What are some causes of black stool in adults?

Black stools in adults may be the result of bleeding in the upper part of the small intestine, the esophagus or the stomach, according to MedlinePlus. A person who is taking iron supplements, bismuth subsalicylate or black licorice may also have black stools, according to Mayo Clinic.

Bleeding in the upper part of a person's digestive tract may result from conditions such as a bleeding ulcer in the stomach, abnormal blood vessels, inflammation of the stomach, or overgrown veins in the esophagus or stomach, notes MedlinePlus. Anyone experiencing changes in stool color or texture should make an appointment to see a doctor.