Why is my poop so dark?

Maybe melena?: Melena, by definition, is passage of dark stools stained with denatured blood. As we established in prior healthtap answers, all dark stool is not melena. Your doctor, or even an over-the-counter test that you can purchase, can check to see if your dark stool contains blood. Needed is for you to provide a sample of the dark stool. False positive results can occur based on diet & stool additives.

May be warning: If your bowel movements are a tarry black color, this may be a warning that you are bleeding somewhere in your GI tract. Blood turns to a tarry black as it moves through the intestines/colon. Sometimes, iron supplements will turn bms dark brown, even green. Blackberries may cause color changes; so can beets. And many are surprised to know peptobismol makes the stool black! check with your doctor.

Color: What color do you expect it to be? Normally, it is dark because of the presence of bilirubin biproduct, stercobilin. I'd be concerned if it were "light", it then may signify a problem with your bile excretion. On the other hand, if it is liquid and black it may signal bleeding from your gastrointestinal tract that needs to be promptly evaluated.