What causes black stool?

Black stool can be a symptom of a variety of diseases, disorders or conditions, including infection, inflammation, trauma and malignancy. Common causes include stomach ulcer (peptic ulcer) and inflammation of the gastrointestinal tract from the use of nonsteroidal anti-inflammatory drugs (NSAIDs, such as ibuprofen and aspirin).

Stools that are black and tarry in texture are often caused by bleeding from the upper gastrointestinal tract (esophagus, stomach, or small intestine). Bleeding from the rectum and red or maroon-colored stools often originate from bleeding in the lower gastrointestinal tract (colon, rectum or anus). Both conditions may occur together.

Conditions of the gastrointestinal tract that cause black stool

Black stool can be due to a variety of serious or life-threatening conditions that result in bleeding of the gastrointestinal tract including:

  • Abdominal or esophageal trauma

  • Abnormal blood vessel

  • Bleeding esophageal varices (abnormally widened or distended blood vessels in the esophagus that rupture)

  • Bleeding peptic ulcer (stomach or small intestine ulcer)

  • Bowel ischemia (lack of normal blood flow to the intestines and death of intestinal tissue)

  • Gastritis, such as irritation and swelling of the stomach caused by nonsteroidal anti-inflammatory drugs (NSAIDs)

  • Inflammatory bowel disease (includes Crohn’s disease and ulcerative colitis)

  • Radiation therapy

  • Stomach cancer or other types of upper gastrointestinal cancer

Medications and foods that cause black stool

Black stool can be caused by medications and other ingested substances including:

  • Bismuth-containing medications, such as Pepto Bismol or Kaopectate

  • Black licorice

  • Iron supplements

Questions for diagnosing the cause of black stool

To diagnose the underlying cause of black stool, your doctor or licensed health care practitioner will ask you questions about your symptoms. You can best help your health care practitioner in diagnosing the cause of black stool by providing complete answers to these questions:

  • How long have you had black stools?

  • Have you had any rectal bleeding, bloody stools, or vomiting of blood?

  • What medications, vitamins, and herbal supplements are you taking?

  • Do you have any other symptoms?

What are the potential complications of black stool?

Black stool can be caused by a serious or life-threatening disease or condition of the gastrointestinal tract, such as a bleeding ulcer. It is important to contact your health care provider if you develop black stools, bloody stools, rectal bleeding, or a color change in your stools. You can best reduce the risk of complications of black stool and its underlying causes by following the treatment plan you and your health care provider design specifically for you. Failure to seek prompt diagnosis and treatment for black stool can result in life-threatening complications, such as:

  • Anemia

  • Hemorrhage and severe blood loss

  • Shock

  • Spread of cancer and terminal cancer


  1. Bloody or tarry stools. Medline Plus, a service of the National Library of Medicine National Institutes of Health. www.nlm.nih.gov/medlineplus/ency/article/003130.htm.
  2. Bleeding esophageal varices. Medline Plus, a service of the National Library of Medicine National Institutes of Health. www.nlm.nih.gov/medlineplus/ency/article/000268.htm.
  3. Gastrointestinal Bleeding. Medline Plus, a service of the National Library of Medicine National Institutes of Health. www.nlm.nih.gov/medlineplus/gastrointestinalbleeding.html.
  4. Lower Gastrointestinal Bleeding. Medscape. http://emedicine.medscape.com/article/188478-overview.

What is black stool?

Black stool is a condition in which the feces are very dark or black in color. Black stool may be normal in some cases and caused by ingesting certain substances or medications, such as iron supplements. However, black stool can also be caused by a serious condition, such as bleeding in the digestive tract caused by a peptic ulcer.

... Read more about black stoolintroduction


What other symptoms might occur with black stool?

Black stool may be accompanied by other symptoms, which vary depending on the underlying disease, disorder or condition. Symptoms that may accompany black stool include:

  • Abdominal pain or cramping

  • Abdominal swelling or bloated feeling

  • Read more about black stoolsymptoms

Medical Reviewer: Cynthia Haines, MD Last Annual Review Date: Jul 30, 2013 Copyright: © Copyright 2014 Health Grades, Inc. All rights reserved. May not be reproduced or reprinted without permission from Health Grades, Inc. Use of this information is governed by the HealthGrades User Agreement.

This Article is Filed Under: Digestive System

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