Hi
Welcome to the MedHelp forum!
Black stool can be due to medicine you took. It can also be due to bleeding into gut such as due to acidity, IBS, inflammatory bowel disease and even due to gastroenteritis. If this repeats it self get the stool tested for occult or hidden blood. Hope this helps. Take care!
yes i know pepto will do that to me for sure. im not a dr but i really dont think you have anything to worry about