What can cause dark stool?

Diet, blood: Stool will vary from light to dark depending upon the diet. Diets rich is red meat for instance will darken the stool color. If there is GI bleeding then the stool may become black. This requires evaluation by your gastoenterlogist as the source of the bleeding must be discovered and corrected.

Melena?: Black, malodorous, sticky stool can be due to GI bleeding.