Black poop can be harmless, caused by certain foods or medications, or it can be a sign of melena, meaning there’s blood in your stool. Melena happens when bleeding occurs in the upper digestive tract ...

The 52-year-old truck driver in the office of Marvin M. Lipman, Consumer Reports’ chief medical adviser, had rushed in a few minutes earlier. He had passed a large black stool (well known as an ...