Drug & supplement interaction

Bismuth + Warfarin

Warfarin brand name: Warfarin.

Moderate Interaction
Medically reviewed by · Updated September 2026
The bottom line Moderate

Warfarin falls into 2 drug categories that Bismuth can interact with; the most serious is rated moderate. Theoretically, use of bismuth subgallate or other bismuth salts might reduce the effects of anticoagulant/antiplatelet drugs.

Read the full interaction report
SeverityModerate
LikelihoodPossible
Interactions2
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Bismuth and Warfarin

These two interact in 2 distinct ways. Each one is explained separately below.

Why Are There 2 Interactions?

Bismuth interacts with whole categories of medication. Warfarin falls into 2 of those categories, so it can interact with Bismuth in 2 different ways. We’ve listed each one below — your overall risk is driven by the most serious of them (Moderate).

Moderate

ANTICOAGULANT/ANTIPLATELET DRUGS

1 of 2

Why this applies to Warfarin

Warfarin falls under ANTICOAGULANT/ANTIPLATELET DRUGS — the group Bismuth interacts with.

Theoretically, use of bismuth subgallate or other bismuth salts might reduce the effects of anticoagulant/antiplatelet drugs.
In humans, bismuth subgallate activates factor XII and accelerates the coagulation cascade.
Severity Moderate Likelihood Possible Evidence D

Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the gist for warfarin and bismuth. Warfarin keeps your blood from clotting too easily, and it has a very narrow safety window, so even small shifts can matter. On paper, some bismuth salts (like bismuth subgallate) may nudge the clotting process to speed up a little, which could work against warfarin and make it slightly less effective. In real life that could mean less protection from clots.

Important: this is theoretical, based mostly on how bismuth behaves in the lab, not on strong patient studies. Also keep in mind that many stomach products use bismuth subsalicylate, which contains a salicylate (aspirin-like) and can tip things the other way toward more bleeding. Because warfarin is so sensitive, please check with your pharmacist or doctor before using bismuth regularly. Don't change your warfarin on your own.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Callanan, V., Curran, A. J., Smyth, D. A., and Gormley, P. K. The influence of bismuth subgallate and adrenaline paste upon operating time and operative blood loss in tonsillectomy. J Laryngol Otol 1995;109(3):206-208. PubMed
Moderate

WARFARIN (Coumadin)

2 of 2
There is some concern that bismuth subsalicylate might increase the effects of warfarin.
In one case, a patient treated with warfarin had an increase in international normalized ratio (INR), from 2.56 to 3.54, following intake of bismuth subsalicylate 30 mL every 4 hours for 3 days. However, this interaction resulted from the displacement of warfarin from plasma protein binding sites by salicylate, which increased the free active form of warfarin. Therefore, this interaction is not likely to occur with other bismuth salts.
Severity Moderate Likelihood Possible Evidence D

Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the gist: many popular stomach remedies aren't just bismuth, they're bismuth subsalicylate, and that salicylate part acts a lot like aspirin. The worry isn't with the bismuth itself, it's the salicylate. Warfarin rides through your blood stuck to proteins, and salicylate can bump it off, leaving more free, active warfarin floating around. That can nudge your blood toward being too thin.

In practice this could show up as a higher INR or easier bruising, nosebleeds, or bleeding that's slow to stop. The evidence here is just a single case report, so it's a soft signal, not a sure thing. But since warfarin is a drug where small shifts matter, please check with your pharmacist or doctor before using these products regularly, and don't change your warfarin on your own.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Bingham AL, Brown RO, Dickerson RN. Inadvertent exaggerated anticoagulation following use of bismuth subsalicylate in an enterally fed patient receiving warfarin therapy. Nutr Clin Pract 2013;28(6):766-9. PubMed

What These Ratings Mean

Every interaction above is graded three ways — here’s the key to each label.

Severity how clinically significant the interaction is
Major

Clinically significant. Avoid the combination, or use only under close professional supervision.

Moderate

Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.

Minor

Generally not serious. Be aware of it and mention it to your pharmacist.

Likelihood how strong the evidence is that the interaction actually happens in people
  • LikelyWell-controlled human studies have demonstrated the likely existence of this interaction.
  • ProbableInteraction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
  • PossibleInteraction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.
  • UnlikelyInteraction has been demonstrated in animal or in lab research but has been shown not to occur in humans.
Evidence the quality of the studies behind the rating (graded A–D)
  • AHigh-quality meta-analysis (quantitative systematic review).
  • BCase-control study.
  • CConsensus.
  • DAnecdotal evidence.

These ratings are for information only. Never start, stop, or otherwise change your therapy before speaking with your provider.

Keep it in perspective

Bismuth Also Interacts With Other Medications

Bismuth has 124 moderate known drug interactions in our database — the Warfarin one above is among them. If you take anything else, check it against the full list below.

Moderate 124 No known interaction 2,706 (incl. Warfarin)
Taking anything else?

Check Another of Your Medications Against Bismuth

Covers the 2,830 medications we’ve checked against Bismuth. Pick one to open its full report.

From our Q&A

Questions About Bismuth or Warfarin

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Bismuth or Warfarin, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Warfarin

This page covers Bismuth only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Warfarin page lists 361 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Alfalfa (major), American Ginseng (major), Beer (major) and Cannabis (major).

By severity: 16 major · 301 moderate · 44 minor.

From our pharmacist’s overview on the Warfarin page

“People take warfarin to prevent dangerous clots, and many are the same people reaching for glucosamine for sore joints or a multivitamin containing vitamin K, which makes this a list that deserves genuine respect. Of the 361 supplements on file for warfarin, 16 carry a major rating, and the danger runs in both directions: some add to w…”

Reviewed by 2 · Jul 18, 2026

Open the Warfarin interaction page

One more smart check

Taking Bismuth as Part of a Dietary Supplement Product? Check It for Interactions

We hold 65 real supplement products containing Bismuth, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Bismuth. Your product may carry other ingredients that interact with Warfarin too, on top of Bismuth — and those would not show on this page. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Bismuth and Warfarin Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement Bismuth
Steady interest

#806 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Warfarin
Top 10

#7 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Supplement

About Bismuth

What is Bismuth?

  • Upset stomach and indigestion
  • Diarrhea
  • Heartburn and nausea
  • Helicobacter pylori treatment (with other drugs)
  • Traveler's diarrhea prevention

Bismuth is a metallic element used in medicine mostly as bismuth subsalicylate (the active ingredient in some well-known stomach remedies) to ease upset stomach, heartburn, nausea, and diarrhea. It is generally well tolerated for short-term use, but it can cause harmless black stools or a dark tongue, and because most products contain salicylate, it carries cautions similar to aspirin. Always follow the label and check with a pharmacist before regular use.

Read the full Bismuth monograph & all interactions
Medication

About Warfarin

What Is Warfarin Used For?

Brand name: Warfarin

Warfarin sodium tablets and Jantoven tablets are both used to prevent and treat venous thrombosis (blood clots in the veins) and pulmonary embolism (a clot in the lungs). They are also used to prevent clot-related complications in people with atrial fibrillation (an irregular heart rhythm) or who have had a heart valve replaced.

In people who have had a heart attack, warfarin is used to reduce the risk of death, another heart attack, stroke, or other clotting events. It does not dissolve an existing clot, but it helps prevent the clot from growing and stops new dangerous clots from forming.

See full Warfarin drug information
Keep checking

Other Drugs & Bismuth

Browse every other medication we’ve checked against Bismuth — both the ones with a known interaction and the ones without. Select any drug for the full detail.

0Major
124Moderate
0Minor
2,705No known interaction
124 Moderate 2,705 No interaction
Moderate

124 interactions

Showing 60 of 124 moderate interactions — see all 124 on the Bismuth page.

No interaction 2,705 drugs checked — show the list

We also checked Bismuth against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 2,705 medications checked with no known interaction — see the full Bismuth list.

See the full Bismuth interactions page
See every supplement checked against Warfarin, ranked by severity
Sources

Sources & How We Checked

Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

Keep exploring
Bismuth monograph › Uses, safety, and every drug interaction in one place Warfarin supplement interactions › Every supplement checked against Warfarin, ranked by severity Warfarin drug information › The full plain-English guide to this medication Supplement interaction checker › Check any supplement or product against your medications Browse medications A–Z › Every drug we've checked against herbs & supplements Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking Bismuth and Warfarin Together: Common Questions

Can you take Bismuth with Warfarin?
There is a moderate interaction, so it may be acceptable with monitoring or timing changes — but check with your pharmacist first. Read the full details on this page and confirm with your pharmacist before combining them.
Why are there 2 interactions listed for Bismuth and Warfarin?
Warfarin belongs to more than one drug category, and Bismuth interacts with each of those categories a little differently. We list every one so nothing is missed — your overall risk is driven by the most serious of them.
How serious is the Bismuth and Warfarin interaction?
We rate it Moderate. This combination may require monitoring, a dose adjustment, or separating the times you take each one. Consult your pharmacist before using them together.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Still Have a Question About Warfarin and Bismuth?

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This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.