Would it be possible that a lot of coffee cause rectal bleeding or blood in the stool?

Hmm: It you have dark stool that has a coffee ground consistency - please get med eval soon. If you had an ulcer - that can cause bleeding. Black, tarry, foul- smelling stool - get help asap. Possible causes ofr blood in stool include: fissures, fistulas, hemorrhoids, cancer, infections or inflammation. Get evaluated if more than a one time occurence.