Concerns With Pepto-Bismol Turning The Stool Black

Answer

Hello and thank you for your excellent question!

Yes, Pepto-Bismol is well known to change the color of your stool to a dark color. Although it can certainly be concerning to see your stool appear black if you aren't expecting it, it is important to know that this side effect is harmless.

Why Does Pepto-Bismol Turn Your Stool Black?

The dark color in your stool is due to bismuth sulfide, a metabolite of Pepto-Bismol after it is broken down in your system.

The mechanism behind Pepto causing a darkening of the stool is as follows:

• Pepto-Bismol contains bismuth subsalicylate.
• Bismuth subsalicylate breaks down in your stomach acid and releases bismuth ions (Bi³⁺) into the gastrointestinal tract.
• These bismuth ions react with sulfur-containing compounds (hydrogen sulfide) naturally present in the intestines from dietary sources and gut bacteria activity to form an insoluble black salt, bismuth sulfide (Bi₂S₃).
• This insoluble compound, bismuth sulfide (Bi₂S₃), is passed in your stool and causes the color of your stool to be black.

In addition to the darkening of your stool, it's not uncommon for Pepto-Bismol to cause a temporary darkening of the tongue as well.

Final Words

It is important to note that the darkening of your stool due to Pepto-Bismol use is temporary. If it persists after you have discontinued use of Pepto-Bismol, it could be an indication of other issues.

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