Drug & supplement interaction

Fennel + Drospirenone, Ethinyl Estradiol

Drospirenone, Ethinyl Estradiol brand names: Yasmin, Gianvi, Angeliq.

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

Drospirenone, Ethinyl Estradiol falls into 3 drug categories that Fennel can interact with; the most serious is rated moderate. Theoretically, taking large amounts of fennel might decrease the effects of contraceptive drugs due to competition for estrogen receptors.

Read the full interaction report
SeverityModerate
LikelihoodPossible
Interactions3
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Fennel and Drospirenone, Ethinyl Estradiol

These two interact in 3 distinct ways. Each one is explained separately below.

Why Are There 3 Interactions?

Fennel interacts with whole categories of medication. Drospirenone, Ethinyl Estradiol falls into 3 of those categories, so it can interact with Fennel in 3 different ways. We’ve listed each one below — your overall risk is driven by the most serious of them (Moderate).

Moderate

CONTRACEPTIVE DRUGS

1 of 3

Why this applies to Drospirenone, Ethinyl Estradiol

Drospirenone, Ethinyl Estradiol falls under CONTRACEPTIVE DRUGS — the group Fennel interacts with.

Theoretically, taking large amounts of fennel might decrease the effects of contraceptive drugs due to competition for estrogen receptors.

Some constituents of fennel have estrogenic activity.
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: your pill, Yasmin (drospirenone with ethinyl estradiol), works by delivering steady hormones that prevent ovulation. Fennel naturally contains plant compounds that act a little like estrogen. The concern on file is mostly theoretical, but the idea is that large amounts of fennel might compete at estrogen receptors and, in theory, slightly blunt how your birth control works.

To be clear, this is a low-level, lab-based concern, not something proven in real people. Normal cooking and seasoning with fennel is very unlikely to matter. If you're considering concentrated fennel supplements or fennel essential oil, just run it by your pharmacist or doctor first, since reliable contraception is too important to gamble on.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Leung AY, Foster S. Encyclopedia of Common Natural Ingredients Used in Food, Drugs and Cosmetics. 2nd ed. New York, NY: John Wiley & Sons, 1996.
Moderate

CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES

2 of 3

Drospirenone, Ethinyl Estradiol also falls under CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES.

Theoretically, fennel might increase levels of drugs metabolized by CYP3A4.

In vitro research suggests that fennel inhibits CYP3A4 enzyme activity. This effect has not been reported in humans.
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

Your birth control pill (Yasmin, Gianvi, and similar) is partly cleared by a liver enzyme called CYP3A4. In a lab dish, fennel seemed to slow that enzyme down. If that happened in real life, the hormones in your pill could clear a bit more slowly and add up, which in theory might mean more of the usual side effects like nausea, breast tenderness, headaches, or spotting.

Here's the honest part: this is only test-tube data and has not been seen in actual people. Enjoying fennel as a food or spice is very unlikely to matter. Concentrated fennel supplements or the essential oil are less predictable, so just run those by your pharmacist or doctor before starting them. Don't change how you take your pill on your own.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Subehan, Usia, T., Iwata, H., Kadota, S., and Tezuka, Y. Mechanism-based inhibition of CYP3A4 and CYP2D6 by Indonesian medicinal plants. J Ethnopharmacol. 5-24-2006;105(3):449-455. PubMed
  2. Subehan, Zaidi, S. F., Kadota, S., and Tezuka, Y. Inhibition on human liver cytochrome P450 3A4 by constituents of fennel (Foeniculum vulgare): identification and characterization of a mechanism-based inactivator. J Agric.Food Chem. 12-12-2007;55(25):101 PubMed
Moderate

ESTROGENS

3 of 3

Drospirenone, Ethinyl Estradiol also falls under ESTROGENS.

Theoretically, taking large amounts of fennel might interfere with hormone replacement therapy due to competition for estrogen receptors.

Some constituents of fennel have estrogenic activity.
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 thing about fennel and a birth control pill like Yasmin or Gianvi: fennel carries some plant compounds that can act a little like estrogen in the body. In theory, very large amounts could nudge in on the same estrogen receptors your pill's ethinyl estradiol works on. This idea comes only from lab pharmacology, not from real-world studies showing problems in people, so I don't want you to lose sleep over it.

Using fennel as a food or spice is very unlikely to matter. The bigger question marks are with concentrated fennel supplements or the essential oil. Since this is birth control, where consistent hormone levels keep it reliable, I'd just run any concentrated fennel product past your pharmacist or doctor before starting it.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Leung AY, Foster S. Encyclopedia of Common Natural Ingredients Used in Food, Drugs and Cosmetics. 2nd ed. New York, NY: John Wiley & Sons, 1996.

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

Fennel Also Interacts With Other Medications

Fennel has 739 moderate known drug interactions in our database — the Drospirenone, Ethinyl Estradiol one above is among them. If you take anything else, check it against the full list below.

Moderate 739 No known interaction 2,091 (incl. Drospirenone, Ethinyl Estradiol)
Taking anything else?

Check Another of Your Medications Against Fennel

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

From our Q&A

Questions About Fennel or Drospirenone, Ethinyl Estradiol

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

This page covers Fennel only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Drospirenone, Ethinyl Estradiol page lists 245 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Beer (major), Grapefruit (major), Siberian Cocklebur (major) and St. John's Wort (major).

By severity: 6 major · 200 moderate · 39 minor.

From our pharmacist’s overview on the Drospirenone, Ethinyl Estradiol page

“Yasmin and similar drospirenone plus ethinyl estradiol pills only prevent pregnancy while hormone levels stay where they should, so read this list with real care, starting with the six entries rated major out of 245 on file. St.”

Reviewed by 2 · Jul 18, 2026

Open the Drospirenone, Ethinyl Estradiol interaction page

One more smart check

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

We hold 2,219 real supplement products containing Fennel, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Fennel. Your product may carry other ingredients that interact with Drospirenone, Ethinyl Estradiol too, on top of Fennel — 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 Fennel and Drospirenone, Ethinyl Estradiol 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 Fennel
Top 10%

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

29 days ago today
Medication Drospirenone, Ethinyl Estradiol
Top 25%

#409 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 Fennel

What is Fennel?

Fennel
  • Digestive upset and bloating
  • Infant colic
  • Menstrual cramps
  • Cough and respiratory complaints
  • Breast milk support (traditional)

Fennel is a Mediterranean herb widely used as a food and spice, and traditionally taken for digestive complaints, colic, and menstrual cramps. Some small studies suggest possible benefit for certain stomach and menstrual symptoms, but the evidence is limited. It is generally well tolerated in food amounts, but concentrated supplements and the essential oil should be used with caution and after checking with your pharmacist or doctor.

Read the full Fennel monograph & all interactions
Keep checking

Other Drugs & Fennel

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

0Major
739Moderate
0Minor
2,090No known interaction
739 Moderate 2,090 No interaction
Moderate

739 interactions

Showing 60 of 739 moderate interactions — see all 739 on the Fennel page.

No interaction 2,090 drugs checked — show the list

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

Showing the 60 most looked-up of 2,090 medications checked with no known interaction — see the full Fennel list.

See the full Fennel interactions page
See every supplement checked against Drospirenone, Ethinyl Estradiol, 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
Fennel monograph › Uses, safety, and every drug interaction in one place Drospirenone, Ethinyl Estradiol supplement interactions › Every supplement checked against Drospirenone, Ethinyl Estradiol, 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 Fennel and Drospirenone, Ethinyl Estradiol Together: Common Questions

Can you take Fennel with Drospirenone, Ethinyl Estradiol?
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.
Why are there 3 interactions listed for Fennel and Drospirenone, Ethinyl Estradiol?
Drospirenone, Ethinyl Estradiol belongs to more than one drug category, and Fennel interacts with each of those categories a little differently. We list every one so nothing is missed — your overall risk is driven by the most serious of them.
How serious is the Fennel and Drospirenone, Ethinyl Estradiol 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 Drospirenone, Ethinyl Estradiol and Fennel?

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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.