black stools may be bcz of several reasons, here I can list most likely causes . Black Stools Caused by Food or Supplements A black stool could be caused by food, supplements, medication, or minerals. Iron supplements, taken alone or as part of a multivitamin for iron-deficiency anemia, may cause black stools or even green stools. Foods that are dark blue, black or green may also cause black stools. Substances that are often found to cause black stools include: Black licorice Blueberries Iron supplements Lead Bismuth (Pepto-bismol) Black Stools Caused By Blood: Melena Liver disease Cancer Dieulafoy lesion (a rare condition of the stomach) Erosive esophagitis (inflammation in the esophagus) Erosive gastritis (inflammation in the stomach) Intestinal ischemia (blood supply to the intestines is cut off) Peptic ulcers Tear in the esophagus (Mallory-Weiss tear) Varices (abnormally large veins) in the esophagus or stomach kindly I suggest you to consult surgeon. I hope you happy with information kindly rate it. thank you.