Short answer
Pepto-Bismol contains bismuth subsalicylate. Bismuth reacts with traces of sulfur in your gut and turns stool grayish-black, and it can turn the tongue black too. This is usually harmless and usually clears within a few days of stopping. Black stool that is sticky, tar-like and strongly smelling, or comes with dizziness or pain, is not explained by Pepto-Bismol.
Why does Pepto-Bismol turn stool black?
Pepto-Bismol turns stool black because its active ingredient, bismuth, combines with sulfur in your digestive tract to form bismuth sulfide, a black compound. It passes out in your stool. The effect is cosmetic. It is not a sign the medicine is harming you.
How long does black stool last after Pepto-Bismol?
Black stool from Pepto-Bismol usually lasts a few days after your last dose. The tongue can look dark for a similar time. If stool is still black more than a few days after you stop, see a clinician.
How can you tell Pepto-Bismol black stool from bleeding?
Black stool from Pepto-Bismol usually looks formed and may come with a dark tongue, while black stool from bleeding is typically sticky, tar-like and foul-smelling, often with dizziness or pain.
| Pepto-Bismol | Bleeding (melena) | |
|---|---|---|
| Texture | Usually formed, like normal stool | Sticky, tar-like |
| Smell | Usual | Very strong, foul |
| Tongue | May look dark | Normal color |
| Symptoms | None | Dizziness, weakness, pale skin, pain, vomiting blood |
If you are taking Pepto-Bismol because of stomach upset, be aware that stomach ulcers and bleeding can be the reason you feel unwell. Do not let the medicine hide a real problem.
Label warnings to know about
- Pepto-Bismol contains a salicylate related to aspirin. Children and teenagers who have or are recovering from flu or chickenpox should not take it, because of the risk of Reye's syndrome.
- Check with a pharmacist or doctor if you take blood thinners or aspirin, have an aspirin allergy, or are pregnant.
- Always read and follow the product label. If symptoms last or get worse, see a doctor.
Warning signs to know
These are signs that published medical guidance says need prompt or urgent care. The list is not complete, and ticking boxes cannot tell you whether you are ill. If you are worried, contact a clinician whatever you tick.
Questions people ask
Does Pepto-Bismol make your stool black?
Yes. Bismuth in it can turn stool black or grayish-black, and the tongue as well. This is usually harmless and temporary.
Is black stool from Pepto-Bismol dangerous?
No. But black stool from bleeding looks similar, so check the texture and how you feel. If it is sticky, tar-like or comes with dizziness or pain, get care.
Can Pepto-Bismol cause a black tongue?
Yes. This is usually harmless and fades after you stop.
How long does it take for stool to go back to normal?
Usually within a few days after the last dose.
Sources
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