What Does Dark Stool Mean?

A dark stool refers to a stool that is either black or dark red in color. You may pass dark bowel movements after consuming dark-colored foods or when an injury or bleeding is present in your gastrointestinal tract. If you pass dark or bloody stools, see your doctor immediately to rule out serious health conditions. 

For some people, passing dark stools are expected, especially those who have had a colectomy or ostomy surgery (bowel diversion). Other reasons could be the use of iron supplements.

Black Stools

Black, tarry stools may indicate bleeding in the upper digestive tract, which includes the upper portion of the small intestine, stomach, and the esophagus. Bleeding occurs when ulcers are present or when there is esophageal irritation or gastritis. When blood combines with digestive fluids, its appearance becomes black like tar. 

• Ulcer: Black stools can be due to a bleeding stomach ulcer. Although eating spicy food and stress can aggravate existing ulcers, they are not the main cause of stomach ulcers. Infection with the bacterium called Helicobacter pylori (H. pylori) is usually the cause. To treat this bacterial infection, antibiotics are usually prescribed along with an acid reducer. 

• Nonsteroidal Anti-Inflammatory Drugs (NSAIDs): NSAIDs tend to irritate and weaken the stomach lining's ability to withstand the acid in the stomach. For this reason, chronic use of NSAIDs can contribute to the development of stomach ulcers. These medications also have an adverse effect on people who have ulcerative colitis and Crohn's disease. NSAIDs are available over-the-counter but can also be prescribed by healthcare providers. Common over-the-counter NSAIDs include aspirin, ibuprofen, and naproxen sodium. Discontinuing the NSAID causing the stomach ulcers often fixes the problem. 

• Esophageal Varices: These are dilated veins in the upper stomach and wall of the lower esophagus. When these veins burst, bleeding and other serious complications may occur. 

• Gastritis: This condition is caused by stomach lining irritation or inflammation. Inflammation of the stomach lining can be due to smoking, bacterial infection, excessive alcohol intake, consumption of spicy foods, or chronic NSAID use. It can also develop after surgery or may be linked to an already existing health condition. 

• Mallory-Weiss Syndrome: This condition is characterized by a tear in the mucous membrane, where the stomach and esophagus meets. Black stools are passed when this tear bleeds.  

• Medications: Black-colored stools can also be due to certain medications, such as bismuth-based drugs and iron supplements.

In some cases, abnormalities in the circulatory system can also cause black bowel movements. They include:

• Bleeding gastric varices 
• Vascular malformations
• Bowel or intestinal ischemia 

Black stools may also be caused by the intake of foods that are green, black, or dark blue in color. Below is a list of substances that can cause dark stools:

• Iron supplements
• Lead
• Blueberries
• Bismuth (Pepto-Bismol)
• Black licorice
• Beets
• Red gelatin
• Colored fruit punch

Passing black stools is probably fine, especially if you can identify which foods may have caused your stools to become dark in color. However, if you pass black stools without taking iron supplements, dark foods, or Pepto-Bismol, see your doctor immediately. 

Red or Bloody Stools

Passing red, bloody stools can have several causes, which include lower digestive tract bleeding, hemorrhoids, inflammatory bowel diseases, colorectal polyps, and cancer. 

The inflammatory bowel diseases that can cause maroon or bright red blood in the stool include ulcerative colitis, Crohn's disease, and diverticulosis. Bloody stools are also commonly caused by hemorrhoids, which are swollen veins in your anus or rectum that can bleed during bowel movements. 

Diagnosing Dark Stools

To determine the cause of dark stools, your healthcare provider will take your medical history. A physical examination will be performed afterward. 

The doctor will probably ask for a stool sample and order blood tests. To check how blood flows in your digestive system, imaging tests, such as X-rays, CT scans, and MRIs can be used. These tests can help reveal blockages that could be the cause of bleeding in your gastrointestinal (GI) tract. 

A colonoscopy may also be performed to assess the health of your colon. This procedure involves the use of a long, flexible tube with a camera and light source at its tip. 

Treatment Options

Treatment of black or bloody stools usually depends on their cause. Stool softeners, under the instruction of a doctor, can be used by people who have cancer and hemorrhoids to help reduce bleeding during bowel movements, according to the American Cancer Society. Bleeding and pain from hemorrhoids can also be relieved through sitz baths. 

For bleeding ulcers, healthcare providers may prescribe acid-reducing drugs for treatment. When it comes to infections and inflammatory bowel diseases, antibiotics and immunosuppressant medications can be used. 

A surgical repair may be necessary, especially if bleeding from blockages and vein abnormalities does not stop. People have an increased risk of developing anemia if they have lost a lot of blood through their bowel movements. To help replace lost red blood cells (RBCs), a blood transfusion may be required. 

In some people, passing bloody stools due to colorectal polyps can indicate cancer or precancerous conditions. If cancer is present, chemotherapy and radiation therapy may be required. In other cases, polyp removal can solve the problem. 

Prevention

Consuming lots of fiber-rich foods and drinking plenty of water can help reduce the occurrence of dark-colored stools. Bowel movements can be easier when fiber and water are taken since they help soften the stool. The following high-fiber foods can be consumed to help improve bowel movements:

• Whole grains
• Beans
• Artichokes
• Pears
• Raspberries

If you decide on taking a high-fiber diet, make sure to let your healthcare provider know beforehand. Eating berries can cause irritation, especially in people who have inflammatory gastric conditions. 

When to See a Doctor

Seek immediate medical help if black stools are accompanied by the following symptoms:

• Vomiting blood or having dark-brown or black coffee grounds in your vomit
• Feeling faint
• Fainting
• Dizziness
• Pain

These signs and symptoms are known risk factors of digestive tract bleeding. Talk to your healthcare provider regarding the presence of blood in stool and the potential for bleeding, especially if you have any of the following risk factors:

• Peptic ulcer
• Cancer
• Liver disease
• Mallory-Weiss syndrome
• Intestinal ischemia 
• Gastric varices
• Dieulafoy lesions
• Erosive gastritis
• Erosive esophagitis