Drug & supplement interaction

Phellodendron + Metformin, Rosiglitazone

Metformin, Rosiglitazone brand name: Avandamet.

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

Metformin, Rosiglitazone 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 Metformin, Rosiglitazone

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. Metformin, Rosiglitazone 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 Metformin, Rosiglitazone

Metformin, Rosiglitazone 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

Avandamet combines two diabetes medicines. The piece that matters here is rosiglitazone, which your liver clears using an enzyme called CYP2C9. Phellodendron contains berberine, and early research hints that berberine can slow that enzyme down. If it does, rosiglitazone could build up a bit more than usual, which might nudge your blood sugar lower and add to side effects like swelling in the ankles, weight gain, or feeling extra tired. The metformin half is handled differently and isn't really affected by this enzyme.

I want to be honest that this is theoretical, based on lab and pharmacology reasoning rather than strong human studies, so don't panic. Still, since you're managing diabetes, check with your pharmacist or doctor before adding phellodendron, and watch for signs of low blood sugar.

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

ANTIDIABETES DRUGS

2 of 3

Metformin, Rosiglitazone also falls under ANTIDIABETES DRUGS.

Theoretically, phellodendron may increase the risk of hypoglycemia when taken with antidiabetes drugs.
Phellodendron contains berberine. Clinical research shows that berberine may lower blood glucose levels. Theoretically, phellodendron might also lower blood glucose levels.
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: Avandamet pairs metformin and rosiglitazone, and both already work to bring your blood sugar down. Phellodendron contains berberine, which lab and some human studies suggest can also nudge blood sugar lower. So the worry is mostly about stacking two blood-sugar-lowering effects on top of each other, which could push you into hypoglycemia.

If your sugar drops too far, you might feel shaky, sweaty, dizzy, irritable, or get a fast heartbeat. To be clear, this is a theoretical concern based on how berberine behaves, not strong proof. Still, it's worth a quick chat with your pharmacist or doctor before adding phellodendron, and keep an eye on your readings if you do start it. Don't change your Avandamet on your own.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Zhang Y, Li X, Zou D, et al. Treatment of type 2 diabetes and dyslipidemia with the natural plant alkaloid berberine. J Clin Endocrinol Metab 2008;93:2559-65. PubMed
  2. Yin, J., Xing, H., and Ye, J. Efficacy of berberine in patients with type 2 diabetes mellitus. Metabolism 2008;57(5):712-717. PubMed
  3. Zhang, H., Wei, J., Xue, R., Wu, J. D., Zhao, W., Wang, Z. Z., Wang, S. K., Zhou, Z. X., Song, D. Q., Wang, Y. M., Pan, H. N., Kong, W. J., and Jiang, J. D. Berberine lowers blood glucose in type 2 diabetes mellitus patients through increasing insulin re
  4. Wei, W., Zhao, H., Wang, A., Sui, M., Liang, K., Deng, H., Ma, Y., Zhang, Y., Zhang, H., and Guan, Y. A clinical study on the short-term effect of berberine in comparison to metformin on the metabolic characteristics of women with polycystic ovary syndro
Moderate

METFORMIN (Glucophage)

3 of 3
Theoretically, phellodendron might increase the therapeutic and adverse effects of metformin.
Phellodendron contains berberine. In vitro and animal studies show that berberine can increase the systemic exposure and half-life of metformin, potentially increasing metformin's effects and side effects. This interaction seems to be most apparent when berberine is administered 2 hours prior to metformin. Taking berberine and metformin at the same time does not appear to increase systemic exposure to metformin. It is unclear if phellodendron might have this same effect.
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

Your Avandamet combines two diabetes medicines, and the part we care about here is the metformin. Phellodendron contains berberine, and in lab and animal studies berberine seems to slow how fast the body removes metformin. If less metformin is cleared, more of it can hang around, which could nudge its effects (and side effects) up a bit.

For you that might mean more of metformin's usual complaints, like nausea, an upset stomach, or diarrhea, and possibly blood sugar running lower than expected. Worth knowing: this was mostly seen when berberine was taken a couple of hours before metformin, not at the same time, and it's theoretical rather than proven in people. Before adding phellodendron, check with your pharmacist or doctor.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Lyu Y, Zhang Y, Yang M, et al. Pharmacokinetic interactions between metformin and berberine in rats: Role of oral administration sequences and microbiota. Life Sci. 2019;235:116818. 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

Phellodendron Also Interacts With Other Medications

Phellodendron has 1,159 moderate known drug interactions in our database — the Metformin, Rosiglitazone 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. Metformin, Rosiglitazone)
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.

Everything else you take

See Every Supplement That Interacts With Metformin, Rosiglitazone

This page covers Phellodendron only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Metformin, Rosiglitazone page lists 315 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Beer (major), Siberian Cocklebur (major), Wine (major) and Acai (moderate).

By severity: 4 major · 268 moderate · 43 minor.

From our pharmacist’s overview on the Metformin, Rosiglitazone page

“Avandamet pairs metformin with rosiglitazone to manage type 2 diabetes, and its supplement list calls for genuine care rather than a quick skim. Start with the four major-rated entries: alcohol and the herb Siberian cocklebur can each stress the liver, a serious concern with rosiglitazone on board, while activated charcoal can soak up…”

Reviewed by 2 · Jul 18, 2026

Open the Metformin, Rosiglitazone 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 Metformin, Rosiglitazone 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 Metformin, Rosiglitazone 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%

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

29 days ago today
Medication Metformin, Rosiglitazone
Steady interest

#1,697 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
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 Metformin, Rosiglitazone, 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 Metformin, Rosiglitazone supplement interactions › Every supplement checked against Metformin, Rosiglitazone, ranked by severity 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 Metformin, Rosiglitazone Together: Common Questions

Can you take Phellodendron with Metformin, Rosiglitazone?
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 Metformin, Rosiglitazone?
Metformin, Rosiglitazone 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 Metformin, Rosiglitazone 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 Metformin, Rosiglitazone 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.