Why Is My Poop Black? 7 Causes of Black or Tarry Stool
If you notice your poop is black or tarry, it might be due to something as simple as a change in your diet or a new medicine you're taking. Sometimes, though, it's a sign of a medical problem that you don't want to ignore.
Even if you think you know why it's happening, always call your doctor if you have black, tarry stools.
Iron Supplements
Black poop can be a side effect of iron pills you take for anemia -- a condition that happens when you don't have enough red blood cells to carry oxygen around your body.
Other side effects of iron supplements are:
- Stomachache
- Nausea
- Constipation
- Heartburn
Tell your doctor if you notice any problems after you take iron supplements. You may need to stop or switch to a different type.
Dark-Colored Foods
Sometimes dark-colored foods turn your poop black. These include:
- Black licorice
- Chocolate sandwich cookies
- Blueberries
- Grape juice
- Beets
The dark color should go away once you stop eating the food that caused it.
Medicines With Bismuth
Drugs for upset stomach like bismuth subsalicylate (Pepto-Bismol and Kaopectate) contain bismuth to calm your belly. Bismuth can turn your tongue and poop black.
This symptom is harmless. It should go away once you stop taking the medicine. Call your doctor and stop taking it if you:
- Have a ringing or buzzing sound in your ears or can't hear
- Feel worse after taking bismuth
Bleeding Ulcer
A bleeding ulcer is the most common concerning cause of dark stools. An ulcer is an open sore on the inside of your stomach or small intestine. Sometimes these sores bleed. This can make your poop dark. Blood exposed to gastric acids turns black and tarry (sticky). This is called melena and is a sign of an upper gastrointestinal bleed.
Alcohol and NSAIDs and hpylori increase your risk for gastric ulcers
Other signs that you have an ulcer include:
- Burning pain in your belly
- Swollen belly
- Burping
- Heartburn
- Nausea, throwing up, or having vomit that looks like coffee grounds
Some medicines for ulcers lower the amount of acid in your stomach. Others coat and protect it from the damage that stomach acids can cause.
Call your doctor if you:
- See blood in your poop or vomit
- Have trouble breathing
- Feel like you're about to pass out
- Have lost weight without trying
- Lose your appetite
Yesterday, my stool color was bright green. Should I be concerned?
Answer From Michael F. Picco, M.D.
Stool comes in a range of colors. All shades of brown and even green are considered normal. Only rarely does stool color indicate a potentially serious intestinal condition.
Stool color is generally influenced by what you eat as well as by the amount of bile — a yellow-green fluid that digests fats — in your stool. As bile pigments travel through your gastrointestinal tract, they are chemically altered by enzymes, changing the pigments from green to brown.
Consult your health care provider if you're concerned about your stool color. If your stool is bright red or black — which may indicate the presence of blood — seek prompt medical attention.
Stool quality What it may mean Possible dietary causes Green Food may be moving through the large intestine too quickly, such as due to diarrhea. As a result, bile doesn't have time to break down completely. Green leafy vegetables, green food coloring, such as in flavored drink mixes or ice pops, iron supplements. Light-colored, white or clay-colored A lack of bile in stool. This may indicate a bile duct obstruction. Certain medications, such as large doses of bismuth subsalicylate (Kaopectate, Pepto-Bismol) and other anti-diarrheal drugs. Yellow, greasy, foul-smelling Excess fat in the stool, such as due to a malabsorption disorder, for example, celiac disease. Sometimes the protein gluten, such as in breads and cereals. See a doctor for evaluation. Black Bleeding in the upper gastrointestinal tract, such as the stomach. Iron supplements, bismuth subsalicylate (Kaopectate, Pepto-Bismol), black licorice. Bright red Bleeding in the lower intestinal tract, such as the large intestine or rectum, often from hemorrhoids. Red food coloring, beets, cranberries, tomato juice or soup, red gelatin or drink mixes.There is a problem with information submitted for this request. Review/update the information highlighted below and resubmit the form.
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- Suneja M, et al., eds. The abdomen, perineum, anus, and rectosigmoid. In: DeGowin's Diagnostic Examination. 11th ed. McGraw Hill; 2020. https://accessmedicine.mhmedical.com. Accessed Sept. 28, 2020.
- Feldman M, et al., eds. Gastrointestinal bleeding. In: Sleisenger and Fordtran's Gastrointestinal and Liver Disease: Pathophysiology, Diagnosis, Management. 11th ed. Elsevier; 2021.https://www.clinicalkey.com. Accessed Sept. 28, 2020.
- What is celiac disease? Celiac Disease Foundation. https://celiac.org/about-celiac-disease/what-is-celiac-disease/. Accessed Sept. 28, 2020.
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