What causes stool color?

Stool color is due to digestion of bile salts produced in the liver and can be influenced by diet, medications or supplements. Bleeding in the digestive tract can cause red, dark or black stool. Liver problems and conditions causing obstruction of the bile ducts can cause pale stools.

Foods, medications, and supplement causes of stool color changes

Dark brown, bluish, reddish, or black stool color may be caused by foods, medications, and supplements including:

  • Beets
  • Black licorice
  • Blueberries
  • Iron supplements
  • Medications containing bismuth subsalicylate (Kaopectate, Pepto-Bismol)

Bile salt-related causes of stool color changes

The reduction or absence of bile salts, which are produced by the liver and stored in the gallbladder, can cause pale stool. Causes of pale colored stool include:

  • Biliary atresia (a condition present at birth involving abnormal bile duct development)
  • Biliary cirrhosis (inflammation of bile ducts in the liver)
  • Biliary stricture (narrowing of the common bile duct, the tube that carries bile from the liver and gallbladder to the intestines)
  • Cancer or tumors of the liver, the bile ducts, gallbladder, or pancreas
  • Gallstones
  • Hepatitis (liver infection or inflammation)
  • Sclerosing cholangitis (bile duct inflammation and scarring)

Digestive tract bleeding causes of stool color changes

Red or black stool can result from digestive tract bleeding, which may be due to conditions including:

  • Anal fissures (tears or cracks in anal tissue)
  • Atrophic gastritis (inflammation and thinning of the stomach lining)
  • Bacterial, parasitic or viral infection of the gastrointestinal tract
  • Cancer of the digestive tract
  • Celiac disease (severe sensitivity to gluten from wheat and other grains that causes intestinal damage)
  • Diverticulitis (inflammation of an abnormal pocket in the colon)
  • Gastroesophageal reflux disease (GERD)
  • Hemorrhoids (inflamed veins in the lower rectum or anus)
  • Inflammatory bowel disease (includes Crohn’s disease and ulcerative colitis)
  • Polyps in the colon (small growths inside the colon)
  • Ulcers of the stomach or duodenum

Serious or life-threatening causes of stool color changes

In some cases, stool color changes may be a symptom of a serious or life-threatening condition that should be immediately evaluated in an emergency setting. These include:

  • Abdominal trauma
  • Bleeding esophageal varices (life-threatening rupture and hemorrhage of swollen veins in the esophagus)
  • Blood vessel malformations
  • Colonic volvulus (twisting of the colon)
  • Intestinal ischemia (loss of blood supply to the intestines leading to death of intestinal tissue)
  • Intussusception (telescoping of the intestines into themselves)
  • Mallory-Weiss tear (tear of the lining of the esophagus from severe vomiting or coughing)
  • Perforated diverticulum (rupture of an abnormal pocket in the colon)
  • Perforated peptic ulcer (bleeding stomach or intestinal ulcer)

Questions for diagnosing the cause of stool color changes

To diagnose your condition, your doctor or licensed health care practitioner will ask you several questions related to your stool color including:

  • When did you first notice a change in your stool color?
  • How would you describe your stool?
  • What have you been eating recently?
  • Have you had any abdominal trauma or swallowed any objects?
  • Do you have any other symptoms?
  • What medications and supplements are you taking?

What are the potential complications of stool color?

Because changes of stool color can be due to serious diseases, failure to seek treatment can result in serious complications and permanent damage. Once the underlying cause is diagnosed, it is important for you to follow the treatment plan that you and your health care professional design specifically for you to reduce the risk of potential complications including:

  • Anemia (low red blood cell count)
  • Hemorrhage
  • Intestinal obstruction and rupture of the intestinal wall
  • Poor nutrition due to diarrhea or a decreased desire to eat
  • Spread of cancer
  • Spread of infection
  • Surgery to remove parts of the digestive tract due to serious infection or malignant condition


  1. Stools - pale or clay-colored. MedlinePlus, a service of the National Library of Medicine National Institutes of Health. http://www.nlm.nih.gov/medlineplus/ency/article/003129.htm.
  2. Bloody or tarry stools. MedlinePlus, a service of the National Library of Medicine National Institutes of Health. http://www.nlm.nih.gov/medlineplus/ency/article/003130.htm
  3. Collins RD. Differential Diagnosis in Primary Care, 5th ed. Philadelphia: Lippincott, Williams & Williams, 2012.
  4. Kahan S, Miller R, Smith EG (Eds.). In A Page Signs & Symptoms, 2d ed. Philadelphia: Lippincott, Williams & Williams, 2009.

What is stool color?

Stool is naturally brown due to the digestion of bile salts produced by the liver and blood pigments such as bilirubin. Dietary supplements including iron, medications, and some foods, such as blueberries, beets, or black licorice, can darken the stool or even turn it black. Dark stool, when not associated with diet, supplements or medications, can be a worrisome symptom, as it can be due ... Read more about stool colorintroduction


What other symptoms might occur with stool color?

Changes in stool color are generally related to the digestive tract, whether caused by food, supplements or medications, or due to something more serious such as digestive tract bleeding, liver problems, or obstruction of the bile ducts.

Digestive symptoms that may occur along with stool color changes

Stool color changes may accompany other symptoms affecting the digest... Read more about stool colorsymptoms

Medical Reviewer: William C. Lloyd III, MD, FACS Last Annual Review Date: May 7, 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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