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Why is my stool black?

Last week or so my stool has been really dark, almost black. My stomach hasn?t hurt so I don?t know what?s going on. Should I see a doctor? What might be making this happen?
Stool color is normally light brown or slight yellow which is a result from the break-down products of bilirubin. Dark or black stool may or may not be clinically significant. If you've just had a change in your diet, consuming a large amount of dark vegetable or fruits like blue berries, then your stool would be dark for quite a few days. But if your stool changes color for no apparent dietary changes, you could be having a gastrointestinal bleeding disorder (GI bleed). GI bleeding disorder is classically divided into upper versus lower intestines. Upper GI bleeding is usually secondary to stomach or duodenal ulcers or gastritis or duodenitis. Blood from upper intestine gets broken down and by the time it gets to the rectum it is already black. Lower GI bleeding is most commonly from the large intestine. The most common source is diverticulosis, hemorrhoids, or fissures. Now the closer the source of bleeding is to the rectum, the brighter red the blood is. If you are over the age of 50 and haven't had a colonoscopy or sigmoidoscopy, I suggest that you see a gastroenterologist to get that arranged. If you have a family history of colon diseases, such as colon cancer, you should definitely have a screening colonoscopy done. Bleeding tumors are usually painless, and dark stool may be your only source of warning sign. Please schedule a visit with a doctor soon.
This answer is for general informational purposes only and is not a substitute for professional medical advice.
If you think you may have a medical emergency, call your doctor or (in the United States) 911 immediately. Always seek the advice of your doctor before starting or changing treatment. Medical professionals who provide responses to health-related questions are intended third party beneficiaries with certain rights under ZocDoc’s Terms of Service.
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