Black Stool

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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.

Black stool that is tarry in texture and foul smelling is often a symptom of upper gastrointestinal bleeding from the esophagus, stomach or small intestine. This is called melena. Rectal bleeding of bright red blood with clots, sometimes mixed with stool, is called hematochezia. Hematochezia is often caused by bleeding from the lower digestive tract, including the colon, rectum or anus.

Very small amounts of blood in the stool may be seen by the naked eye and not significantly change the color of stool. This is called fecal occult blood, which can be a symptom of a serious disease and may be found with regular, routine medical testing.

Black stools can be a symptom of a serious condition, such as esophageal varices or peptic ulcer. Seek prompt medical care if you have unusually dark stools or any change in the color or texture of your stool. If your stools are black and tarry in texture, bloody, or if you have major rectal bleeding, seek immediate medical care (call 911).

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:

Serious symptoms that might indicate a life-threatening condition

In some cases, black stool can indicate 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 the following symptoms:

  • Change in level of consciousness or alertness, such as passing out or unresponsiveness

  • Change in mental status or sudden behavior change, such as confusion, delirium, lethargy, hallucinations and delusions

  • Dizziness

  • High fever (higher than 101 degrees Fahrenheit)

  • Palpitations

  • Rapid heart rate (tachycardia)

  • Respiratory or breathing problems, such as shortness of breath, difficulty breathing, labored breathing, wheezing, not breathing, or choking

  • Rigid, board-like abdomen

  • Severe abdominal pain

  • Severe diarrhea

  • Vomiting blood or black material (resembling coffee grounds)

  • Weakness (loss of strength)

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

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2020 Nov 2
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.
  1. Bloody or tarry stools. Medline Plus, a service of the National Library of Medicine National Institutes of Health.
  2. Bleeding esophageal varices. Medline Plus, a service of the National Library of Medicine National Institutes of Health.
  3. Gastrointestinal Bleeding. Medline Plus, a service of the National Library of Medicine National Institutes of Health.
  4. Lower Gastrointestinal Bleeding. Medscape.