Bismuth subsalicylate: what it treats, how to take it, side effects
Last updated September 3, 2026.
Bismuth subsalicylate is the pink stuff for diarrhea, heartburn, and upset stomach. You may know it as Pepto-Bismol. It works three ways at once: it decreases the flow of fluids and electrolytes into the bowel, reduces inflammation inside the intestine, and may kill the organisms that cause diarrhea.
What does it treat?
Diarrhea, heartburn, and upset stomach in adults and children 12 and older. That is MedlinePlus's list, and the label matches it. For diarrhea, one stop rule matters most: if symptoms get worse or the diarrhea lasts longer than 48 hours, stop taking it and call your doctor.
How do you take it?
By mouth as a liquid, tablet, or chewable tablet, with or without food. The chewable-tablet label runs: 2 tablets every half hour to an hour as needed, chewed or dissolved in the mouth, no more than 8 doses (16 tablets) in 24 hours, and no more than 2 days for diarrhea. Swallow regular tablets whole, shake the liquid well, and drink plenty of clear fluids - replacing what diarrhea takes out is half the treatment. Taken as needed, missed doses are rarely an issue.
Side effects to know
- Expected: a darkened tongue and dark stools. MedlinePlus says this is harmless and goes away a few days after you stop.
- Serious: ringing or buzzing in your ears means stopping the medication and calling your doctor immediately - that is the salicylate in the formula talking. Overdose signs (collapse, seizure, trouble breathing, unresponsiveness) are a 911 call.
Who should not take it?
Anyone allergic to aspirin or other salicylates, and anyone already taking other salicylate products - the label's allergy alert is explicit. The Reye's syndrome warning is the other hard rule: children and teenagers who have or are recovering from chickenpox or flu-like symptoms should not use this product. Ask your doctor first if you have had an ulcer, a bleeding problem, bloody or blackened stools, kidney disease, a fever, or mucus in the stool. Interactions worth flagging to your pharmacist: blood thinners like warfarin, daily aspirin, and medications for diabetes, arthritis, or gout - and tetracycline antibiotics, which need to be taken at least 1 hour before or 3 hours after bismuth subsalicylate. Pregnant or breastfeeding: ask your doctor first.
When is it an emergency?
Ringing or buzzing in the ears after doses means stop and call your doctor immediately. Bloody or black stools that are not the harmless bismuth darkening, or diarrhea with fever, mean medical care. For an overdose, call Poison Control at 1-800-222-1222; collapse or trouble breathing means 911. Pymander's escalation routing is built and tested specifically for this class of decision; see the safety architecture working paper.
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Common questions
Why did Pepto-Bismol turn my tongue and stool black?
The bismuth does it, and it is harmless. MedlinePlus says darkening of the stool or tongue while taking bismuth subsalicylate is expected and usually goes away within a few days after you stop. It looks alarming and means nothing.
Can kids take Pepto-Bismol?
Not young children, and not teenagers recovering from viral illness. The product is for adults and children 12 and over. The label carries the Reye's syndrome warning: children and teenagers who have or are recovering from chickenpox or flu-like symptoms should not use it, because of the salicylate it contains - the same family as aspirin.
Can I take Pepto-Bismol with my other medications?
Ask your pharmacist first if you take blood thinners like warfarin, daily aspirin, or medications for diabetes, arthritis, or gout - MedlinePlus names all of these. Tetracycline antibiotics need spacing: take them at least 1 hour before or 3 hours after bismuth subsalicylate.
How long can I take Pepto-Bismol for diarrhea?
Two days. The label says use until diarrhea stops but not more than 2 days, and MedlinePlus sets the same boundary: if symptoms get worse or the diarrhea lasts longer than 48 hours, stop and call your doctor. Persistent diarrhea needs a cause, not more pink liquid.
Can I drink alcohol while taking bismuth subsalicylate?
Neither the FDA label nor MedlinePlus lists a specific alcohol interaction. Alcohol irritates the stomach and dehydrates you while you are treating exactly those problems, so skipping it until you are well is the sensible default.
Is Pepto-Bismol related to aspirin?
Yes - the subsalicylate in the name is a salicylate, aspirin's family. That is why the label says do not take it if you are allergic to salicylates including aspirin or are taking other salicylate products, and why the Reye's syndrome warning applies to kids and teens.