Is it possible for one 30 ml of peptobismol to be enough to cause black stool for two days?

Yes: Peptobismal is capable of causing black stools. Pepto-bismol contains a little bit of bismuth and when the bismuth combines with the sulfur in your saliva and intestinal tract it makes a black colored substance which is called bismuth sulfide. This is the reason for the black stools. It is not unusual to take 2-3 days until the colon contents exposed to the medication fully clear.

Peptobis Black stool: 33 from Balt asks is it possible for one 30 ml of peptobismol to be enough to cause black stools for 2 days. YES. But why taking it? If for abd pain then bleeding from an ulcer or cancer can also cause bloody stools. If an alcoholic bleeding varices can do it. You need to review with your team and have stool tested for blood. Failure to do this may result in you dying from a curable cancer.