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EspañolWhat causes black stool? Related conditions and treatments
Overview: What should stool look like?
It’s okay to wonder if changes in stool color are something to worry about. Although the color of stools can vary from day to day, they are normally some shade of brown or maybe brown-green. That’s normal. However, if your stools turn black, should you be concerned? It could be something you ate. Or it could be a sign that you’re bleeding somewhere inside, such as your stomach, esophagus, or even your gut. If there are other problems such as abdominal pain, indigestion, nausea, bloody stools, “coffee grounds” vomiting, or similar issues, there’s a good chance something’s bleeding.
Key takeaways:
Dark stool is a common symptom that may be caused by foods, supplements, or medications. On the other hand, black and tarry stool may indicate esophageal damage, stomach ulcers, or cancers in the upper digestive tract.
Typically, dark stool does not require immediate medical attention.
Black, tarry stool that persists for more than two days or is accompanied by other symptoms, should prompt a call to your doctor. It will typically resolve without treatment within a few days, but some causes of black stool may require medical treatment.
Treatment of black stool may include changes in diet, changes in medications, taking stomach acid drugs or acid reflux treatments, or rarely surgery.
Save on prescriptions for stomach ulcers, gastritis, esophagitis, and other digestive system disorders with a SingleCare prescription discount card.
What causes black stool?
Black stool can be a temporary and relatively harmless problem caused by:
Eating dark-colored foods such as blueberries, chocolate, black licorice, or food coloring
Taking iron supplements
Using medicines that contain bismuth subsalicylate, such as Pepto-Bismol or Kaopectate
In other cases, black stool is caused by bleeding in the esophagus, stomach, or duodenum, the part of the small intestine that the stomach empties into. Stomach acid and the process of digestion turn the red blood black. Called melena, the blackened blood turns stools black and tarry. Bleeding ulcers and esophageal damage from acid reflux are the most common causes of black stools.
Esophagus problems that can cause bleeding and black stools include:
Esophagitis: inflammation of the esophagus, often due to acid reflux
Mallory-Weiss tear: a tear in the esophageal lining, usually caused by severe vomiting
Esophageal varices: swelling of the blood vessels in the esophagus due to liver disease and cirrhosis.
Esophageal cancer
Stomach problems that can cause bleeding and black stools include the following:
Peptic ulcers
Gastritis: inflammation of the stomach lining
A tear in the stomach lining
Angiodysplasia: Small blood vessels on the surface of the stomach and small intestine
Stomach cancer
Bleeding in the upper digestive tract and black stools can also be caused by:
Abnormal blood vessels (angiodysplasia)
Medication side effects, especially from blood thinners or nonsteroidal anti-inflammatory drugs (NSAIDs) like aspirin
Radiation treatment
Injury from medical procedures
Swallowing a foreign object
Trauma
In some cases, bleeding in the small intestine could cause black and tarry stools, but healthcare professionals won’t investigate the lower gastrointestinal tract until they’ve ruled out bleeding in the upper GI tract. Bleeding in the lower small intestine, large intestine, and rectum usually shows up as red or bloody stools.
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Should I be worried about black stool?
All by itself, black stool that is not sticky should not be a cause for worry. It's a common problem that is sometimes caused by a dietary factor and should resolve after a couple of days. However, if there’s bleeding in the upper digestive tract, there will usually be other symptoms such as abdominal pain, nausea, difficulty swallowing, or blood in the vomit or stools. Additionally, the poop will be sticky or “tarry” and will probably smell awful, or at least more awful than usual. In people with a history of stomach ulcers, gastroesophageal reflux disease (GERD), or advanced cases of liver cirrhosis, black stool will likely indicate bleeding in the esophagus or stomach. People with these medical conditions need to take black stool more seriously than the average person.
Keep in mind, though, that internal bleeding can be serious, so see a healthcare provider if black stools persist for longer than two days or are accompanied by other symptoms. It usually takes a minimum of about four tablespoons (1/4 cup) of blood in the stomach to turn stools black and tarry. That’s a fair amount of blood, but there could be even more than that in the stool. For this reason, anemia and severe blood loss are potentially serious complications of untreated black stool. Anemia, or a low red blood cell count, requires medical attention. At the very least, a source of bleeding needs to be ruled out. However, severe blood loss is a medical emergency. Anyone with black stools who experiences symptoms of a large amount of blood loss such as confusion, lightheadedness, pale skin, a fast heartbeat, or fast breathing should go to an emergency room right away.
How is the cause of black stool diagnosed?
A healthcare provider is needed to definitively diagnose the medical condition that may be causing black stools. Diagnosis starts with a medical history and a physical examination. Be prepared to answer questions about past problems with the digestive system, the types of foods being eaten, and medications being taken. An important part of the history will be determining how much blood is being lost, so the number of dark stools and any other signs of GI bleeding are important to the history.
A stool sample may be required. This will determine whether blood is being lost in the GI tract. Blood tests will likely be ordered. A complete blood count (CBC) will show whether the person is anemic. In some cases, the examiner may perform an endoscopy. In this procedure, the examiner will pass a tube with a camera into the esophagus, stomach, and duodenum to spot any tears, ulcers, or broken blood vessels. CT, X-ray imaging, or an angiogram may also be used to pinpoint the place that’s bleeding. An angiogram images the flow of blood, so it can identify the source of bleeding. Contrast dye will be used, so make sure the examiner knows about any allergies to contrast dye or any kidney disease. In some cases, the examiner may need to examine the intestines through medical imaging procedures or a colonoscopy.
How long does black stool last?
If black stool is caused by something in the diet or as a direct result of medicine, then it will go away once the offending food or medicine is stopped. If it is caused by bleeding, it may take longer. An esophageal tear usually resolves without treatment in a few days, just like a cut anywhere else. Bleeding ulcers usually require a proton pump inhibitor (PPI) to heal. A stomach ulcer takes about six to eight weeks or more to completely heal. However, the bleeding will usually stop well before then.
How to stop black stool
The cause of black stools will determine how to get rid of them. Black stools caused by something in the diet are harmless and go away when the food or supplement is stopped. Black stool treatments for bleeding conditions are a different matter. Some, like esophageal tears, bleeding ulcers, or gastritis, can sometimes get better on their own, but not always.
People with esophagitis, stomach ulcers, or gastritis may need to take medications that control stomach acid, such as proton pump inhibitors (PPIs) like omeprazole (Prilosec), pantoprazole (Protonix), and esomeprazole (Nexium) or H2 blockers like cimetidine (Tagamet) and famotidine (Pepcid). Ulcers may also require antibiotics to eliminate the H. pylori bacterial infection that may be causing them. Tumors or foreign objects usually need to be removed surgically. Some tears or ulcers may also require surgical treatment.
Recurrent black stool
People with stomach ulcers or GERD are more likely to experience bleeding in the upper GI tract, so black stools can happen regularly. There are long-term complications from recurrent GERD and peptic ulcers. Recurrent esophagitis caused by GERD can scar the esophageal tissue and narrow the esophagus. Recurrent ulcers can damage the stomach lining. Long-term complications of stomach ulcers include perforation of the stomach and stomach cancer.
People with recurrent stomach ulcers or GERD can keep them at bay by following a few basic lifestyle changes:
Avoid acid-producing foods like dairy products, carbonated beverages, coffee, and acidic foods like citrus fruits and tomatoes
Avoid foods that hurt the stomach like alcohol, spicy foods, fried foods, and fatty foods
Avoid NSAIDs like aspirin and ibuprofen
Quit smoking
Eat small meals throughout the day
Use antacids before meals
Practice stress management and reduce stress in general
RELATED: The best diet for acid reflux: 3 foods to eat—and 8 to avoi
Most importantly, black stools may be caused by bleeding
Black stools may be caused by something harmless in the diet or by bleeding. If stools turn black and tarry and there are other symptoms of gastrointestinal problems, then bleeding may be the cause. Internal bleeding can have serious consequences. See a healthcare provider, such as a specialist in gastroenterology, if you suspect internal bleeding. If there are no other symptoms but black stools persist for longer than two days, again, see a healthcare provider. However, people with chronic conditions like cirrhosis of the liver should immediately contact a doctor if their stools turn black.
Only a healthcare provider can figure out if the bleeding is a problem and what is causing it. Remember that black stools may mean that the body is currently losing blood. If any symptoms of blood loss such as pallor, lightheadedness, confusion, a fast heartbeat, or difficulty breathing are experienced, immediate medical attention is needed.
FAQs about the causes of black stool
Is black stool an emergency?
Fortunately, temporary black stool is usually not an emergency. It only becomes an emergency if enough blood has been lost to produce symptoms. These symptoms usually don’t manifest until 15% or more of the body’s blood has been lost. The first signs of serious blood loss are pale skin, lightheadedness, a fast heart rate, and fast breathing.
What should I do if my poop is black?
If your poop turns black, don’t panic. It may be due to something you ate. However, if the black poop has a foul smell, is sticky, or there are other problems like stomach pain, heartburn, bloating, or bloody stools, the problem could be gastrointestinal bleeding. That’s not good, so call a healthcare professional for medical advice.
Which foods cause dark stools?
Dark foods can cause dark stools. These include blueberries, chocolate, or dark licorice. Some foods, like beets, will cause dark but reddish stools.
What’s next? Additional resources for people with black stool
Test and diagnostics
Hematemesis, melena, and hematochezia, The History, Physical, and Laboratory Examinations
Tests for stomach cancer, American Cancer Society
Treatments
Gastritis treatment and medications, SingleCare
GERD treatment and medications, SingleCare
The best diet for acid reflux: 3 foods to eat—and 8 to avoid, SingleCare
Ulcer treatments and medications, SingleCare
Scientific studies and clinical trials
More information on related health conditions
Esophageal varices, StatPearls
Gastrointestinal bleeding, StatPearls
Hemorrhage, StatPearls
Ulcerative colitis treatments, SingleCare
Ulcerative colitis vs. Crohn’s, SingleCare
Colitis treatments, SingleCare
Colon cancer treatments, SingleCare
Hemorrhoid treatments, SingleCare