Drug & supplement interaction

Hops + Letrozole

Letrozole brand name: Femara.

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

Hops has a minor interaction with Letrozole. Theoretically, hops extract might alter metabolism of CYP3A4 substrates; however, this effect may not be clinically significant.

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

Hops and Letrozole

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

Minor

CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES

Why this applies to Letrozole

Letrozole falls under CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES — the group Hops interacts with.

Theoretically, hops extract might alter metabolism of CYP3A4 substrates; however, this effect may not be clinically significant.
Animal research suggests that specific constituents of hops, called lupulones, can induce hepatic CYP3A4 enzyme activity. However, a pharmacokinetic study in healthy postmenopausal patients with normal metabolism shows that taking a standardized extract of spent hops containing prenylated phenols, as 59.5 mg twice daily for 2 weeks, decreases the concentration of alprazolam, a CYP3A4 probe substrate, by 7.6%. This reduction is unlikely to be clinically relevant.
Severity Minor 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 Letrozole (Femara): your liver clears it partly through an enzyme called CYP3A4. Some lab and animal studies hint that compounds in hops might speed that enzyme up a bit, which in theory could clear letrozole slightly faster and make it a touch less effective at lowering estrogen. Letrozole isn't a prodrug, so faster clearing would mean weaker effect, not stronger.

The good news is this concern is very theoretical. A human study found hops changed levels of a similar drug by only about 8%, which is too small to matter. I wouldn't lose sleep over it, but since letrozole treats breast cancer, it's worth mentioning any hops supplement to your oncologist or pharmacist just to be safe.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Mannering, G. J., Shoeman, J. A., and Deloria, L. B. Identification of the antibiotic hops component, colupulone, as an inducer of hepatic cytochrome P-4503A in the mouse. Drug Metab Dispos 1992;20(2):142-147. DOI
  2. van Breemen RB, Chen L, Tonsing-Carter A, et al. Pharmacokinetic Interactions of a Hop Dietary Supplement with Drug Metabolism in Perimenopausal and Postmenopausal Women. J Agric Food Chem. 2020;68(18):5212-5220. 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

Hops Also Interacts With Other Medications

Hops has 289 moderate, 573 minor known drug interactions in our database — the Letrozole one above is one of them. If you take anything else, check it against the full list below.

Moderate 289 Minor 573 No known interaction 1,968 (incl. Letrozole)
Taking anything else?

Check Another of Your Medications Against Hops

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

From our Q&A

Questions About Hops or Letrozole

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

This page covers Hops only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Letrozole page lists 142 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Grapefruit (major), St. John's Wort (major), 7-methoxyflavone (moderate) and Acacia Rigidula (moderate).

By severity: 3 major · 99 moderate · 40 minor.

From our pharmacist’s overview on the Letrozole page

“Letrozole (Femara) is prescribed to keep hormone-driven breast cancer from returning, so a supplement that shifts its blood level can quietly undercut treatment. Give this list of 142 ingredients genuine respect, and learn the three major entries first.”

Reviewed by 2 · Jul 18, 2026

Open the Letrozole interaction page

One more smart check

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

We hold 1,325 real supplement products containing Hops, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Hops. Your product may carry other ingredients that interact with Letrozole too, on top of Hops — 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 Hops and Letrozole 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 Hops
Top 25%

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

29 days ago today
Medication Letrozole
Top 5%

#51 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 Hops

What is Hops?

Hops
  • Sleep problems and insomnia
  • Anxiety and restlessness
  • Menopausal symptoms
  • Mild digestive complaints
  • Flavoring in beer and food

Hops are most often used for sleep and mild anxiety, frequently combined with valerian, but the human evidence is limited and not very strong. They are generally well tolerated when used short-term, though they may cause drowsiness, and should be avoided during pregnancy and breastfeeding because their safety is unknown.

Read the full Hops monograph & all interactions
Medication

About Letrozole

What Is Letrozole Used For?

Brand name: Femara

Letrozole (brand name Femara) is used to treat breast cancer in postmenopausal women whose tumors are driven by estrogen. It is used in three settings: as adjuvant (after-surgery) treatment for hormone receptor positive early breast cancer; as extended adjuvant treatment for women who have already completed about five years of tamoxifen therapy; and as first- or second-line treatment for locally advanced or metastatic (spread) breast cancer.

Femara is specifically indicated for first-line treatment of hormone receptor positive or receptor-unknown locally advanced or metastatic breast cancer, and for advanced breast cancer in women whose disease has progressed after antiestrogen therapy.

See full Letrozole drug information
Keep checking

Other Drugs & Hops

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

0Major
289Moderate
573Minor
1,967No known interaction
289 Moderate 573 Minor 1,967 No interaction
Moderate

289 interactions

Showing 60 of 289 moderate interactions — see all 289 on the Hops page.

Minor

573 interactions

Showing 60 of 573 minor interactions — see all 573 on the Hops page.

No interaction 1,967 drugs checked — show the list

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

Showing the 60 most looked-up of 1,967 medications checked with no known interaction — see the full Hops list.

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

Can you take Hops with Letrozole?
There is only a minor interaction, which is usually not serious. Read the full details on this page and confirm with your pharmacist before combining them.
How serious is the Hops and Letrozole interaction?
We rate it Minor. This interaction is generally not clinically significant, but it remains worth noting and discussing with your pharmacist.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Still Have a Question About Letrozole and Hops?

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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.