Black Stool Sign: 7 Serious Health Conditions That Can Cause Black Coloured Poop TheHealthSite.com What does your poop colour indicate? Pay attention. There's a lot to be learned by the colour and consistency of your stools, as well as the frequency and how easily passed Foods That Cause Dark Stools and When to Be Concerned GoodRx The Quantity of Blood Required to Produce a Tarry Stool. How much? Melena, characterized by black tarry stools, can occur with as little as 50 cc of blood in the stomach. How