Drug & supplement interaction

Ginkgo + Tamoxifen Citrate

Tamoxifen Citrate brand names: Nolvadex, Soltamox.

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

Tamoxifen Citrate falls into 3 drug categories that Ginkgo can interact with; the most serious is rated moderate. Theoretically, ginkgo might increase 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

Ginkgo and Tamoxifen Citrate

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

Why Are There 3 Interactions?

Ginkgo interacts with whole categories of medication. Tamoxifen Citrate falls into 3 of those categories, so it can interact with Ginkgo 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 Tamoxifen Citrate

Tamoxifen Citrate falls under CYTOCHROME P450 2C9 (CYP2C9) SUBSTRATES — the group Ginkgo interacts with.

Theoretically, ginkgo might increase levels of drugs metabolized by CYP2C9.
In vitro, a specific standardized extract of ginkgo leaf (EGb 761) inhibits CYP2C9 activity . The terpenoid (ginkgolides) and flavonoid (quercetin, kaempferol, etc.) constituents seem to be responsible for this effect. Most ginkgo extracts contain some amount of these constituents. Therefore, other ginkgo leaf extracts might also inhibit the CYP2C9 enzyme. However, clinical research suggests that ginkgo might not have a significant effect on CYP2C9 in humans. Ginkgo does not seem to significantly affect the pharmacokinetics of CYP2C9 substrates diclofenac or tolbutamide.
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 wrinkle with tamoxifen: it's actually a prodrug. Your body has to convert it into its active form (called endoxifen) for it to fight breast cancer effectively. While the enzyme CYP2D6 does most of that heavy lifting, CYP2C9 also plays a part, and the lab data suggests ginkgo might slow CYP2C9 down a little.

The honest truth is this concern is mostly theoretical. It comes from test-tube studies, and in actual human research ginkgo didn't meaningfully change how other CYP2C9 drugs behaved. So a big swing in your tamoxifen levels is unlikely. Still, tamoxifen is too important to leave to guesswork, and ginkgo can also thin the blood. Please run it by your oncologist or pharmacist before adding ginkgo, so you keep getting the full protective benefit.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Yale SH, Glurich I. Analysis of the inhibitory potential of Ginkgo biloba, Echinacea purpurea, and Serenoa repens on the metabolic activity of cytochrome P450 3A4, 2D6, and 2C9. J Altern Complement Med 2005;11:433-9.
  2. Gaudineau C, Beckerman R, Welbourn S, Auclair K. Inhibition of human P450 enzymes by multiple constituents of the Ginkgo biloba extract. Biochem Biophys Res Comm 2004;318:1072–8. PubMed
  3. Mohutsky MA, Anderson GD, Miller JW, Elmer GW. Ginkgo biloba: evaluation of CYP2C9 drug interactions in vitro and in vivo. Am J Ther 2006;13:24-31. PubMed
Moderate

CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES

2 of 3

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

Theoretically, ginkgo might decrease levels of drugs metabolized by CYP3A4.
There is conflicting evidence about whether ginkgo induces or inhibits CYP3A4. Ginkgo does not appear to affect hepatic CYP3A4. However, it is not known if ginkgo affects intestinal CYP3A4. Preliminary clinical research suggests that taking ginkgo does not significantly affect levels of donepezil, lopinavir, or ritonavir, which are all CYP3A4 substrates. Other clinical research also suggests ginkgo does not significantly affect CYP3A4 activity. However, there are two case reports of decreased efavirenz concentrations and increased viral load in patients taking ginkgo. It is suspected that terpenoids from the ginkgo extract reduced drug levels by inducing cytochrome P450 3A4 (CYP3A4).
Severity Moderate Likelihood Possible Evidence B

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 a wrinkle worth knowing: tamoxifen is actually a prodrug. Your body has to convert it into its active forms (mainly something called endoxifen) before it can do its job of fighting breast cancer. The main enzyme that turns it on is CYP2D6, with some help from CYP3A4. The interaction on file is about ginkgo possibly nudging CYP3A4 activity, but honestly the evidence here is shaky and conflicting. In most studies, ginkgo didn't meaningfully change CYP3A4-cleared drugs.

So I wouldn't lose sleep over this one, but I would still loop in your oncology team. Tamoxifen is too important to leave anything to chance, and ginkgo can also thin the blood a bit. A quick check with your pharmacist or doctor before combining them is the smart move.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Gurley BJ, Gardner SF, Hubbard MA. Clinical assessment of potential cytochrome P450-mediated herb-drug interactions. AAPS Ann Mtg & Expo Indianapolis, IN: 2000; Oct 29 - Nov 2:presentation #3460.
  2. Galluzzi S, Zanetti O, Binetti G, et al. Coma in a patient with Alzheimer's disease taking low dose trazodone and Ginkgo biloba. J Neurol Neurosurg Psychiatry 2000;68:679-80. DOI
  3. 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
  4. Gurley BJ, Gardner SF, Hubbard MA, et al. Cytochrome P450 phenotypic ratios for predicting herb-drug interactions in humans. Clin Pharmacol Ther 2002;72:276-87.. PubMed
  5. Yale SH, Glurich I. Analysis of the inhibitory potential of Ginkgo biloba, Echinacea purpurea, and Serenoa repens on the metabolic activity of cytochrome P450 3A4, 2D6, and 2C9. J Altern Complement Med 2005;11:433-9.
  6. Yasui-Furukori N, Furukori H, Kaneda A, et al. The effects of Ginkgo biloba extracts on the pharmacokinetics and pharmacodynamics of donepezil. J Clin Pharmacol 2004;44:538-42.
  7. Markowitz JS, Donovan JL, Lindsay DeVane C, et al. Multiple-dose administration of Ginkgo biloba did not affect cytochrome P-450 2D6 or 3A4 activity in normal volunteers. J Clin Psychopharmacol 2003;23:576-81. PubMed
  8. Wiegman DJ, Brinkman K, Franssen EJ. Interaction of Ginkgo biloba with efavirenz. AIDS 2009;23:1184-5. PubMed
  9. Naccarato M, Yoong D, Gough K. A potential drug-herbal interaction between Ginkgo biloba and efavirenz. J Int Assoc Physicians AIDS Care (Chic). 2012;11(2):98-100. doi: 10.1177/1545109711435364. Epub 2012 Feb 9.
  10. Robertson, S. M., Davey, R. T., Voell, J., Formentini, E., Alfaro, R. M., and Penzak, S. R. Effect of Ginkgo biloba extract on lopinavir, midazolam and fexofenadine pharmacokinetics in healthy subjects. Curr Med Res Opin 2008;24(2):591-599. PubMed
  11. Penzak, S. R., Busse, K. H., Robertson, S. M., Formentini, E., Alfaro, R. M., and Davey, R. T., Jr. Limitations of using a single postdose midazolam concentration to predict CYP3A-mediated drug interactions. J Clin Pharmacol 2008;48(6):671-680. PubMed
  12. Jalloh MA, Gregory PJ, Hein D, et al. Dietary supplement interactions with antiretrovirals: a systematic review. Int J STD AIDS. 2017 Jan;28(1):4-15. PubMed
  13. Bai J, Zhang C. Metabolic interaction between biflavonoids in Ginkgo biloba leaves and tacrolimus. Biopharm Drug Dispos 2023;44(2):157-164.
Moderate

P-GLYCOPROTEIN SUBSTRATES

3 of 3

Tamoxifen Citrate also falls under P-GLYCOPROTEIN SUBSTRATES.

Theoretically, taking ginkgo with P-glycoprotein substrates might increase the levels and adverse effects of these substrates.
A small clinical study in healthy volunteers shows that using ginkgo leaf extract 120 mg orally three times daily for 14 days can increase levels of the P-glycoprotein substrate, talinolol, by 36% in healthy male individuals. However, single doses of ginkgo do not have the same effect.
Severity Moderate Likelihood Possible Evidence B

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 tamoxifen and ginkgo. Tamoxifen is moved around your body partly by a pump called P-glycoprotein. Ginkgo can slow that pump down a little, so in theory tamoxifen levels could creep up. The data behind this is on the soft side: it comes from a small study using a different drug (talinolol), where regular daily ginkgo (not a single dose) nudged that drug's levels up by about a third.

If tamoxifen built up, you might notice more of its usual effects, like hot flashes, nausea, or fatigue. This is mostly theoretical, but tamoxifen matters too much to gamble with. Please don't start or stop anything on your own. Just loop in your oncologist or pharmacist before adding ginkgo.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Fan, L., Tao, G. Y., Wang, G., Chen, Y., Zhang, W., He, Y. J., Li, Q., Lei, H. P., Jiang, F., Hu, D. L., Huang, Y. F., and Zhou, H. H. Effects of Ginkgo biloba extract ingestion on the pharmacokinetics of talinolol in healthy Chinese volunteers. Ann Phar 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

Ginkgo Also Interacts With Other Medications

Ginkgo has 1 major, 1,264 moderate known drug interactions in our database — the Tamoxifen Citrate one above is among them. If you take anything else, check it against the full list below.

Major 1 Moderate 1,264 No known interaction 1,565 (incl. Tamoxifen Citrate)
Taking anything else?

Check Another of Your Medications Against Ginkgo

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

From our Q&A

Questions About Ginkgo or Tamoxifen Citrate

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

This page covers Ginkgo only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Tamoxifen Citrate page lists 210 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), American Hellebore (major), Arsenic (major), Beer (major) and Cesium (major).

By severity: 11 major · 166 moderate · 33 minor.

From our pharmacist’s overview on the Tamoxifen Citrate page

“Tamoxifen (Nolvadex, Soltamox) often stands between a breast cancer patient and a recurrence, so the stakes on this page run higher than usual. Eleven of the 210 supplements and herbs on file carry a major rating, and those eleven deserve your attention ahead of everything else.”

Reviewed by 2 · Jul 18, 2026

Open the Tamoxifen Citrate interaction page

One more smart check

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

We hold 4,399 real supplement products containing Ginkgo, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Ginkgo. Your product may carry other ingredients that interact with Tamoxifen Citrate too, on top of Ginkgo — 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 Ginkgo and Tamoxifen Citrate 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 Ginkgo
Top 5%

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

29 days ago today
Medication Tamoxifen Citrate
Top 5%

#98 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 Ginkgo

What is Ginkgo?

Ginkgo
  • Memory and cognitive support
  • Age-related mental decline
  • Circulation problems
  • Tinnitus (ringing in the ears)
  • Dizziness or vertigo

Ginkgo is one of the world's most popular herbal supplements, mostly taken to support memory and circulation. The evidence for these uses is mixed and generally weak, and it is not proven to prevent memory loss or dementia. It is usually well tolerated in healthy adults, but it can thin the blood, so talk to your pharmacist or doctor before using it.

Read the full Ginkgo monograph & all interactions
Medication

About Tamoxifen

What Is Tamoxifen Used For?

Brand names: Nolvadex, Soltamox

Tamoxifen is used to treat estrogen receptor-positive metastatic breast cancer in both women and men, and as follow-up (adjuvant) therapy after surgery for early-stage breast cancer in women. It also reduces the occurrence of cancer in the opposite breast when used as adjuvant therapy.

In women with ductal carcinoma in situ (DCIS — an early, non-invasive breast change) following surgery and radiation, tamoxifen lowers the risk of developing invasive breast cancer. It is also approved to reduce the risk of breast cancer in women who are at high risk but have not yet been diagnosed. Both Tamoxifen Citrate tablets and Soltamox oral solution share these indications.

See full Tamoxifen drug information
Keep checking

Other Drugs & Ginkgo

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

1Major
1,264Moderate
0Minor
1,564No known interaction
1 Major 1,264 Moderate 1,564 No interaction
Major

1 interaction

Moderate

1,264 interactions

Showing 60 of 1,264 moderate interactions — see all 1,264 on the Ginkgo page.

No interaction 1,564 drugs checked — show the list

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

Showing the 60 most looked-up of 1,564 medications checked with no known interaction — see the full Ginkgo list.

See the full Ginkgo interactions page
See every supplement checked against Tamoxifen Citrate, 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
Ginkgo monograph › Uses, safety, and every drug interaction in one place Tamoxifen Citrate supplement interactions › Every supplement checked against Tamoxifen Citrate, ranked by severity Tamoxifen 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 Ginkgo and Tamoxifen Citrate Together: Common Questions

Can you take Ginkgo with Tamoxifen Citrate?
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 Ginkgo and Tamoxifen Citrate?
Tamoxifen Citrate belongs to more than one drug category, and Ginkgo 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 Ginkgo and Tamoxifen Citrate 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 Tamoxifen Citrate and Ginkgo?

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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.