Drug & supplement interaction

Ashwagandha + Fluorouracil (IV)

Fluorouracil (IV) brand name: Fluorouracil.

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

Ashwagandha has a moderate interaction with Fluorouracil (IV). Theoretically, taking ashwagandha might decrease the effects of immunosuppressants.

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

Ashwagandha 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 Ashwagandha interacts with.

Theoretically, taking ashwagandha might decrease the effects of immunosuppressants.
Ashwagandha has demonstrated immunostimulant effects in humans. Animal research has shown that ashwagandha can attenuate the immunosuppression caused by cyclophosphamide.
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, often called 5-FU. This is a chemotherapy drug your oncology team gives through an IV, and part of how it works against cancer is by dampening fast-growing cells, including some immune cells. Ashwagandha, on the other hand, has shown signs in lab and animal studies that it can stimulate the immune system. So in theory, it could work against what your treatment is trying to do.

I want to be honest about the evidence here: this concern is mostly theoretical, based on test-tube and animal work, not human studies with 5-FU. Still, because chemotherapy is serious business and timing matters, I'd never add ashwagandha during treatment without first clearing it with your oncologist or pharmacist.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Upton R, ed. Ashwagandha Root (Withania somnifera): Analytical, quality control, and therapuetic monograph. Santa Cruz, CA: American Herbal Pharmacopoeia 2000:1-25.
  2. Davis L, Kuttan G. Effect of Withania somnifera on cyclophosphamide-induced urotoxicity. Cancer Lett 2000;148:9-17. PubMed
  3. Davis L, Kuttan G. Suppressive effect of cyclophosphamide-induced toxicity by Withania somnifera extract in mice. J Ethnopharmacol 1998;62:209-14. PubMed
  4. Mishra LC, Singh BB, Dagenais S. Scientific basis for the therapeutic use of Withania somnifera (ashwagandha): a review. Altern Med Rev 2000;5:334-46. DOI
  5. Tharakan A, Shukla H, Benny IR, Tharakan M, George L, Koshy S. Immunomodulatory Effect of Withania somnifera (Ashwagandha) Extract-A Randomized, Double-Blind, Placebo Controlled Trial with an Open Label Extension on Healthy Participants. J Clin Med 2021;1 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

Ashwagandha Also Interacts With Other Medications

Ashwagandha has 915 moderate, 456 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.

Moderate 915 Minor 456 No known interaction 1,459 (incl. Fluorouracil (IV))
Taking anything else?

Check Another of Your Medications Against Ashwagandha

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

From our Q&A

Questions About Ashwagandha 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 Ashwagandha 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 Ashwagandha 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 Astragalus (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 Ashwagandha as Part of a Dietary Supplement Product? Check It for Interactions

We hold 4,964 real supplement products containing Ashwagandha, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Ashwagandha. Your product may carry other ingredients that interact with Fluorouracil (IV) too, on top of Ashwagandha — 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 Ashwagandha 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 Ashwagandha
Top 5%

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

29 days ago today
Medication Fluorouracil (IV)
Steady interest

#2,289 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 Ashwagandha

What is Ashwagandha?

Ashwagandha
  • Stress and anxiety
  • Sleep problems
  • Fatigue and low energy
  • Athletic performance
  • General well-being (adaptogen)

Ashwagandha is an Ayurvedic herb most often taken to help with stress, anxiety, and sleep, and some small studies suggest it may help, though the evidence is still limited. It is generally well tolerated for short-term use in healthy adults, but it should be avoided in pregnancy and used cautiously by people with thyroid or liver problems. Talk with your pharmacist or doctor before starting it.

Read the full Ashwagandha monograph & all interactions
Keep checking

Other Drugs & Ashwagandha

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

0Major
915Moderate
456Minor
1,458No known interaction
915 Moderate 456 Minor 1,458 No interaction
Moderate

915 interactions

Showing 60 of 915 moderate interactions — see all 915 on the Ashwagandha page.

Minor

456 interactions

Showing 60 of 456 minor interactions — see all 456 on the Ashwagandha page.

No interaction 1,458 drugs checked — show the list

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

Showing the 60 most looked-up of 1,458 medications checked with no known interaction — see the full Ashwagandha list.

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

Can you take Ashwagandha 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 Ashwagandha 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 Ashwagandha?

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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.