A person’s poop may be black due to eating certain foods, such as licorice, taking iron supplements, or gastrointestinal bleeding. If people have blood in the stool, they may benefit from speaking with a doctor.

Various foods can turn a person’s stool black, including blueberries, licorice, and blood sausage. Certain medications, including iron tablets and the indigestion medication bismuth subsalicylate (Pepto-Bismol) may also turn stool black.

If someone has recently consumed any of these and their stool is black, there is likely no cause for concern.

However, bleeding in the gastrointestinal tract can also cause black, tarry stools. If this occurs, people may notice additional symptoms, including blood in the stool, abdominal cramps, and fatigue.

This article explains six potential causes for black stools, including how to prevent it and when to seek help.

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Angiodysplasia involves abnormal blood vessels in the mucous membrane of a person’s gastrointestinal tract.

It is unclear why angiodysplasia happens, but it can cause bleeding and blood in a person’s stool, which can make it look black and tarry.

Treatments may involve procedures such as argon plasma coagulation ablation or endoscopic clips and band ligation to stop the bleeding.

According to National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), people may have blood in the stool or black, tarry stools if they have benign tumors or cancerous formations in the following areas:

A benign tumor is a tumor that is not cancerous. Whether they are benign or cancerous, tumors can weaken the gastrointestinal wall and result in bleeding.

Tumors in the gastrointestinal tract may require surgery to remove them. If they are cancerous, treatment may depend on the type and extent of the cancer, as well as the person’s general health.

Ulcerative colitis is an inflammatory condition that causes ulcers to form within the large intestine. This can cause blood in a person’s stool, which may make the stool appear black and tarry.

Other symptoms may include:

The cause of ulcerative colitis is unclear but genetics may play a role. Doctors can treat the condition with medications and surgery.

Polyps are small growths that form in the large intestine. They are not necessarily cancerous, but they can become cancerous over time.

Colon polyps can cause blood in the stool, giving it a black, tarry appearance. However, they typically need to be very large to cause bleeding.

A doctor may suggest surgery to remove the colon polyps.

Issues with the esophagus may cause bleeding, which can turn a person’s stool black and tarry. The NIDDK suggests that these problems can include esophageal varices and gastroesophageal reflux.

Liver issues can cause esophageal varices, which are enlarged veins in the esophagus. Treatment will focus on stopping the bleeding and resolving the underlying cause.

If someone experiences gastroesophageal reflux frequently, they may have gastroesophageal reflux disease (GERD).

The main causes are complications from certain medications, smoking, or increased pressure in the abdomen. This pressure can result, for example, from obesity or pregnancy.

People can typically manage GERD with lifestyle changes, such as avoiding certain foods and maintaining a moderate weight. A doctor may also recommend medications, such as antacids.

If an ulcer forms in a person’s stomach, this can cause bleeding which may make the stool black and tarry.

The NIDDK notes that the long-term use of some drugs, such as ibuprofen (Advil) and aspirin, can cause stomach ulcers. A bacterial infection can also be a cause.

As well as blood in a person’s stool, symptoms include:

If a doctor thinks that medications are causing stomach ulcers, treatment may involve stopping the use of these pain relievers. A doctor may prescribe other medications to treat alternative causes, such as bacterial infections.

If a person’s stool is black because of what they have eaten, the color will eventually change with the diet. However, there is no reason for people to avoid foods that have this effect if they are not experiencing any other symptoms.

If bleeding in the gastrointestinal tract is responsible for black, tarry stools, a doctor will need to diagnose the exact cause of this. Many gastrointestinal issues are treatable.

Signs that someone should speak with a doctor include abdominal pain, dizziness, and fatigue. People may require urgent medical help if they experience any of the following:

Doctors can diagnose the underlying cause of gastrointestinal bleeding and provide suitable treatment, which should return a person’s stool to their usual color.

People may be able to prevent black stools by avoiding certain foods, such as black licorice and blood sausage.

It may not be possible to entirely prevent all potential causes of gastrointestinal bleeding that can lead to black stools. However, a healthcare professional may recommend the following lifestyle changes to lower the risk:

People can speak with a doctor if they have concerns about their risk of gastrointestinal bleeding.

If a person’s stool is black, the likeliest reasons is that they have eaten certain foods. Some people may have black stools due to gastrointestinal bleeding.

If someone has no other symptoms and suspects that foods are to blame, there should be no cause for concern. However, if they notice blood in their stool or experience any other symptoms, they should speak with a doctor, who can determine the cause.

Treatment may depend on the underlying cause of gastrointestinal bleeding.