Drug & supplement interaction

Green Tea + Fluorouracil (IV)

Fluorouracil (IV) brand name: Fluorouracil.

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

Green Tea has a moderate interaction with Fluorouracil (IV). Theoretically, high doses of green tea might increase the effects and side effects of 5-fluorouracil.

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

Green Tea and Fluorouracil (IV)

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

Moderate

5-FLUOROURACIL

Why this applies to Fluorouracil (IV)

Fluorouracil (IV) falls under 5-FLUOROURACIL — the group Green Tea interacts with.

Theoretically, high doses of green tea might increase the effects and side effects of 5-fluorouracil.
Animal research shows that taking green tea in amounts equivalent to about 6 cups daily in humans for 4 weeks prior to receiving a single injection of 5-fluorouracil increases the maximum plasma levels of 5-fluorouracil by about 2.5-fold and the area under the curve by 425%.
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 short version if you're getting fluorouracil (an IV chemotherapy drug, often called 5-FU). The concern is that concentrated green tea, in large amounts, might raise the level of fluorouracil in your blood. In animal studies, green tea roughly equal to 6 cups a day for several weeks pushed 5-FU blood levels up quite a bit. More drug floating around can mean stronger effects and more side effects, like mouth sores, diarrhea, nausea, and bigger drops in blood counts.

I want to be honest about the evidence though: this is theoretical and comes from lab and animal work, not human trials. An occasional cup of tea is unlikely to be the issue. Still, since chemo dosing is so precise, please check with your oncology pharmacist or doctor before using any green tea supplements or drinking large amounts.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Qiao J, Gu C, Shang W, et al. Effect of green tea on pharmacokinetics of 5-fluorouracil in rats and pharmacodynamics in human cell lines in vitro. Food Chem Toxicol. 2011;49(6):1410-5. 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

Green Tea Also Interacts With Other Medications

Green Tea has 13 major, 904 moderate, 375 minor known drug interactions in our database — the Fluorouracil (IV) one above is one of them. If you take anything else, check it against the full list below.

Major 13 Moderate 904 Minor 375 No known interaction 1,538 (incl. Fluorouracil (IV))
Taking anything else?

Check Another of Your Medications Against Green Tea

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

From our Q&A

Questions About Green Tea or Fluorouracil (IV)

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Green Tea or Fluorouracil (IV), 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 Fluorouracil (IV)

This page covers Green Tea only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Fluorouracil (IV) page lists 59 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Active Hexose Correlated Compound (ahcc) (moderate), Alfalfa (moderate), American Ginseng (moderate), Andrographis (moderate) and Ashwagandha (moderate).

By severity: 58 moderate · 1 minor.

From our pharmacist’s overview on the Fluorouracil (IV) page

“Fluorouracil is an IV chemotherapy medicine, and the supplement list attached to it is manageable for most people once you see the single thread running through it. Nearly all 59 entries are herbs and extracts believed to stimulate the immune system, ashwagandha, astragalus, and medicinal mushroom products among them, and the concern i…”

Reviewed by 2 · Jul 18, 2026

Open the Fluorouracil (IV) interaction page

One more smart check

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

We hold 9,084 real supplement products containing Green Tea, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Green Tea. Your product may carry other ingredients that interact with Fluorouracil (IV) too, on top of Green Tea — 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 Green Tea and Fluorouracil (IV) 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 Green Tea
Top 5%

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

29 days ago today
Medication Fluorouracil (IV)
Steady interest

#1,548 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 Green Tea

What is Green Tea?

Green Tea
  • Antioxidant support
  • Weight loss
  • Heart health
  • Mental alertness
  • Cancer risk reduction

Green tea is a popular beverage rich in antioxidants called catechins, and drinking it in normal amounts is considered safe for most people. Concentrated green tea extracts are a different story—they may help modestly with weight or heart health for some, but high doses have been linked to rare liver problems. Talk to your pharmacist or doctor before taking green tea supplements, especially if you have liver concerns or are pregnant.

Read the full Green Tea monograph & all interactions
Keep checking

Other Drugs & Green Tea

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

13Major
904Moderate
375Minor
1,537No known interaction
13 Major 904 Moderate 375 Minor 1,537 No interaction
Major

13 interactions

Moderate

904 interactions

Showing 60 of 904 moderate interactions — see all 904 on the Green Tea page.

Minor

375 interactions

Showing 60 of 375 minor interactions — see all 375 on the Green Tea page.

No interaction 1,537 drugs checked — show the list

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

Showing the 60 most looked-up of 1,537 medications checked with no known interaction — see the full Green Tea list.

See the full Green Tea interactions page
See every supplement checked against Fluorouracil (IV), 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
Green Tea monograph › Uses, safety, and every drug interaction in one place Fluorouracil (IV) supplement interactions › Every supplement checked against Fluorouracil (IV), 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 Green Tea and Fluorouracil (IV) Together: Common Questions

Can you take Green Tea with Fluorouracil (IV)?
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 Green Tea and Fluorouracil (IV) 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 Fluorouracil (IV) and Green Tea?

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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.