Gastro Health

Black or Tarry Stools - Causes, Diagnosis, Prevention and Treatment

Written by
Dr. Sneha Kannan
and medically reviewed by Dr. Jagdish Singh

Published on Sep 21, 2019 and last reviewed on Oct 03, 2019   -  4 min read



Black or tarry stools can be due to change in diet, or it can be a sign of some underlying medical condition. Read about all the possible causes and treatment options.

Black or Tarry Stools - Causes, Diagnosis, Prevention and Treatment

Black or tarry stool is not always something to panic about. Many common causes like food, iron supplements, and other medicines can make your stool appear black. When food is not digested properly in the stomach because of some surgery or you eat licorice and beet, your stool will appear black or red. Black stool does not always mean you are bleeding internally. But, if you notice that your stool is black and has a foul smell often, then it is best to consult a doctor, as it can also be caused due to bleeding or injury in your gastrointestinal tract. So if you notice a change in color, always consult your doctor so he or she can rule out if blood is present in the stool with a simple test. Black stool that results from bleeding is called melena.

Points to Remember:

  1. The most common cause is eating dark foods or iron supplements.

  2. Bleeding ulcer also commonly causes melena.

  3. Blood in stools indicates an upper gastrointestinal problem.

  4. A stool test can detect blood in stools.

  5. Always consult your doctor if your poop is black and you have vomiting or diarrhea.

What Are the Causes of Black or Tarry Stools?

Some of the common causes are:

  • Iron Supplements - Black stool is the most common side effect of iron supplements, which are given for anemia. The other common side effects of iron tablets are nausea, constipation, heartburn, and abdominal pain. If you notice these side effects, consult your doctor to change or stop iron supplements.

  • Dark Foods - Eating dark-colored foods can result in black stools. Examples of such foods include black licorice, chocolate cookies, blueberries, beets, etc. But once you stop eating them, your stool should not be black anymore.

  • Gastritis - Inflammation of the stomach lining is called gastritis. It can result from the indiscriminate use of painkillers, eating spicy food, smoking, and bacterial or viral infection.

  • Bismuth Medicines - Drugs that contain Bismuth subsalicylate is used to treat an upset stomach and heartburn. The Bismuth in these medicines makes your tongue and stool black. Get immediate medical help if you have a buzzing sound in your ears or do not feel fine after taking Bismuth medicines.

  • Esophageal or Gastric Cancer - Bleeding in the gastrointestinal tract can also be due to esophageal or gastric cancer. Some of the symptoms that indicate esophageal cancer are difficulty swallowing, unintentional weight loss, chest pain, indigestion, and coughing. The symptoms of gastric cancer are tiredness, bloating, stomach pain, nausea, and vomiting.

  • Mallory-Weiss Tear - Your esophagus can tear due to intense cough or vomiting. This can result in internal bleeding. Most tears heal on their own, but if you notice symptoms like blood in vomit, weakness, dizziness, difficulty breathing, pale skin, and chest pain, get immediate medical help.

  • Esophageal Varices - Swollen veins in the esophagus are called esophageal varices. These veins can rupture and bleed, resulting in melena. This is commonly seen in people suffering from liver disease. The other symptoms of varices are jaundice, easy bruising, abdominal swelling, blood in vomit, and losing consciousness.

  • Diverticulosis - The formation of tiny pockets (diverticula) in the lining of the bowel is called diverticulosis. When this gets infected, inflamed, or ruptures, it can result in gastrointestinal bleeding.

  • Constipation - Straining to pass hard stools can cause blood in the stool.

  • Ulcerative Colitis - Ulcerative colitis can result in pus-producing ulcers, which can bleed and cause black stools.

  • Inflammatory Bowel Disease (IBD) - IBD can cause inflammation in your digestive tract, and can cause tarry stools.

  • Colon Polyps - Small painless clumps seen on the lining of the colon are called colon polyps. These polyps can rupture and bleed.

  • Hemorrhoids - Swollen veins in the anus or rectum are called hemorrhoids or piles.

How Can the Cause of Black or Tarry Stools Be Diagnosed?

After taking a complete medical and family history, your doctor will perform a physical examination to determine the cause. The doctor might tell you to perform the following tests:

  • Blood tests.

  • Stool test.

  • MRI, X-ray, and CT scans are used to see if there is any pathology in the gastrointestinal tract.

  • Gastroscopy or colonoscopy to assess the gut condition.

What Are the Treatment Options Available for Black Stools?

Treatment for black stools depends on the cause. Treating the underlying condition will treat this problem. The treatment options include:

  • Sitz bath for preventing hemorrhoids from bleeding.

  • Stool softener to treat constipation.

  • Antibiotics and immunosuppressants for IBD and infection.

  • Antacids for bleeding ulcers.

  • Surgery is necessary for vein abnormalities, polyps, and obstructions.

  • For cancer, chemotherapy, radiation therapy, and surgery might be needed.

Too much bleeding can result in severe anemia, which can also be fatal. If you have developed severe anemia, a blood transfusion might be necessary.

How Can Black Stools Be Prevented?

Some of the causes of black stools can be prevented by:

  • Drinking plenty of water.

  • Eating a diet rich in fiber.

  • Consume whole grains.

  • Avoid eating processed meats.

  • Avoid consuming refined sugars, trans fat, and saturated fat.

  • Consume more fruits and vegetables.

  • Exercise regularly.

If the cause is food, then black stool is not a problem. If it is accompanied by other symptoms, then consult a doctor online.

Last reviewed at:
03 Oct 2019  -  4 min read




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