Black Tar Stool (Melena) in Dogs: Why It’s Dangerous

Noticing a sudden change in your beloved dog's stool can be alarming. Black tarry stool—called melena—usually means digested blood from the upper GI tract (the stomach or the upper small intestine) and is a sign that needs prompt attention.

Melena in dogs is a symptom, not a diagnosis. Common causes include gastric ulcers, swallowed foreign objects, parasites, toxins, or tumors — any of which can lead to internal bleeding. If you spot black, sticky, tar-like stool, take action right away.

When to act

If the stool is very dark or tarry, follow these steps immediately — doing so helps your vet triage and treat your dog faster.

• Photograph the stool clearly in daylight and, if safe, collect a fresh sample in a clean container.
• Note the exact time you first saw the change and any recent food, treats, or medications your dog had.
• Call your vet and describe the color, consistency, and any other symptoms (vomiting, weakness, pale gums).

If your dog is collapsing, very weak, has repeated vomiting (especially with blood), or shows pale gums, go to an emergency clinic right away rather than waiting for a routine appointment.

For more background on causes, signs, and possible treatment, see our full guide: why your dog's stool is black. Keeping an eye on stool color and consistency is one of the simplest ways to protect your pet's health.

Key Takeaways

• If you see black, tarry stool (melena), call your vet immediately — it often indicates upper GI bleeding and can be an emergency.
• Possible causes include ulcers, swallowed foreign bodies, parasites, toxins, and tumors; the correct treatment depends on the underlying cause.
• Watch for emergency signs: pale gums, repeated vomiting (especially with blood), weakness or collapse, and major loss of appetite or energy.
• What to bring to the clinic: a fresh stool sample or a clear photo, the time you first noticed the change, and a list of any recent foods, treats, or medications.
• Common diagnostic steps include fecal analysis (parasite checks and occult blood tests), bloodwork (CBC and chemistry), and imaging or endoscopy to locate lesions or foreign objects.
• Treatment can range from gastroprotectants and deworming to IV fluids or surgery — follow your veterinarian’s guidance for follow-up and ongoing care.

Understanding Black Tarry Stool in Dogs

Melena (black tarry stool) is more than a simple change in your dog's poop color — it usually signals digested blood from the upper digestive tract. True melena is typically very dark, sticky, and has a tar-like consistency, which means blood was exposed to stomach acid and partially digested before it passed.

Seeing black tarry stool can be frightening. Remember: melena is a symptom, not a diagnosis — it tells your vet where to look (most often the stomach or the upper small intestine) but not why the bleeding started.

How melena forms

When blood enters the stomach or upper small intestine, acid and digestive enzymes change its color and texture. The result is dark, foul-smelling stool rather than bright red blood, which usually indicates fresh bleeding from the lower gut.

How to tell melena from other dark stools:

• Color and consistency: melena is very dark to black and tacky or tar-like.
• Odor: digested blood often smells stronger or more unpleasant than routine dog poop.
• Context: recent ingestion of iron supplements, bismuth-containing products, or dark-colored foods can darken stool without bleeding — note any diet changes.

Two short examples to keep in mind:

• If your dog accidentally ate an iron supplement and you see dark stool afterward, tell the vet about the supplement — the color change may not be bleeding.
• If your dog has been on NSAIDs (human ibuprofen or similar) and then develops black, sticky stool, that combination raises concern for gastric erosion or ulcer and needs veterinary evaluation.

Common medical causes include stomach ulcers, erosions from medications, foreign objects that damage the GI lining, parasites (heavy infestations), and tumors. If you notice a troubling change in your dog's stools for more than one bowel movement — especially with vomiting, diarrhea, pale gums, or lethargy — photograph the stool, collect a fresh sample if safe, note the time you first saw the change, and call your vet.

The Dangers of Melena

Melena in dogs is a warning sign that your pet may be losing blood somewhere in the digestive tract. Black, tarry stool typically means blood was partially digested as it passed through the stomach or upper small intestine — a red flag that deserves timely veterinary evaluation.

Not every case of dark stool is life-threatening, but melena can indicate serious problems such as gastric ulcers, tumors, severe gastritis, or toxin exposure. Left untreated these conditions can cause significant internal bleeding, anemia, and shock.

Quick steps to take now

• Record the time you first noticed the change and any recent medication or diet changes.
• Capture evidence: photograph the stool in daylight and, if safe, collect a fresh sample in a sealed container.
• Call your vet to describe the stool color and any other symptoms — if your dog is weak, collapsing, vomiting blood, or has pale gums, head to an emergency clinic immediately.

Emergency signs — seek immediate care

• Pale or white gums (a sign of anemia)
• Repeated vomiting, especially with blood
• Weakness, collapse, or difficulty breathing
• Very high heart rate or unresponsiveness

Example: if your dog vomits dark material and appears weak with pale gums, go to the emergency hospital now — don’t wait for a regular appointment.

For more on bloody stool in dogs, see this article. If you find black tarry stool in your dog's poop, contact your vet promptly — early diagnosis and treatment often improve outcomes and can be lifesaving.

Common Causes of Black Tarry Stool in Dogs

Melena in dogs can come from several sources — many involve bleeding in the gastrointestinal tract, medication effects, or something your dog swallowed. Knowing the likely causes helps you spot problems early and get the right care.

Internal bleeding and GI disease

Internal bleeding is the top concern when stool is black and tarry. Common medical causes include:

• Gastrointestinal ulcers or erosions (stomach or upper small intestine)
• Severe gastritis or inflammatory bowel disease
• Tumors or cancer in the gastrointestinal tract

These conditions produce melena because blood is partially digested as it moves through the stomach and upper intestine. Short example: a dog on long-term NSAIDs develops gastric irritation that progresses to an ulcer and black tarry stool.

Medications and supplements

Certain medications and high-dose supplements can either damage the stomach lining or change stool color. Notable points:

• NSAIDs (including human ibuprofen or naproxen) can cause gastric erosion — never give these to dogs; ask your vet for safer pain options.
• High-dose iron supplements and bismuth-containing products may darken stool without true bleeding — still report these exposures to your veterinarian.

Diet, foreign objects, and toxins

Dietary factors and ingestion events matter too. Extremely fatty or spoiled foods can trigger pancreatitis or gastritis in some dogs, which occasionally leads to bleeding.

Foreign objects (bones, toys, sharp items) can lacerate the intestinal lining and produce bleeding that shows up as dark or bloody stool. Certain toxins and poisons, notably some rodenticides, can cause coagulopathy (bleeding disorders) and lead to melena — if you suspect toxin ingestion, contact your vet or an emergency clinic right away.

Parasites and infections

Heavy parasite burdens — for example, hookworm or whipworm infestations — can cause intestinal blood loss visible in the stool. Bacterial or viral infections that damage the GI lining may also result in dark or bloody stools.

• Gastrointestinal ulcers
• Inflammatory bowel disease
• Gastritis
• Tumors or cancer in the GI tract
• Parasites (e.g., heavy hookworm infestations)

Practical checklist for the vet visit: note recent food or treats given, list all medications or supplements, mention any possible trash or toxin access, and bring a fresh stool sample or a clear photo with the time you first noticed the change.

Prevention tips: keep trash and toxic substances out of reach, avoid feeding large amounts of fatty table scraps, store medications securely, and maintain parasite prevention as recommended by your vet. If you see black tarry dog stool or other worrying changes in your dog's stools or behavior, schedule a vet visit promptly — early evaluation helps determine the cause and guide treatment.

Diagnostic Procedures for Melena

Finding the cause of black tarry stool requires a stepwise approach so your vet can pinpoint the source of bleeding and plan appropriate treatment. The process starts with a physical exam and a careful review of your dog's recent history — medications, diet changes, possible toxin or foreign-body exposure.

What your vet will test first

Initial diagnostics are quick and noninvasive and help decide whether more advanced tests are needed.

Fecal analysis and stool testing

Fecal analysis usually includes a parasite screen and a fecal occult blood test (FOBT).

• What it reveals: shows intestinal parasites or occult (hidden) blood in the stool.
• Limitations: FOBT can miss intermittent bleeding and can be affected by some foods or supplements (for example, iron).

Bloodwork

Bloodwork — a complete blood count (CBC) and serum chemistry — evaluates overall health, detects anemia, and checks organ function.

• What it reveals: low red blood cell count suggests blood loss; BUN may be elevated with upper GI bleeding.
• Use: helps your vet decide if hospitalization, IV fluids, or transfusion are needed before advanced testing.

Imaging and advanced diagnostics

If initial tests don’t explain the melena, your vet may recommend imaging or referral.

• X-rays or abdominal ultrasound: look for foreign bodies, masses, or structural problems.
• Endoscopy: directly visualizes the stomach and upper small intestine, allows biopsy or retrieval of objects, and is often the single most informative test for upper GI lesions.

Example timeline

Typical staged workup:

• Day 1: exam, fecal tests, and baseline bloodwork.
• Day 2: imaging (X-ray/ultrasound) if needed; consider stabilization (IV fluids) before advanced tests.
• Day 3: referral for endoscopy or surgery if imaging suggests a mass or foreign body.

What to bring to the vet: a fresh stool sample (if possible), a clear photo of the stool, a list of all medications and supplements, and notes on when you first noticed the change.

Ask your clinic about expected turnaround times, likely costs, and whether your dog needs to fast before imaging or endoscopy. Some clinics stabilize with fluids or other emergency care before performing advanced tests.

These diagnostic steps help your veterinarian confirm true melena (digested blood from the upper GI tract) versus other causes of dark stool and then develop a prioritized treatment and monitoring plan for your dog.

Treatment Options for Dogs with Melena

Treating melena focuses on three goals: stop the bleeding, address the underlying cause (ulcer, parasite, foreign body, tumor, or toxin), and support recovery. Early veterinary intervention improves the chance of a good outcome.

Stabilization and emergency treatments

If your dog is anemic, dehydrated, or unstable, the clinic will prioritize stabilization.

• IV fluids to correct dehydration and support blood pressure.
• Blood transfusion in severe anemia to restore oxygen-carrying capacity.
• Pain control and anti-nausea medications to keep your dog comfortable while diagnostics proceed.

Medications

Vets commonly prescribe gastroprotectants and acid suppressants to protect the stomach lining and reduce further bleeding.

• Proton pump inhibitors (e.g., omeprazole) or H2 blockers (e.g., famotidine) to reduce acid and allow healing.
• Antibiotics or anti-inflammatory drugs if infection or inflammatory bowel disease is suspected (only under veterinary direction).
• Never give human NSAIDs (ibuprofen, naproxen) — they increase the risk of ulcers and bleeding. Ask your vet for safe alternatives for pain.

Dietary adjustments

A bland, easily digestible diet is often recommended during recovery. For chronic GI disease, your veterinarian may suggest a therapeutic diet higher in fiber or formulated for gastrointestinal health.

Consider probiotics or small, frequent meals while your dog recovers; discuss any diet or treats changes with your vet before switching.

Procedural and surgical options

If imaging or endoscopy finds a foreign object, mass, or lesion, removal may be necessary.

• Endoscopic retrieval can remove some foreign objects without surgery.
• Surgery may be needed for perforations, large masses, or objects that can’t be retrieved endoscopically.
• If cancer is diagnosed, options may include surgery, chemotherapy, or palliative care depending on the type and stage.

At-home care and follow-up

Follow your veterinarian’s instructions about medications, feeding, and activity restriction. Monitor stool color, appetite, energy level, and any vomiting.

What to expect at discharge: a medication list with clear dosing instructions, a feeding plan, and a recheck schedule (often within 1–2 weeks). If signs worsen — repeated vomiting (especially with blood), pale gums, fainting, or collapse — seek emergency care immediately.

Example care plans

Mild case: outpatient treatment with gastroprotectants, a bland diet, and close monitoring; recheck in 7–14 days.

Severe case: hospitalization for IV fluids and possible transfusion, endoscopy or surgery, and a longer recovery with multiple rechecks.

Because treatments vary by cause, your vet will create a prioritized plan, explain likely monitoring and side effects, and tell you when to escalate care.

Prevention Strategies for Black Tarry Stool

Preventing black tarry stool (melena) focuses on reducing things that damage the gastrointestinal tract: unsafe foods, toxins, parasites, and improper medication use. A few practical habits go a long way toward protecting your dog’s GI health.

Daily prevention checklist

• Feed a balanced diet: choose a complete, high-quality dog food appropriate for your dog’s age and life stage; avoid frequent table scraps and large amounts of fatty foods that can trigger stomach upset or pancreatitis.
• Use safe treats: pick vet-recommended treats and avoid giving human foods that are risky for dogs.
• Secure trash and toxins: keep chocolate, xylitol-containing items, grapes/raisins, and spoiled food out of reach; store household chemicals and medications where pets cannot access them.
• Give medications responsibly: only administer drugs prescribed or approved by your vet. Never give human NSAIDs (ibuprofen, naproxen) — these can cause ulcers and GI bleeding.
• Maintain parasite prevention: stick to recommended parasite control and regular fecal checks, since heavy burdens (for example, hookworms) can cause intestinal blood loss.

Practical examples and tips

Safe treat examples: plain, small pieces of cooked chicken or commercial treats labeled for dogs. If your dog needs a special GI diet, work with your veterinarian to choose the right formula.

Common toxic items to watch for: xylitol (in sugar-free gum and some peanut butters), chocolate, grapes/raisins, and fatty leftovers. If you suspect toxin ingestion, contact your vet or an emergency poison helpline immediately.

When to book preventive care

Schedule routine veterinary checkups at least annually for healthy adults and more often for puppies or seniors. If it’s been over a year since your dog’s last exam, book a visit — your vet can review diet, parasite prevention, and medication safety.

Simple daily steps — feeding appropriate foods, securing toxic items, following medication guidance, and maintaining parasite prevention — significantly lower the risk of melena. Speak with your veterinarian about probiotics, specific parasite-control products, or dietary changes tailored to your dog’s needs.

Conclusion: Acting Quickly Matters

Black tarry stool (melena) in your dog is a potentially serious sign that should not be ignored. It can indicate ulcers, internal bleeding, or toxin exposure, and prompt veterinary care is usually needed to identify the cause and begin treatment.

If you notice melena or other worrying stool changes, call your vet right away. If your dog shows emergency signs — pale or white gums, repeated vomiting (especially with blood), severe weakness, collapse, or trouble breathing — go to an emergency clinic immediately.

Next steps

• Photograph the stool and, if safe, collect a fresh sample in a sealed container.
• Note the exact time you first saw the change and any recent food, treats, or medications.
• Call your clinic for advice; if your dog is unstable, transport to an ER for immediate care.

At the clinic expect a physical exam, fecal analysis and bloodwork, and possibly imaging or endoscopy. Some cases require hospitalization for IV fluids, transfusion, or surgery. Your veterinarian will explain the likely timeline for rechecks — often a 1–2 week follow-up for mild cases, sooner for severe ones.

Quick action and timely veterinary guidance give the best chance for a full recovery and help protect your pet's long-term health. For additional context on stool color and consistency, see veterinary care for melena.