Understanding Melena: What Does It Mean When You Have Dark Stools? Fortis Healthcare 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. Black, Green or Bloody: What's Up With My Poop? Diet vs Disease Foods That Cause Dark Stools and When to Be Concerned GoodRx Understanding Poop Color Meaning: Gut Health from Your Stool