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.

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.

A 72-year-old woman with a history of lung cancer and hypertension presents to the emergency department with diarrhea, which has persisted for 1 to 2 weeks. The patient is on a stable chemotherapy ...