Any time someone's stool is black-- this is cause for concern.
If bleeding occurs in the stomach or the upper part of the small intestine, the stool may turn black and sticky, described medically as black, tarry stool. Generally, black, tarry stool also is foul-smelling. This change in color and consistency occurs because of chemical reactions to blood within the intestine that are caused by digestive enzymes within the intestines.
The only time when black stool is normal is if he were to be taking iron supplements.
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