Stool Color

Medically Reviewed By William C. Lloyd III, MD, FACS
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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 to bleeding in the digestive tract.

The color of bloody stool depends on the site of the bleeding and how quickly food moves through the digestive system. Blood from the esophagus, stomach, and small intestine may have time to be digested, resulting in dark, tarry stool. Red blood in the stool frequently comes from the lower portion of the digestive tract, specifically the colon or anus. However, bleeding from a higher portion of the digestive tract can speed digestive transit, also leading to red stool. Red striping of the stool is often related to bleeding of the rectum or anus and may be seen in stool of people who have hemorrhoids (inflamed veins in lower rectum or anus).

Pale stool can occur if bile salt production is reduced or its transport is blocked due to serious liver infections or a bile duct obstruction that is caused by stones, scarring, abnormal development, or external compression. Liver disease and bile duct obstruction can also cause jaundice, a yellowing of the skin and whites of the eyes that may be accompanied by itching.

Changes in stool color can be related to diet, supplements or medications; however, stool that is persistently dark or light can be an indication of a serious medical problem. Seek immediate medical care (call 911) for bloody stool, which may be red or black or tarry in consistency, and may be accompanied by severe pain, profuse sweating, alterations in level of consciousness, rapid heartbeat (tachycardia), vomiting blood, or chest pain.

If your stool color changes are persistent or cause you concern, seek prompt medical care.

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 digestive tract including:

  • Abdominal pain or cramping
  • Abdominal swelling, distension or bloating
  • Changes in bowel movements
  • Diarrhea
  • Fecal incontinence (inability to control stools)
  • Indigestion
  • Nausea with or without vomiting
  • Painful bowel movements
  • Urgent need to pass stool

Other symptoms that may occur along with stool color changes

Stool color changes may accompany symptoms related to other body systems including:

Serious symptoms that might indicate a life-threatening condition

In some cases, changes of stool color may be a symptom of a life-threatening condition that should be immediately evaluated in an emergency setting. Seek immediate medical care (call 911) if you, or someone you are with, have any of these life-threatening symptoms including:

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:

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

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2021 Jan 10
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THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
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  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
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