Drug & supplement interaction

European Mistletoe + Fluorouracil (IV)

Fluorouracil (IV) brand name: Fluorouracil.

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

European Mistletoe has a moderate interaction with Fluorouracil (IV). Theoretically, European mistletoe might decrease the effectiveness of immunosuppressants.

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

European Mistletoe and Fluorouracil (IV)

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

Moderate

IMMUNOSUPPRESSANTS

Why this applies to Fluorouracil (IV)

Fluorouracil (IV) falls under IMMUNOSUPPRESSANTS — the group European Mistletoe interacts with.

Theoretically, European mistletoe might decrease the effectiveness of immunosuppressants.
Clinical and in vitro studies suggest that European mistletoe might have immunostimulant effects.
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 for fluorouracil (5-FU): this chemo drug works partly by tamping down fast-growing cells, and your immune system is part of that picture. European mistletoe, on the other hand, is thought to rev up the immune system. In theory, those two pull in opposite directions, and mistletoe could blunt some of the effects you and your oncologist are counting on from 5-FU.

I want to be honest about the strength here: this concern comes from lab and animal work, not solid human studies, so it's more of a caution than a proven problem. Still, with cancer treatment there's no room to guess. Please don't add any mistletoe product on your own, and loop in your oncology team or pharmacist before using it, since some European clinics do supervise it carefully.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Natl Cancer Inst. Mistletoe (PDQ). CancerNet. www.cancernet.nci.nih.gov/cam/mistletoe.htm#7 (Accessed 30 March 2001).
  2. Timoshenko AV, Cherenkevich SN, Gabius HJ. Viscum album agglutinin-induced aggregation of blood cells and the lectin effects on neutrophil function. Biomed Pharmacother 1995;49:153-8.. PubMed
  3. Bussing A, Regnery A, Schweizer K. Effects of Viscum album L. on cyclophosphamide-treated peripheral blood mononuclear cells in vitro: sister chromatid exchanges and activation/proliferation marker expression. Cancer Lett 1995;94:199-205.. PubMed
  4. Chernyshov VP, Omelchenko LI, Heusser P, and et al. Immunomodulatory actions of Viscum album (Iscador) in children with recurrent respiratory disease as a result of the Chernobyl nuclear accident. Complementary Therapies in Medicine 1997;5(3):141-146. DOI
  5. Chernyshov, V. P., Heusser, P., Omelchenko, L. I., Chernyshova, L. I., Vodyanik, M. A., Vykhovanets, E. V., Galazyuk, L. V., Pochinok, T. V., Gaiday, N. V., Gumenyuk, M. E., Zelinsky, G. M., Schaefermeyer, H., and Schaefermeyer, G. Immunomodulatory and cl
  6. Cogo E, Elsayed M, Bhardwaj S, et al. Mistletoe Extracts during the Oncological Perioperative Period: A Systematic Review and Meta-Analysis of Human Randomized Controlled Trials. Curr Oncol 2023;30(9):8196-8219. 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

European Mistletoe Also Interacts With Other Medications

European Mistletoe has 292 moderate 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.

Moderate 292 No known interaction 2,538 (incl. Fluorouracil (IV))
Taking anything else?

Check Another of Your Medications Against European Mistletoe

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

Everything else you take

See Every Supplement That Interacts With Fluorouracil (IV)

This page covers European Mistletoe 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 European Mistletoe as Part of a Dietary Supplement Product? Check It for Interactions

We hold 91 real supplement products containing European Mistletoe, each one broken down to its full ingredient list — and combination products often carry several ingredients besides European Mistletoe. Your product may carry other ingredients that interact with Fluorouracil (IV) too, on top of European Mistletoe — 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 European Mistletoe 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 European Mistletoe
Top half

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

29 days ago today
Medication Fluorouracil (IV)
Steady interest

#2,750 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 European Mistletoe

What is European Mistletoe?

European Mistletoe
  • Cancer supportive care
  • Immune support
  • High blood pressure
  • Anxiety and stress
  • Inflammation

European mistletoe is a parasitic plant most studied as an injectable extract used alongside conventional cancer care in some European countries, mainly to improve quality of life rather than to cure cancer. The plant is toxic if eaten, and oral or self-treatment can be dangerous, so it should only be used under medical supervision. Talk to your pharmacist or doctor before using any mistletoe product.

Read the full European Mistletoe monograph & all interactions
Keep checking

Other Drugs & European Mistletoe

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

0Major
292Moderate
0Minor
2,537No known interaction
292 Moderate 2,537 No interaction
Moderate

292 interactions

Showing 60 of 292 moderate interactions — see all 292 on the European Mistletoe page.

No interaction 2,537 drugs checked — show the list

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

Showing the 60 most looked-up of 2,537 medications checked with no known interaction — see the full European Mistletoe list.

See the full European Mistletoe 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
European Mistletoe 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 European Mistletoe and Fluorouracil (IV) Together: Common Questions

Can you take European Mistletoe 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 European Mistletoe 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 European Mistletoe?

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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.