What are the causes of dark stool?

Written by cindi pearce | 13/05/2017

Dark stool is caused by upper GI tract bleeding. Generally, we get concerned when we see blood or red-tinged faeces, but dark, tarry stool can indicate that something is wrong and is as much of a concern as red, obviously bloody stool.

Pay Attention

Tarry, black stool is called melena, and it is often foul smelling. When your stool is black, it might not register with you, as bloody, red stool would, that something is going on. When blood in the stool is minimal or presents as black, tarry faeces, blood may be detected only by a fecal occult blood test, which is why you should have this done at your annual doctor's visit.


When stool is black, that means that the bleeding has not occurred in your rectum, large bowel or anus, which are parts of the lower GI tract. It is also means that it is not hemorrhoidal bleeding, which is generally quite red and fresh. It also pretty much eliminates diverticulosis, which happens when pouches develop in the colon, and which results in red blood in the stool.


Bloody stool that originates in the upper GI tract turns black because it's in your system for a longer time and it is exposed to juices that are produced by the digestive system. If you are bleeding in your stomach, oesophagus or small intestine, it takes a while for the blood to exit and, when it does, it turns your stool black. Bleeding in the upper GI tract can be caused by inflammation that may be the result of taking medicines such as naproxen, ibuprofen or aspirin. Stomach ulcers can also cause bleeding, and the stool is black as a result.

Possible Influences

If you have drunk red wine or have eaten black liquorice, this can cause black stools, according to Ourgardengang.com. Iron pills, Pepto-Bismol and paprika-filled foods can also cause tarry poop. However, if your stools are black and you haven't consumed any of the above, you need to consult with your physician.


The ideal bowel movement consists of a soft stool that floats to the top of the water in the toilet. It is brown, not red or black. Soft stools move through your system faster than those that are hard, which helps prevent constipation and haemorrhoids and puts you at a lower risk for getting diverticulitis, which is, essentially, hernias of the small colon. Eating sufficient amounts of fibre result in soft stools or "floaters," according to Ourgardengang.com.

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