 [ Symptoms ] what causes black poop i had the stomach flu for 4 days with vomiting and black diarhia i have been better for 2 days however i took pepto bismal for stomach ache yesterday today i had a bowel movement and it was still liquid and black could this be just the infection coming out or is it something more [ Disease ] pepto bismol or pink bismuth specifically is known to turn the tongue andor stool black temporarily this condition can persist for a few days after you take the product the effect depends on how much pepto you took too if the black stool goes away after a few days you probably have nothing to worry about if it persists for more than a week you probably should see a health care provider bleeding in the gastrointestinal tract everything from your stomach to your rectum can cause the stool to turn black i am going to assume however that the situation is temporary due to the use of pink bismuth wishing you all the best for a speedy recovery