Seeing that your dog has black tarry stool can be alarming, particularly when the feces look unusually dark, sticky, shiny, or almost like thick tar.
This appearance is different from ordinary dark-brown stool and is important to recognize because it can indicate a problem somewhere in the digestive tract.
The significance of black tarry stool depends on whether it happens once or repeatedly and whether your dog has other changes at the same time.
Vomiting, poor appetite, weakness, pale gums, abdominal discomfort, diarrhea, weight loss, or changes in normal behavior can make the situation more concerning.
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Dog Has Black Tarry Stool: Why It Happens
A dog can have black tarry stool when blood is digested as it passes through the upper gastrointestinal tract. This produces a type of stool called melena, which is typically very dark and may have a sticky or tar-like consistency.
However, not every black stool is caused by gastrointestinal bleeding. Certain foods, medications, supplements, and other substances can also make feces appear black.
The exact appearance of the stool and your dog’s other symptoms are therefore important when determining what the change may mean.
What Truly Tarry Stool Looks and Smells Like
Truly tarry stool in dogs is usually jet-black rather than dark brown, with a sticky, shiny, thick texture similar to road tar. It may smear easily when picked up and cling to grass or other surfaces.
The stool can also have an unusually strong, foul odor because it contains digested blood. This type of stool is known as melena and often indicates bleeding in the stomach or upper intestines.
Not every dark stool is melena. Foods, iron supplements, and certain medications can darken stool without causing bleeding, and odor alone cannot confirm the cause.
However, if your dog’s poop is genuinely black and tar-like, contact a veterinarian urgently, even if your dog seems well.
What Is Melena in Dogs?
Melena is the veterinary term for black, tarry stool caused by digested blood. When bleeding happens in the upper digestive tract (the esophagus, stomach, or first part of the small intestine), the blood travels a long way through the gut.
Digestive acids and enzymes break it down, and the iron in it turns the stool dark black with a sticky, tar-like texture.
True melena has a few hallmarks: a thick, glossy, almost wet appearance, a strong and unusually foul odor, and a sticky quality that makes it cling to grass or flooring. It can also be soft or loose.
Melena is a symptom, not a disease. It tells your vet that blood is being lost somewhere in the upper digestive system, and the next step is finding out why.
Even a small amount of ongoing blood loss can lead to anemia, which is why melena is treated as a reason to call a vet instead of waiting it out.
Dog Has Black Tarry Stool: Common Causes
Gastrointestinal Bleeding
Gastrointestinal bleeding is one of the most important causes of black tarry stool in dogs.
When bleeding occurs in the stomach or upper small intestine, the blood is exposed to digestive processes before it leaves the body. This can turn the stool black and give it the characteristic tar-like appearance.
A dog with gastrointestinal bleeding may also develop vomiting, reduced appetite, abdominal pain, weakness, lethargy, or pale gums.
The severity of these signs can vary depending on the amount and duration of blood loss.
Related: Black dog poop (Causes and treatment)
Stomach or Intestinal Ulcers
Ulcers can develop in the stomach or small intestine and may cause bleeding into the digestive tract.
When this blood is digested, it can produce black tarry stool. Dogs with gastrointestinal ulcers may also vomit, eat less, show abdominal discomfort, or become weak.
Certain medications and underlying diseases can increase the risk of gastrointestinal ulceration, making a veterinary assessment important when black tarry stool appears.
Related: Dog with cancer black poop (Causes and treatment)
Medication-Related Gastrointestinal Injury
Some medications can irritate the gastrointestinal tract or increase the risk of ulceration and bleeding.
This is particularly important when a dog has recently started a medication, had its treatment changed, or accidentally consumed medication intended for people.
If black tarry stool develops during medication use, contact your veterinarian. Do not stop prescribed medication or give additional medication without veterinary guidance.
Gastrointestinal Inflammation
Inflammation affecting the stomach or intestines can cause changes in bowel movements and may sometimes involve bleeding.
A dog may also develop vomiting, diarrhea, reduced appetite, abdominal discomfort, or lethargy.
If bleeding occurs higher in the digestive tract, the stool may become black and tar-like.
The underlying reason for gastrointestinal inflammation can vary, so the appearance of black stool alone cannot establish a diagnosis.
Dietary Indiscretion
Eating something unusual can change a dog’s stool color and consistency.
Garbage, spoiled food, rich foods, or other inappropriate substances can cause digestive upset. Certain dark foods may also temporarily make feces appear darker.
However, genuinely tarry stool should not automatically be blamed on something your dog ate, particularly if the change persists or other symptoms develop.
Certain Foods, Supplements, or Substances
Some substances can make feces look black without causing gastrointestinal bleeding.
Activated charcoal is one example. Certain foods and supplements may also change stool pigmentation.
This can make it difficult to determine the cause based solely on color. If the stool has a truly sticky, tar-like consistency, it is safer to discuss it with your veterinarian rather than assuming it is simply dietary discoloration.
Bleeding or Clotting Disorders
Problems involving the body’s ability to control bleeding can sometimes cause blood to enter the digestive tract.
A dog with a bleeding or clotting disorder may also develop unexplained bruising, nosebleeds, bleeding gums, or other signs of abnormal bleeding.
These conditions are less common, but they become more relevant when black tarry stool occurs together with bleeding elsewhere.
Swallowed Blood
Blood swallowed from another part of the body can sometimes result in black stool.
For example, a dog may swallow blood after a nosebleed, mouth injury, dental problem, or bleeding gums. Once swallowed, the blood can be digested and make the resulting feces appear black.
Tell your veterinarian about any recent bleeding because it can help determine where the blood may have originated.
A More Serious Gastrointestinal Disorder
Less commonly, black tarry stool can occur with more significant gastrointestinal disease.
Foreign objects, severe gastrointestinal inflammation, tumors, and other disorders can cause bleeding or injury within the digestive tract.
These conditions are not equally likely in every dog. Age, medical history, other symptoms, and examination findings help determine which possibilities need further investigation.
Related: Dog pooping bloody mucus but acting normal (Here’s why)
Dog Has Black Tarry Stool but Is Acting Normal
A dog with black tarry stool may still be eating, drinking, playing, and behaving normally.
While normal behavior is reassuring, it does not completely rule out gastrointestinal bleeding. Some dogs may show relatively subtle signs during the early stages of a digestive problem.
If the stool is genuinely black and tar-like, particularly if it happens again, contact your veterinarian even if your dog appears comfortable.
Dog Has Black Tarry Stool and Vomiting
Black tarry stool accompanied by vomiting can occur with gastrointestinal bleeding, ulcers, significant digestive irritation, medication-related complications, or other gastrointestinal disorders.
Black tarry stool accompanied by vomiting deserves immediate attention.
Repeated vomiting, inability to keep water down, abdominal pain, weakness, or rapidly worsening symptoms increase the urgency of veterinary assessment.
Dog Has Black Tarry Stool and Not Eating
Loss of appetite together with black tarry stool can be a sign that your dog is experiencing more than a simple stool-color change.
Dogs may stop eating because of nausea, abdominal discomfort, gastrointestinal inflammation, bleeding, or other illness.
If your dog refuses food and also develops vomiting, weakness, pale gums, abdominal pain, or repeated black stools, contact your veterinarian promptly.
Dog Has Black Tarry Stool and Diarrhea
Black, tarry stool combined with diarrhea can indicate bleeding in your dog’s digestive tract. As blood is digested while passing through the stomach or upper intestines, it can turn the stool black and sticky, a condition known as melena.
When the stool is also loose or watery, it may indicate gastrointestinal irritation or inflammation alongside the bleeding.
Possible causes include stomach ulcers, certain medications such as nonsteroidal anti-inflammatory drugs (NSAIDs), severe gastrointestinal disease, bleeding disorders, or other underlying illnesses.
Black, tarry diarrhea requires urgent veterinary assessment, even if your dog is still behaving normally. Seek emergency care if your dog also has vomiting, pale gums, weakness, rapid breathing, abdominal pain, or collapse, as these may indicate significant blood loss or a serious illness.
Do not give human anti-diarrhea medications or home remedies unless your veterinarian directs you to.
When to Call or Visit the Vet
Contact your veterinarian immediately if your dog has black tarry stool, particularly if the appearance is repeated or accompanied by other symptoms. Watch for:
- Repeated black or tar-like stools
- Vomiting
- Blood in the vomit
- Loss of appetite
- Significant lethargy or weakness
- Pale or unusually light-colored gums
- Abdominal pain
- A swollen or distended abdomen
- Frequent or severe diarrhea
- Signs of dehydration
- Weight loss
- Difficulty standing or walking
- Unexplained bruising or bleeding
- Suspected medication or toxin ingestion
- Suspected foreign-object ingestion
- Rapidly worsening symptoms
Seek urgent veterinary care if your dog collapses, becomes severely weak, repeatedly vomits, develops significant abdominal pain or swelling, or shows signs of substantial blood loss.
Dog Has Black Tarry Stool: Treatment
Treatment depends on the underlying cause. This may involve supportive care for dehydration or blood loss, management of gastrointestinal bleeding or ulceration, dietary management, treatment of gastrointestinal inflammation or infection, adjustment of medications when medically appropriate, or treatment of an underlying disease.
More serious cases may require hospitalization, blood-loss support, removal of a foreign object, surgery, or other disease-specific treatment.
Key Takeaway
A dog that has black tarry stool may be experiencing melena, in which digested blood causes the feces to become very dark and sticky.
This is different from ordinary dark-brown stool and can indicate bleeding in the stomach or upper small intestine.
Not every black stool is caused by bleeding, however. Certain foods, medications, supplements, and other substances can also make feces appear black.
Your dog’s overall condition and the persistence of the stool change are therefore important.
If your dog has genuinely black, sticky, tar-like stool, particularly if it happens repeatedly or occurs with vomiting, poor appetite, weakness, pale gums, abdominal pain, or dehydration, contact your veterinarian promptly.