My boyfriend has had really bad diarrhea and now his stool is black. what should we do?

The topic tags you chose indicate you know that black, tarry stool (melena) usually means internal bleeding in the intestinal tract, like from an ulcer (and many other possible causes). He needs to see a doctor or clinic right away. If he feels weak, dizzy or light-headed, he must be seen immediately, even if it means a nighttime visit to an emergency room. Good luck.

Black stool is often a sign of internal bleeding. It means that he should be checked out in the emergency room immediately. Don’t hesitate. Good luck.