Drug & supplement interaction

Limonene + Fluorouracil (IV)

Fluorouracil (IV) brand name: Fluorouracil.

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

Limonene has a moderate interaction with Fluorouracil (IV). There's preliminary evidence that limonene might be a substrate for cytochrome P450 2C9 (CYP2C9).

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

Limonene and Fluorouracil (IV)

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

Moderate

CYTOCHROME P450 2C9 (CYP2C9) INHIBITORS

Why this applies to Fluorouracil (IV)

Fluorouracil (IV) falls under CYTOCHROME P450 2C9 (CYP2C9) INHIBITORS — the group Limonene interacts with.

There's preliminary evidence that limonene might be a substrate for cytochrome P450 2C9 (CYP2C9). So far, this interaction has not been reported in humans. However, watch for side effects in patients taking limonene and CYP2C9 inhibitors. Some CYP2C9 inhibitors include amiodarone (Cordarone), fluconazole (Diflucan), lovastatin (Mevacor), paroxetine (Paxil), zafirlukast (Accolate), and many others.
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 IV fluorouracil (5-FU). The concern on file is actually about the supplement, not your chemo. Limonene appears, based only on lab and animal data, to be broken down partly by an enzyme called CYP2C9. IV fluorouracil can act as a mild blocker of that same enzyme. So the theory is that your chemo could slow limonene's breakdown and let more of the supplement build up, which might mean more limonene-related side effects, not stronger 5-FU.

This has never actually been reported in people, so it's a weak, theoretical flag. Still, fluorouracil is serious chemotherapy, and I'd want nothing added during treatment without your oncology team's okay. Please check with your oncologist or pharmacist before using any limonene supplement.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Crowell PL. Prevention and therapy of cancer by dietary monoterpenes. J Nutr 1999;129:775S-778S. PubMed
  2. Miyazawa M, Shindo M, Shimada T. Metabolism of (+)- and (-)-limonenes to respective carveols and perillyl alcohols by CYP2C9 and CYP2C19 in human liver microsomes. Drug Metab Dispos 2002;30:602-7. 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

Limonene Also Interacts With Other Medications

Limonene has 228 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 228 No known interaction 2,602 (incl. Fluorouracil (IV))
Taking anything else?

Check Another of Your Medications Against Limonene

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

Everything else you take

See Every Supplement That Interacts With Fluorouracil (IV)

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

We hold 89 real supplement products containing Limonene, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Limonene. Your product may carry other ingredients that interact with Fluorouracil (IV) too, on top of Limonene — 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 Limonene 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 Limonene
Steady interest

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

29 days ago today
Medication Fluorouracil (IV)
Steady interest

#1,707 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 Limonene

What is Limonene?

  • Heartburn and acid reflux
  • Digestive upset
  • Stress and mood support
  • Antioxidant support
  • General wellness

Limonene is a natural compound found in the peel of citrus fruits like oranges and lemons, and it is used as a flavoring agent and dietary supplement. People take it for heartburn, digestion, and general wellness, but solid human evidence is limited. It is generally well tolerated in food amounts, but talk with your pharmacist or doctor before using concentrated supplements.

Read the full Limonene monograph & all interactions
Keep checking

Other Drugs & Limonene

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

0Major
228Moderate
0Minor
2,601No known interaction
228 Moderate 2,601 No interaction
Moderate

228 interactions

Showing 60 of 228 moderate interactions — see all 228 on the Limonene page.

No interaction 2,601 drugs checked — show the list

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

Showing the 60 most looked-up of 2,601 medications checked with no known interaction — see the full Limonene list.

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

Can you take Limonene 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 Limonene 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 Limonene?

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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.