Drug & supplement interaction

Phellodendron + Warfarin

Warfarin brand name: Warfarin.

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

Warfarin falls into 3 drug categories that Phellodendron can interact with; the most serious is rated moderate. Theoretically, phellodendron might increase serum levels of drugs metabolized by CYP2C9.

Read the full interaction report
SeverityModerate
LikelihoodPossible
Interactions3
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Phellodendron and Warfarin

These two interact in 3 distinct ways. Each one is explained separately below.

Why Are There 3 Interactions?

Phellodendron interacts with whole categories of medication. Warfarin falls into 3 of those categories, so it can interact with Phellodendron in 3 different ways. We’ve listed each one below — your overall risk is driven by the most serious of them (Moderate).

Moderate

CYTOCHROME P450 2C9 (CYP2C9) SUBSTRATES

1 of 3

Why this applies to Warfarin

Warfarin falls under CYTOCHROME P450 2C9 (CYP2C9) SUBSTRATES — the group Phellodendron interacts with.

Theoretically, phellodendron might increase serum levels of drugs metabolized by CYP2C9.
Phellodendron contains berberine. Preliminary clinical research shows that berberine can inhibit CYP2C9. Theoretically, phellodendron might also inhibit CYP2C9.
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 Phellodendron and warfarin. Your liver clears warfarin partly through an enzyme called CYP2C9. Phellodendron contains berberine, and early research suggests berberine may slow that enzyme down. If it does, warfarin could linger in your body longer than usual, which can push your blood-thinning effect higher than intended.

For warfarin that matters more than for most drugs, because it's a narrow window medicine where small shifts can tip you into bruising, nosebleeds, or more serious bleeding. To be clear, this is a theoretical interaction based on how berberine behaves, not solid proof in people. Still, since your INR is involved, please don't start phellodendron without checking with your doctor or pharmacist first so your levels can be watched.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Guo, Y., Chen, Y., Tan, Z. R., Klaassen, C. D., and Zhou, H. H. Repeated administration of berberine inhibits cytochromes P450 in humans. Eur J Clin Pharmacol 2012;68(2):213-217. PubMed
Moderate

CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES

2 of 3

Warfarin also falls under CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES.

Theoretically, phellodendron might increase serum levels of drugs metabolized by CYP3A4.
Phellodendron contains berberine. In vitro research and preliminary clinical research show that berberine moderately inhibits CYP3A4. Theoretically, phellodendron might also inhibit CYP3A4.
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: Phellodendron contains berberine, which lab and early human studies suggest can mildly slow down one of the liver enzymes (CYP3A4) that helps clear warfarin. If your body clears warfarin a bit slower, more can hang around, which could nudge your blood-thinning effect higher. With warfarin that matters, because it has a very narrow safe range. Too much thinning can mean easy bruising, nosebleeds, bleeding gums, or more serious bleeding.

I want to be honest that this is theoretical, based mostly on how berberine behaves in the lab, not strong proof in people taking warfarin. Still, since warfarin is so sensitive, please don't add phellodendron without checking with your pharmacist or doctor first. Your INR may need closer monitoring.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Wu X, Li Q, Xin H, Yu A, Zhong M. Effects of berberine on the blood concentration of cyclosporin A in renal transplanted recipients: clinical and pharmacokinetic study. Eur J Clin Pharmacol 2005;61:567-72. PubMed
  2. Budzinski JW, Foster BC, Vandenhoek S, Arnason JT. An in vitro evaluation of human cytochrome P450 3A4 inhibition by selected commercial herbal extracts and tinctures. Phytomedicine 2000;7:273-82. PubMed
  3. Guo, Y., Chen, Y., Tan, Z. R., Klaassen, C. D., and Zhou, H. H. Repeated administration of berberine inhibits cytochromes P450 in humans. Eur J Clin Pharmacol 2012;68(2):213-217. PubMed
  4. Hermann, R. and von, Richter O. Clinical evidence of herbal drugs as perpetrators of pharmacokinetic drug interactions. Planta Med 2012;78(13):1458-1477. PubMed
Moderate

ANTICOAGULANT/ANTIPLATELET DRUGS

3 of 3

Warfarin also falls under ANTICOAGULANT/ANTIPLATELET DRUGS.

Theoretically, phellodendron might increase the risk of bleeding when used with anticoagulant or antiplatelet drugs.
Phellodendron contains berberine. In vitro and in vivo research suggest that berberine can inhibit platelet aggregation. Theoretically, phellodendron might also inhibit platelet aggregation.
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 simple version: warfarin already thins your blood by lowering your clotting ability. Phellodendron contains berberine, and in lab and animal studies berberine seems to make platelets (the cells that help blood clot) a little less sticky. Put those two together and, in theory, your blood could become slightly too thin, which raises your bleeding risk.

What that might look like with warfarin: easy bruising, nosebleeds, bleeding gums, or blood in your urine or stool. I do want to be honest though, this concern is theoretical and only based on early lab work, not strong human studies. Still, warfarin is a narrow-margin drug where small shifts matter, so please check with your pharmacist or doctor before adding phellodendron rather than starting or stopping anything on your own.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Wu, J. F. and Liu, T. P. [Effects of berberine on platelet aggregation and plasma levels of TXB2 and 6-keto-PGF1 alpha in rats with reversible middle cerebral artery occlusion]. Yao Xue.Xue.Bao. 1995;30(2):98-102.
  2. Tripathi YB and Shukla SD. Berberis artistata inhibits PAF induced aggregation of rabbit platelets. Phytotherapy Research 1996;10:628-630.

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

Phellodendron Also Interacts With Other Medications

Phellodendron has 1,159 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 1,159 No known interaction 1,671 (incl. Warfarin)
Taking anything else?

Check Another of Your Medications Against Phellodendron

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

From our Q&A

Questions About Phellodendron 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 Phellodendron 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 Phellodendron 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 Phellodendron as Part of a Dietary Supplement Product? Check It for Interactions

We hold 393 real supplement products containing Phellodendron, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Phellodendron. Your product may carry other ingredients that interact with Warfarin too, on top of Phellodendron — 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 Phellodendron 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 Phellodendron
Top 25%

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

29 days ago today
Medication Warfarin
Top 10

#8 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 Phellodendron

What is Phellodendron?

Phellodendron
  • Digestive complaints and diarrhea
  • Inflammation and joint discomfort
  • Stress and weight management (in combination products)
  • Skin conditions (topical, traditional)
  • Antimicrobial support

Phellodendron is a traditional Chinese medicine bark (Huang Bai) that contains berberine and other plant compounds with antimicrobial and anti-inflammatory activity in lab studies. Human evidence for most uses is limited, and it is often sold in combination with other herbs, making its individual effects hard to judge. Talk with your pharmacist or doctor before using it, and avoid it during pregnancy and breastfeeding.

Read the full Phellodendron 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 & Phellodendron

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

0Major
1,159Moderate
0Minor
1,670No known interaction
1,159 Moderate 1,670 No interaction
Moderate

1,159 interactions

Showing 60 of 1,159 moderate interactions — see all 1,159 on the Phellodendron page.

No interaction 1,670 drugs checked — show the list

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

Showing the 60 most looked-up of 1,670 medications checked with no known interaction — see the full Phellodendron list.

See the full Phellodendron 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
Phellodendron 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 Phellodendron and Warfarin Together: Common Questions

Can you take Phellodendron 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 3 interactions listed for Phellodendron and Warfarin?
Warfarin belongs to more than one drug category, and Phellodendron 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 Phellodendron 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 Phellodendron?

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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.