Black stool can be with or without visible blood. It may be as a result of various causes, including eating dark-colored foods, gastrointestinal bleeding, and taking certain medications.
Although it is not always a sign of a bigger problem, tell your doctor any time you have black, tarry stools to rule out any serious medical conditions.
So if you are looking to know what black stool mean, whether having black poop is bad, foods that can turn your stool black and more about how long black stool should last once you start seeing it then this guide is right for you.
What Causes Black, Tarry Stools?
Most cases of black stools can be traced back to a food you ate, specifically dark-colored foods such as:
- Black licorice
- Dark chocolate cookies
- Grape juice
- Blood sausage
If you have recently consumed any of these and you notice your stool is black, there is likely no cause of concern. The dark color should go away once you stop eating the food responsible. Foods that are colored and range from dark blue, black, or dark green could produce black stool.
If you don’t have enough iron due to any number of reasons, your body can’t produce enough hemoglobin, the substance in red blood cells that carries oxygen from your lungs to your body’s organs and tissues.
This results in a condition known as iron deficiency anemia, which is corrected by taking iron supplements. Among the side effects of iron supplements are constipation and black stools. Constipation can cause black stool.
The black stool produced by iron supplements should only be black and should not appear tarry or contain traces of blood. Your poop will remain black for as long as you use iron supplements. Eating foods naturally high in iron, such as dark leafy greens, red meats, and fish, does not cause your stool to darken.
Note: Tell your doctor if you notice any problems after you take iron supplements. You may need to stop or switch to a different type.
Bismuth containing drugs
Bismuth is a chemical element used in drugs, such as:
- Valproate bismuth. A medication used to treat laryngitis.
- Bismuth subsalicylate (Pepto-Bismol and Kaopectate). A medication used to treat nausea, heartburn, indigestion, upset stomach, and other temporary discomforts of the stomach and gastrointestinal tract.
- Bismuth subgallate. A medication used to deodorize flatulence and stools.
- Bismuth subnitrate. A medication used as an antacid.
Bismuth can turn your tongue and stool black, which is harmless. The blackened stool should go away once you stop taking the medication containing bismuth, but it can continue for up to several days after.
Peptic ulcers are open sores that develop on the inside lining of your stomach and the upper portion of your small intestine.
Sometimes these sores bleed, causing dark blood in stools or stools that are black or tarry. Treating the ulcer can stop the bleeding and prevent black stool.
See your doctor if your poop is black or there’s blood in your poop and if you have other severe signs or symptoms of ulcers, including:
- Vomiting or blood in vomit, which may appear red or black
- Trouble breathing
- Feeling like you’re about to faint
- Loss of appetite
- Unexplained weight loss
Issues with your esophagus may cause bleeding, which can turn your stool black and tarry. These problems include:
- Esophageal varices: Enlarged or swollen veins in the esophagus that are common in people with liver problems. These veins can sometimes leak blood or suddenly rupture, causing black stools when you swallow and digest the blood. Treatment of esophageal varices focuses on stopping the bleeding and resolving the underlying condition.
- Esophageal cancer: Cancer of the esophagus is marked by chest pain, difficulty swallowing, unintentional weight loss, worsening indigestion or heartburn, coughing, and dark stool from digested blood. Treatment focuses on removing cancer through surgery, chemotherapy, or radiation.
- Mallory-Weiss tear: A tear of the tissue of your lower esophagus. It is characterized by upper gastrointestinal bleeding, which can lead to the formation of black stool that contains dark, tar-like blood. The tear is most often caused by violent coughing or vomiting and usually heals on its own. However, severe cases may require surgery or other interventions.
Early and advanced stomach cancer can bleed into the stomach, causing blood in your stools or black stools.
Other symptoms of stomach cancer include feeling bloated after eating, indigestion or heartburn, nausea or vomiting, feeling full after eating small amounts of food, loss of appetite, fatigue, and unexplained weight loss.
Stomach cancer treatment options may include surgery, radiation therapy, chemotherapy, targeted therapy, or immunotherapy. Often, a combination of treatments is used.
Other possible health conditions that can cause black stool, include:
- Colon cancer: Cancer of the rectum or colon marked by abdominal pain or discomfort, changes in bowel habits, and blood in stools (either bright red spots or dark tar-like stools).
- Colorectal polyps: Small growths on the lining of the rectum or colon that can cause black stools if bleeding heavily.
- Colitis: An inflammatory reaction in the colon marked by symptoms of diarrhea, abdominal pain, and black stool.
- Crohn’s disease: A chronic inflammatory bowel disease that affects the lining of the digestive tract, causing abdominal pain, diarrhea, nausea, fatigue, loss of appetite, and rectal bleeding.
Related: A guide on What to Eat for Diarrhea
Diagnosing Black Stool
After knowing what black stool mean, now let’s know how you can get diagnosed and receive black stool treatment. Your doctor will ask you several questions to determine the cause of your black stool color. These questions may include:
- How long have you had black stools?
- Have you had any rectal bleeding, bloody stools, or vomiting of blood?
- What medications, vitamins, and supplements, if any, are you taking?
- Do you have any other symptoms?
To check for blood in the stool, your doctor will perform a rectal examination or obtain a stool sample. After melena is confirmed, a physician may order other diagnostic tests to determine the cause and the exact location of the bleeding.
An esophagogastroduodenoscopy (EGD) is usually the definitive test in determining the cause of the bleeding. However, other tests may be required if the EGD proves inconclusive. These tests may include blood tests, CT scans, X-rays, gastroscopy, colonoscopy, and capsule endoscopy.
Treatment for Black Stools
Treatment options for black stool depend on the underlying cause.
For instance, people with cancer who have hemorrhoids can ease the passage of stool and reduce bleeding by using stool softeners as directed.
In the case of bleeding ulcers, your doctor may prescribe acid-reducing medications. If H. pylori is found in your digestive tract, your doctor may also prescribe antibiotic medications to kill the bacterium.
Vein abnormalities and blockages may require surgical repair if the bleeding doesn’t stop on its own.
How to Prevent Black Stool
Based on the diagnosis, your doctor will advise you on the best way to prevent further bleeding in the gastrointestinal tract, which may include lifestyle changes.
Drinking plenty of water and eating lots of fiber, for instance, can help lessen the occurrence of black stools as they help soften stool, easing its passage from your body.
However, consult your doctor before starting on a high-fiber diet as it could do more harm than good depending on your underlying condition. Some people with inflammatory bowel disease find that high-fiber foods trigger flares, which worsens the disease.
Healthtuition has strict sourcing guidelines. We rely on academic research institutions, peer-reviewed studies, and medical associations. We avoid using tertiary references. Learn more about how we ensure our content is accurate and current by reading our editorial policy.
- Healthline (July 31, 2019). Why Are My Stools Black?. healthline.com/health/bloody-or-tarry-stools
- Verywellhealth (June 29, 2020). What Are the Causes of Black Stool? verywellhealth.com/causes-of-black-stool-1941711
- Healthgrades Editorial Staff (October 19, 2018). Black Stool. healthgrades.com/right-care/digestive-health/black-stool
- National Library of Medicine (n.d). Gastrointestinal Bleeding. medlineplus.gov/gastrointestinalbleeding.html