Black Bowel Movement (Stool), Causes of Black Diarrhea

Normal stool (bowel movement) color is tan to brown. Sometimes it can be slightly lighter or darker depending on foods and beverages that were recently consumed as well as medication, supplements and even the speed of movement through the gut. However, there are instances when bowel movement color can be considered to be abnormal. Black stool is therefore one such case of abnormal bowel movement color.

Source:Black Bowel Movement (Stool), Causes of Black Diarrhea