Drug & supplement interaction

Chitosan + Warfarin Sodium

Warfarin Sodium brand names: Coumadin, Panwarfin, Sofarin.

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

Chitosan has a moderate interaction with Warfarin Sodium. Theoretically, chitosan might increase the risk of bleeding when taken with warfarin.

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

Chitosan and Warfarin Sodium

Here is the interaction we found between these two, with the evidence behind it.

Moderate

WARFARIN (Coumadin)

Theoretically, chitosan might increase the risk of bleeding when taken with warfarin.
In a case report, a patient taking warfarin had a significantly increased international normalized ratio (INR) after starting chitosan 1200 mg daily. The INR normalized after chitosan was discontinued and vitamin K was administered. The patient once again started taking chitosan and again had a significant increase in INR. The INR stabilized again once chitosan was discontinued. Researchers theorize that this interaction might occur because chitosan decreases absorption of fat-soluble vitamins, including vitamin K, which could increase the anticoagulant effect of warfarin.
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 concern with pairing chitosan and warfarin. Warfarin works by blocking vitamin K, which your body needs to form clots. Chitosan is a fiber-like substance that binds fats in your gut, and that may also reduce how much fat-soluble vitamin K you absorb. With less vitamin K around, warfarin can hit a little harder, meaning your INR can climb and your blood can get too thin.

This is mostly theoretical, backed by a single case report where INR rose, normalized after stopping chitosan, then rose again when it was restarted. Still, warfarin is a narrow-margin drug, so even small shifts matter. Watch for easy bruising, nosebleeds, or unusual bleeding, and please check with your pharmacist or doctor before adding chitosan.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Huang SS, Sung SH, Chiang CE. Chitosan potentiation of warfarin effect. Ann Pharmacother 2007;41:1912-4. 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

Chitosan Also Interacts With Other Medications

Chitosan has 2 moderate known drug interactions in our database — the Warfarin Sodium one above is one of them. If you take anything else, check it against the full list below.

Moderate 2 No known interaction 2,828 (incl. Warfarin Sodium)
Taking anything else?

Check Another of Your Medications Against Chitosan

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

From our Q&A

Questions About Chitosan or Warfarin Sodium

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Chitosan or Warfarin Sodium, 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 Sodium

This page covers Chitosan only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Warfarin Sodium 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).

Open the Warfarin Sodium interaction page

One more smart check

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

We hold 167 real supplement products containing Chitosan, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Chitosan. Your product may carry other ingredients that interact with Warfarin Sodium too, on top of Chitosan — 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 Chitosan and Warfarin Sodium 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 Chitosan
Steady interest

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

29 days ago today
Medication Warfarin Sodium
Top 1%

#18 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 Chitosan

What is Chitosan?

Chitosan
  • Weight management
  • Lowering cholesterol
  • Wound care
  • General digestive supplement

Chitosan is a fiber-like substance made from the shells of shrimp, crabs, and other shellfish, often marketed for weight loss and cholesterol. The evidence for these benefits is weak, and any effects appear small at best. It is generally well tolerated for short-term use, but people with shellfish allergies and those who are pregnant or breastfeeding should be cautious.

Read the full Chitosan monograph & all interactions
Medication

About Warfarin

What Is Warfarin Used For?

Brand names: Coumadin, Panwarfin, Sofarin

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 & Chitosan

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

0Major
2Moderate
0Minor
2,827No known interaction
2 Moderate 2,827 No interaction
Moderate

2 interactions

No interaction 2,827 drugs checked — show the list

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

Showing the 60 most looked-up of 2,827 medications checked with no known interaction — see the full Chitosan list.

See the full Chitosan interactions page
See every supplement checked against Warfarin Sodium, 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
Chitosan monograph › Uses, safety, and every drug interaction in one place Warfarin Sodium supplement interactions › Every supplement checked against Warfarin Sodium, 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 Chitosan and Warfarin Sodium Together: Common Questions

Can you take Chitosan with Warfarin Sodium?
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.
How serious is the Chitosan and Warfarin Sodium 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 Sodium and Chitosan?

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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.