongside dark color is worth telling your vet about.

What will the vet do?

Expect a fecal exam, bloodwork for red cells and clotting, and possibly X-rays, ultrasound or endoscopy. In a Colorado State University review of 52 dogs with upper GI bleeding, blood urea nitrogen (BUN) averaged 31.0 mg/dL against 16.5 in control dogs, most likely because the gut absorbs nitrogen from digested blood. Treatment follows the cause: acid reducers for ulcers, surgery for a foreign object, deworming for hookworms, or vitamin K1, the antidote for anticoagulant rat poison.

Bring a photo of the stool or a fresh sample sealed in a bag, plus a list of every medication, supplement and treat from the past week.

What most black dog poop guides don't tell you

Pepto-Bismol can hide the bleeding you're worried about. Merck's chapter on diarrhea drugs warns that bismuth subsalicylate turns feces black and that "this color change may interfere with evaluating the feces for hemorrhage." Dogs also absorb practically all of its salicylate, an aspirin relative, and the FDA's NSAID guide for dog owners says never to give aspirin with an NSAID. Our take: skip the pink bottle for an upset stomach unless your vet okays it, and ask about a bland diet instead.

No black poop doesn't mean no bleeding. Merck calls melena "variable" in dogs with ulcers. In the Colorado State group, 11 of 52 bleeding dogs vomited blood but never passed melena.

"79% of dogs with upper GI bleeding (41 of 52) passed black, tarry stool; the rest only vomited blood, in a 1998 Colorado State University review." - Veterinary Clinical Pathology

Sometimes the gut isn't the problem. In a Tufts study of 55 dogs transfused for GI bleeding, 16 had immune-mediated thrombocytopenia, where the body destroys its own platelets. Rat poison blocks clotting from the outside, and Merck notes bleeding typically starts 3 to 7 days after a dog eats it. That's why vets check clotting along with the gut.

Frequently asked questions

Why is my puppy's stool black?

Take it seriously. Puppies handle blood loss poorly, and the Merck Veterinary Manual notes heavy hookworm infections cause dark, tarry stools and anemia that can be fatal in young pups. Call your vet the same day, especially with puppy diarrhea or low energy. See how to tell if your dog has worms for other signs.

Can food make my dog's poop black?

Yes. Lots of blueberries, eaten dirt or charcoal can darken stool for a day, and so can iron supplements and Pepto-Bismol. Food-darkened stool keeps a normal shape and smell, while melena is tarry, sticky and foul. If dark stool comes with diarrhea or your dog seems unwell, call your vet.

What's the difference between black poop and bloody poop?

Black, tarry stool is digested blood from the stomach or small intestine. Red blood, covered in our guide to bloody diarrhea in dogs, comes from low in the tract, usually the colon or rectum. Both deserve a vet call; the color tells your vet where to start looking.

What does a healthy dog poop look like?

According to VCA Animal Hospitals, healthy dog poop is chocolate brown, formed and segmented, and it should look about the same day to day. Our dog poop color chart explains green dog poop, yellow dog poop and other shades.

The bottom line: Black, tarry dog poop means digested blood until your vet says otherwise, so call the same day and treat pale gums or weakness as an emergency. A consistent diet makes changes easier to spot: Spot & Tango recipes are formulated with pet nutritionists to meet AAFCO standards and gently cooked from whole ingredients. Take the recipe quiz to build your dog's plan.

Questions about your dog's digestion or diet? Our customer care team is happy to help.

About this article

Written by the Spot & Tango editorial team, which covers canine nutrition and health for dog owners. Reviewed by a licensed veterinarian; facts and figures checked.

References & Sources:

Cornell University College of Veterinary Medicine, Riney Canine Health Center, Diarrhea (accessed 2026). https://www.vet.cornell.edu/departments-centers-and-institutes/riney-canine-health-center/canine-health-topics/diarrhea
Blois S., Gastrointestinal Ulcers in Small Animals, Merck Veterinary Manual (reviewed Jan 2025). https://www.merckvetmanual.com/digestive-system/diseases-of-the-stomach-in-small-animals/gastrointestinal-ulcers-in-small-animals
U.S. Food and Drug Administration, Get the Facts about Pain Relievers for Pets (accessed 2026). https://www.fda.gov/animal-veterinary/animal-health-literacy/get-facts-about-pain-relievers-pets
Dowling P., Drugs Used to Treat Diarrhea in Monogastric Animals, Merck Veterinary Manual (accessed 2026). https://www.merckvetmanual.com/pharmacology/systemic-pharmacotherapeutics-of-the-digestive-system/drugs-used-to-treat-diarrhea-in-monogastric-animals
Merck Veterinary Manual, Anticoagulant Rodenticide Poisoning in Animals (accessed 2026). https://www.merckvetmanual.com/toxicology/rodenticide-poisoning/anticoagulant-rodenticide-poisoning-in-animals
Prause L.C., Grauer G.F., Association of gastrointestinal hemorrhage with increased blood urea nitrogen and BUN/creatinine ratio in dogs, Veterinary Clinical Pathology (1998). https://pubmed.ncbi.nlm.nih.gov/12075537/
Waldrop J.E., Rozanski E.A., Freeman L.M., Rush J.E., Packed red blood cell transfusions in dogs with gastrointestinal hemorrhage: 55 cases (1999-2001), Journal of the American Animal Hospital Association (2003). https://pubmed.ncbi.nlm.nih.gov/14736715/
MedlinePlus (U.S. National Library of Medicine), Black or tarry stools (accessed 2026). https://medlineplus.gov/ency/article/003130.htm