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.

A person should seek medical attention as soon as possible if they notice black or dark red stool or have bloody diarrhea. A person with the following symptoms may be losing a large amount of ...

One case report detailed a 93-year-old woman who reported lime-green stool after consuming a hamburger bun dyed black using yellow, blue, and red food dye. It's unclear how exactly food dye ...