Dark stool vs black stool the difference can be serious. Dark brown stool is often food or iron related. Black, tarry stool may indicate internal bleeding and needs urgent medical attention. Why Black Dark Brown Tarry Stool Appears After Wearing Hair Nets And How This One Product Changed My Experience Foods That Cause Dark Stools and When to Be Concerned GoodRx Melanosis Coli Gastroenterology & Hepatology of CNY