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Black Stool

Symptoms, Causes, Questions & Related Topics

Top 8 Black Stool Causes

1. Bleeding Ulcer

A bleeding ulcer happens when the digestive tract contains too much acid or too little mucus, and the acid erodes the lining of the stomach or small intestine to cause an open sore. The blood released by an ulcer can mix with regular stool to cause blackened stool that has a sticky consistency.[1] Treating the ulcer can stop the bleeding and prevent black stool.

2. Dark-Colored Foods

Foods that are naturally dark-colored or darkened with food coloring can cause black stool: blueberries, blood sausage, dark chocolate, and black licorice.[2] Evaluating the diet and eliminating black-colored foods can help determine whether these black foods have caused black stool. Any food that is black, dark blue, or dark green could produce black stool.

3. Gastritis

Gastritis is inflammation in the lining of the stomach. Gastritis can be caused by stress, chronic vomiting, excessive alcohol intake, and the use of medications, such as aspirin and anti-inflammatory drugs.[3] Bacterial and viral infections, bile reflux, and bacteria called Helicobacter pylori are other common causes of gastritis.

Symptoms of gastritis include nausea, vomiting, abdominal pain and bloating, and black, tarry stool. Treatment for gastritis might include avoiding foods such as dairy and alcohol, which drive inflammation, or using medications that reduce or neutralize stomach acid.[4]

4. Esophageal Varices

Esophageal varices are enlarged or swollen veins on the lining of the esophagus. These veins might slowly leak blood or suddenly rupture to cause severe and life-threatening bleeding. With severe cases of bleeding from esophageal varices, a person can vomit large amounts of blood.[5] Those who experience less severe bleeding from this condition could swallow and digest the blood, causing black stool.

Esophageal varices can be the result of blood clots, parasitic infection, cirrhosis of the liver, and any other type of serious liver disease. People with this condition can prevent instances of bleeding by using medications that lower blood pressure, avoiding alcohol, and eating healthy whole foods, including fruits, vegetables, lean proteins, and whole grains.[6]

5. Mallory-Weiss Tear

A Mallory-Weiss tear, also known as Mallory-Weiss syndrome, is a tear in the mucous membrane at the point where the esophagus meets the stomach. These tears can cause severe bleeding and lead to the formation of black stool that contains dark, tarlike blood.[7]

A Mallory-Weiss tear is most commonly caused by prolonged or severe vomiting, such as that associated with bulimia or alcohol abuse. This tear can also be a result of heavy lifting or straining, trauma to the chest or abdomen, intense coughing, or gastritis. Bleeding caused by the Mallory-Weiss tear usually heals on its own within a few days without treatment, but it could require surgery or other interventions in severe cases.[7]

6. Iron Supplements

Nutritional iron supplements can turn stool black; in this case, the black stool is a sign that the body is fully absorbing the iron supplement.[8] The black stool produced by iron supplements should only be black in color and should not look tarry or contain streaks of blood. Eating foods naturally high in iron, such as dark leafy greens, red meats, and fish, does not cause darkened stool. Stool will remain black for as long as the person uses iron supplements.

7. Trauma or Foreign Object

Trauma to the abdomen or rectum can cause bleeding that results in black stool. Examples of trauma that could cause black stool include severe blows from auto accidents, knife or gunshot wounds, and appendicitis.[9] Damage caused by swallowing a caustic substance or foreign object can also tear the stomach, intestine, or rectum to cause bleeding and black stool. Treating the affected area and allowing for healing to occur can help eliminate black stool.

8. Medications Containing Bismuth

Bismuth is a chemical element commonly used in medications that treat nausea, heartburn, and upset stomach. Bismuth combines with small amounts of sulfur in saliva and the gastrointestinal tract to form a black substance called bismuth sulfide.[10] This substance can lead to blackened stool and tongue. Pepto-Bismol and Kaopectate are two widely used medications that contain bismuth and can cause black stool. Blackened stool can occur for up to several days after stopping the use of bismuth-containing products.

Possible Health Conditions Related to Black Stool

  • Bleeding esophageal varices: Swollen or enlarged veins in the esophagus that leak blood or suddenly rupture.
  • Bleeding ulcer: A tear in the stomach lining or intestine caused by high amounts of stomach acid and characterized by symptoms of nausea, vomiting, and unexplained weight loss.
  • Colon cancer: Cancer of the rectum or colon marked by symptoms of abdominal pain or discomfort, changes in bowel habits, and blackened stool.
  • Colorectal polyps: Small growths on the lining of the rectum or colon that can cause rectal bleeding or black stool.
  • Colitis: An inflammatory reaction in the colon marked by symptoms of diarrhea, abdominal pain, and black stool.
  • Crohn’s disease: A chronic inflammatory condition of the gastrointestinal tract characterized by nausea, vomiting, and rectal bleeding.
  • Enteritis: Inflammation of the small intestine that produces symptoms of abdominal cramps, diarrhea, and black stool.
  • Esophageal cancer: Cancer of the esophagus marked by symptoms of chest pain, difficulty swallowing, and dark stool from digested blood.

Questions Your Doctor May Ask About Black Stool

  • How long have you been experiencing black stool?
  • How often do you experience black stool?
  • Do you notice certain foods are contributing to black stool?
  • Have you recently lost weight?
  • Is there any blood on the toilet paper?
  • Have you recently experienced trauma?
  • Have you accidentally swallowed a foreign object?
  • What medicines and medications do you use?
  • What other symptoms do you experience?

Black Stool May Also be Known as

  • Black poop
  • Dark poop
  • Dark stool
  • Darkened stool
  • Blackened stool
  • Tarry stool
  • Tarry poop
  • Bloody stool
  • Bloody poop
  • Melena


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