Black stools can indicate bleeding or other injuries in your gastrointestinal tract. You may also have dark, discolored bowel movements after eating dark-colored foods. Tell your doctor any time you have bloody or black-colored stool to rule out serious medical conditions.
Black, tarry stools
Bleeding in the upper portion of your digestive system can cause black, tarry stools. Ulcers or another form of irritation in your esophagus or stomach known as gastritis can cause bleeding. When the blood mixes with digestive fluids, it takes on the appearance of tar.
Certain medications can also lead to black-colored stools. Iron supplements and bismuth-based medications, for example, can darken your stools.
Sometimes, serious blood and circulation abnormalities in your digestive system can cause black, tarry stools. These can include the following:
- bowel ischemia: a reduction of blood flow to the intestines
- vascular malformation: misshapen veins
- varices: large, protruding veins in the intestines
Red, bloody stools
Red or bloody stools can also be due to several different medical conditions. Your stools may be bloody due to bleeding in the lower half of your digestive system.
Cancerous or benign polyps on your colon can produce gastrointestinal bleeding in some cases. Inflammatory bowel disease (IBD) is the name of a group of intestinal diseases that cause prolonged inflammation. Examples include:
IBD may cause you to release bright red or maroon-colored blood in your stool.
A common cause of bloody stools is the presence of hemorrhoids. Hemorrhoids are swollen veins located in your rectum or anus. Straining to produce a bowel movement can cause bleeding.
Blockages at any point in your digestive tract can cause black, tarry, or bloody stools.
The foods you eat can cause your stools to appear bloody or tarry. Eating red or black foods can give your feces a dark appearance without the existence of blood.
The following foods can discolor your bowel movements:
- black licorice
- dark chocolate cookies
- red-colored gelatin
- red fruit punch
Your doctor will request your medical history and perform a physical examination to determine the cause of your unusual stool color. They’ll probably order blood tests and a stool sample.
Imaging tests such as MRIs, X-rays, and CT scans can help them see the blood flow to your digestive system. These diagnostic tools will reveal any blockages that could be causing gastrointestinal bleeding.
A colonoscopy is often performed while you’re under sedation. Your doctor will use a thin, flexible tube with a camera on the end to see the inside of your colon and look for the cause of your symptoms.
Treating black stools varies according what’s causing the condition.
According to the American Cancer Society, people with cancer who have hemorrhoids can ease the passage of stool and reduce bleeding by using stool softeners under a doctor’s direction. Sitz baths can also ease pain from hemorrhoids and prevent bleeding.
Your doctor may prescribe acid-reducing medications to treat bleeding ulcers. Antibiotics and immunosuppressant drugs can also calm IBD and infections.
Vein abnormalities and blockages may require surgical repair if the bleeding doesn’t stop on its own. If you’ve lost a lot of blood through your stool, you may be at risk of developing anemia. You may need a blood transfusion to replenish your supply of red blood cells.
Polyps on your colon that cause bloody stools can indicate precancerous conditions or cancer in some people. Your doctor will determine the appropriate treatment for these conditions. Removal of the polyps may be all that’s necessary in some cases. Other polyps may require radiation therapy and chemotherapy if cancer is present.
You can help lessen the occurrence of black stools by drinking plenty of water and eating lots of fiber. Water and fiber help soften stool, which can ease the passage of stool from your body. Some foods that have fiber include:
- whole grains
However, consult your doctor to decide on a high-fiber diet that will work with your underlying cause or condition. For example, berries can be irritating if you have an inflammatory, gastric condition.