Its active ingredient (bismuth subsalicylate) can cause your stool to turn black or gray. This side effect is harmless and temporary, lasting only a couple days after you stop taking Pepto Bismol.

You should always see a doctor if you have black poop, especially if it's also sticky or tarry. Mild dehydration can lead to constipation and stool that's darker brown and harder than normal.

Medically reviewed by Kumkum Sarkar Patel, MD Bleeding in the gastrointestinal tract and colon cancer can cause black poop ...

A wide range of colors is usual. In infants, the main reasons for changes in stool color are age, diet, and health. The poop of newborns is almost black, while older infants tend to have yellow or ...