Black Stools: 10 Common Causes & What to Do

Updated in January 2024

Dark or black stool usually occurs when there is digested blood mixed in the feces. It is often a sign of bleeding at the beginning of the digestive tract, near the esophagus or stomach. Bleeding in these areas can happen due to ulcers or varices. 

Black poop can also happen with more minor coincidences, like with diets that are rich in iron or with people who take iron supplements. Some medication can also cause darker stools. 

Nonetheless, if your black stools persist for more than 2 days, you should see your doctor for assessment. A stool test will likely be ordered, and the doctor may also opt to send you for a colonoscopy. Once the underlying cause is identified, appropriate treatment can be initiated. Learn more about what different colors of poop can mean

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What causes black stools?

The most common causes of black stools are: 

1. High iron intake

Diets that are high in iron and contain plentiful amounts of beans, red meat or beets may result in darker stools. When foods with high iron contents are consumed, the intestine may not be able to absorb all the iron into the body, and eliminates excesses in the stool. Iron will often give the stool a black color. Check-out which iron-rich foods may be causing darker stools.

It is important to note, however, that dark stools from high iron will not have any changes to odor. Stools with blood, on the other hand, will have a more distinct smell. 

What to do: There is no need to consume an exaggerated amount of iron every day unless medically indicated. Reduce your iron intake and monitor your stool color, as it should return to its normal, lighter color within a few days. 

2. Intake of red or black foods

In addition to foods with high iron contents, foods with a very intense red or black color can also darken poop. Some examples include:

  • Licorice
  • Blackberries 
  • Dark chocolate
  • Jello with red food coloring
  • Beets

What to do: If you suspect that your stool color has changed due to your diet, monitor the types of food you eat and avoid very intensely-colored foods. If your black stools persist after a few days of monitoring, you should see your doctor for doctor. 

3. Medication or supplement use

Some supplements, like iron pills, can lead to black poop after their first days of use. Other medications that can cause black stools are anticoagulants and anti-inflammatories.

What to do: If you notice that your stool color has become darker within a few days of starting a new medication or supplement, you should advise your prescriber so that he or she can assess whether the medication is safe to continue.

4. Stomach ulcers

Stomach ulcers, also known as gastric ulcers, are lesions that form on the stomach lining. They can cause symptoms like stomach pain, vomiting and bleeding, which is then noted in the stools. Stools that contain blood will have an intensely foul odor and will be much darker than usual. Read more about what causes stomach ulcers and other symptoms you may experience.

What to do: Treatment for stomach ulcers is usually monitored by a gastroenterologist. Goals will be to treat the underlying cause, and may involve using medication to reduce or neutralize stomach acid. 

5. Esophageal varices

Esophageal varices occur when the blood vessels in the esophagus become dilated. This usually happens as a consequence of liver disease. Rupture of these vessels can lead to vomit with blood as well as blood in the feces, which gives stool a black color. You may also experience pallor, dizziness, and shortness of breath. 

What to do: Treatment for esophageal varices will depend on the severity, amount of bleeding and the underlying cause. Mild cases can be conservatively treated with medication, while more severe cases of vessel rupture will require surgical repair. 

6. Mallory-Weiss Syndrome

Mallory-Weiss syndrome is characterized by the presence of superficial lacerations in the esophageal lining. These small cuts can bleed and usually noted in the lower part of the esophagus, close to the junction with the stomach. This condition is associated with symptoms like vomit with blood and, in the more severe cases, dark stools, dizziness, fainting, and abdominal pain.

Mallory-Weiss syndrome is caused by excessive effort to vomit, retching or a strong blow to the abdomen. It is more common in people with a history of alcohol abuse, bulimia, gastroesophageal reflux or hyperemesis gravidarum.

What to do: It is important to follow treatment as prescribed. The doctor may prescribe IV fluids to replenish lost fluids, as well as stomach protectors to prevent stomach acidity from worsening the condition. Additionally, if  active bleeding is noted, the doctor may advise an endoscopy to localize the bleeding and prescribe more targeted treatement. In more serious cases, surgery may be required.

7. Esophagitis

Esophagitis is characterized by inflammation of the esophagus. It causes symptoms like heartburn, a bitter taste in the mouth, throat pain and, in the most serious cases, bleeding along the digestive tract that can make the stool black.

Also recommended: Erosive Esophagitis: Symptoms, Causes & Treatment

Esophagitis can occur due to infections, gastritis, use of medications and, mainly, GERD, which is when acidic stomach contents backflow into the esophagas, causing inflammation.

What to do: The doctor may also prescribe medications to reduce stomach acidity, such as omeprazole. A low fat diet with reduced intake of processed and spicy foods may also be beneficial. In more serious cases, the gastroenterologist may recommend surgery.

8. Duodenitis

Duodenitis is the inflammation of the tissue that covers the duodenum, which is the first portion of the small intestine. It can cause symptoms such as abdominal pain, nausea, vomiting, gas and, in some cases, bleeding along the digestive tract that causes black stools.

This condition is typically caused by the presence of H. pylori bacteria in the gastrointestinal tract or prolonged use of medications like ibuprofen or aspirin. It can also be a consequence of celiac disease, Crohn's disease, alcohol abuse, or cigarette consumption.

Also recommended: What Is Ibuprofen? 9 Uses, Side Effects & Contraindications

What to do: Treatment for duodenitis depends on the underlying cause. The doctor may prescribe medications to manage symptoms, like antibiotics and stomach protectors, as well as changes to diet and lifestyle habits.

9. Intestinal injury

Trauma or perforations along the gastrointestinal tract, like a gunshot or knife wound, for example, can also cause bleeding, and as a result, black stools.

What to do: Treatment depends on the degree of trauma and type of perforation. The gastroenterologist may advise surgery to repair the affected organ or tissue, and stop the bleeding.

10. Stomach or intestinal cancer

Stomach or intestinal cancer can also lead to dark stools due to increased sensitivity and risk for bleeding in these organs. 

What to do: Treatment for cancer, which is monitored by an oncologist, is aimed at destroying cancer cells and decreasing the risk for spreading. It may involve chemotherapy, radiation therapy and/or surgery. 

Black stools in babies

Black stools in babies are often observed in the first days after delivery. This first stool os called meconium, It is a dark green poop that is produced by the fetus while in-utero, and eliminated within the first hours of life. By the 6th day, the stool color may stool have some green or burgandy tinges. After a few weeks and months, baby stools will often change in color and textures. Poop will especially change with the introduction of new foods, like oatmeal, fruits, vegetables, meats and eggs. 

In some cases, baby stool may appear to have scant amounts of blood, however it is generally not a concern. It is usually a sign of a milk allergy or a cold virus. Nonetheless, you should still inform your doctor if you notice in red colors or new dark color changes in your baby’s stool. 

When to go to the doctor

You should see your doctor for assessment if you suspect that your stool contains blood. Other signs and symptoms that should be assessed include:

  • A new, intensely foul odor 
  • Severe abdominal pain 
  • Nausea and vomiting 
  • Bright red blood in the stool or vomit 
  • Weight loss 
  • Appetite changes 

The doctor will assess your symptoms and health history, and may order testing like a stool test or endoscopy.