Fennel + Ethinyl Estradiol, Norethindrone, Ferrous Fumarate
Ethinyl Estradiol, Norethindrone, Ferrous Fumarate brand names: Estrostep Fe, Loestrin Fe, Microgestin FE, Junel Fe 1.5/30, Loestrin Fe 1.5/30, and others.
Ethinyl Estradiol, Norethindrone, Ferrous Fumarate 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 reportFennel and Ethinyl Estradiol, Norethindrone, Ferrous Fumarate
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. Ethinyl Estradiol, Norethindrone, Ferrous Fumarate 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).
CONTRACEPTIVE DRUGS
1 of 3Why this applies to Ethinyl Estradiol, Norethindrone, Ferrous Fumarate
Ethinyl Estradiol, Norethindrone, Ferrous Fumarate falls under CONTRACEPTIVE DRUGS — the group Fennel interacts with.
Some constituents of fennel have estrogenic activity.
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.
Here's the gist for your birth control pill (the combo of ethinyl estradiol, norethindrone, and a little iron). Fennel contains plant compounds that act faintly like estrogen in the body. In theory, taking large, concentrated fennel supplement doses might compete with your pill's hormones at the same receptors, which could in turn nudge down how reliably the pill prevents pregnancy. There's no separate prodrug step here, so the concern is simply slightly weaker contraceptive coverage.
I want to be honest: this is a theoretical worry based on lab activity, not real cases of failed birth control. Normal food and cooking amounts of fennel are very unlikely to matter. If you're considering a concentrated fennel supplement or the essential oil, just run it by your pharmacist or doctor first.
- Leung AY, Foster S. Encyclopedia of Common Natural Ingredients Used in Food, Drugs and Cosmetics. 2nd ed. New York, NY: John Wiley & Sons, 1996.
CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES
2 of 3Ethinyl Estradiol, Norethindrone, Ferrous Fumarate also falls under CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES.
In vitro research suggests that fennel inhibits CYP3A4 enzyme activity. This effect has not been reported in humans.
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.
Your birth control pill contains ethinyl estradiol and norethindrone, both of which the body partly clears using a liver enzyme called CYP3A4. In test-tube studies, fennel appears to slow this enzyme down a bit. In theory, that could let a little more estrogen and progestin linger in your system, which might mean slightly more of the usual hormone side effects like nausea, breast tenderness, bloating, or spotting.
Here's the honest part: this comes only from lab research, not from real people, so we don't actually know if it matters in everyday life. Cooking with fennel or sipping fennel tea is very unlikely to cause trouble. Concentrated fennel capsules or the essential oil are where I'd be more careful. If you use those regularly, just run it by your pharmacist or doctor first.
- 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
- 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
ESTROGENS
3 of 3Ethinyl Estradiol, Norethindrone, Ferrous Fumarate also falls under ESTROGENS.
Some constituents of fennel have estrogenic activity.
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.
Your pill (the combo in Loestrin Fe, Microgestin Fe, and similar brands) delivers estrogen and progestin to prevent pregnancy. Here's the thing about fennel: some of its plant compounds act a little like estrogen and may nudge their way onto the same receptors your hormones use. In theory, large amounts could compete with your medication's signaling. I want to be honest though, this is a theoretical concern based on how fennel behaves in the lab, not on real cases of women's birth control failing.
Fennel in food, like in cooking or tea, is very unlikely to cause any problem. Concentrated fennel supplements or the essential oil are where I'd pump the brakes. If you're counting on this pill for contraception, please check with your pharmacist or doctor before adding a strong fennel supplement.
- 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.
Clinically significant. Avoid the combination, or use only under close professional supervision.
Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.
Generally not serious. Be aware of it and mention it to your pharmacist.
- 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.
- 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.
Fennel Also Interacts With Other Medications
Fennel has 741 moderate known drug interactions in our database — the Ethinyl Estradiol, Norethindrone, Ferrous Fumarate one above is among them. If you take anything else, check it against the full list below.
Check Another of Your Medications Against Fennel
We haven’t checked that one against Fennel yet — ask our pharmacists directly.
Covers the 2,830 medications we’ve checked against Fennel. Pick one to open its full report.
Questions About Fennel or Ethinyl Estradiol, Norethindrone, Ferrous Fumarate
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 Ethinyl Estradiol, Norethindrone, Ferrous Fumarate, 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.
See Every Supplement That Interacts With Ethinyl Estradiol, Norethindrone, Ferrous Fumarate
This page covers Fennel only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Ethinyl Estradiol, Norethindrone, Ferrous Fumarate page lists 240 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 · 196 moderate · 38 minor.
From our pharmacist’s overview on the Ethinyl Estradiol, Norethindrone, Ferrous Fumarate page
“If you take a birth control pill that combines ethinyl estradiol, norethindrone, and iron (Loestrin Fe, Estrostep Fe, Microgestin Fe), a few supplements can genuinely undermine it, and I want you to know which ones first. Six of the 240 ingredients on file carry a major rating.”
Reviewed by 2 · Jul 18, 2026
Open the Ethinyl Estradiol, Norethindrone, Ferrous Fumarate interaction page
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 Ethinyl Estradiol, Norethindrone, Ferrous Fumarate 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:
Where Fennel and Ethinyl Estradiol, Norethindrone, Ferrous Fumarate 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.
#88 of 1,452 supplements looked up here in the last 7 days
#229 of 2,830 medications looked up here in the last 7 days
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.
About Fennel
What is 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.
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.
No drugs match “”.
741 interactions
- Diclofenac Sodium ›
- Diltiazem ›
- Nifedipine ›
- Ibuprofen ›
- Aspirin ›
- Hydrocortisone ›
- Naproxen ›
- Erythromycin ›
- Estradiol ›
- Minocycline ›
- Lidocaine ›
- Norethindrone ›
- Testosterone ›
- Verapamil ›
- Levonorgestrel ›
- Prednisone ›
- Quinidine ›
- Cyclosporine ›
- Dexamethasone ›
- Triazolam ›
- Zopiclone ›
- Ciprofloxacin ›
- Colchicine ›
- Fentanyl ›
- Oxybutynin ›
- Prednisolone ›
- Tacrolimus ›
- Temazepam ›
- Budesonide ›
- Carbamazepine ›
- Clindamycin ›
- Dextromethorphan ›
- Diclofenac Potassium ›
- Dipyridamole ›
- Doxorubicin ›
- Fluticasone ›
- Miconazole ›
- Buprenorphine ›
- Conjugated Estrogens ›
- Diazepam ›
- Everolimus ›
- Ivabradine ›
- Ketoprofen ›
- Medroxyprogesterone ›
- Medroxyprogesterone Acetate ›
- Rifampin ›
- Testosterone Undecanoate ›
- Aripiprazole ›
- Bivalirudin ›
- Caffeine (otc Drug) ›
- Ciclesonide ›
- Clonazepam ›
- Cyclobenzaprine ›
- Dapsone ›
- Erythromycin Ethylsuccinate ›
- Erythromycin Stearate ›
- Etoposide ›
- Fluticasone Propionate ›
- Hydroxyzine ›
- Itraconazole ›
Showing 60 of 741 moderate interactions — see all 741 on the Fennel page.
No interaction 2,088 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.
- Levothyroxine ›
- Methylphenidate ›
- Ivermectin ›
- Acetaminophen ›
- Rosuvastatin ›
- Metoprolol ›
- Isotretinoin ›
- Tirzepatide ›
- Levothyroxine, Liothyronine ›
- Docusate ›
- Methamphetamine ›
- Metformin ›
- Lisdexamfetamine ›
- Semaglutide ›
- Hydroxyurea ›
- Valacyclovir ›
- Amphetamine ›
- Propranolol ›
- Sumatriptan ›
- Methotrexate ›
- Lisinopril ›
- Amoxicillin ›
- Fluoxetine ›
- Bupropion ›
- Azithromycin ›
- Doxycycline ›
- Pregabalin ›
- Gabapentin ›
- Dextroamphetamine ›
- Lamotrigine ›
- Bendamustine ›
- Acyclovir ›
- Duloxetine ›
- Methylene Blue ›
- Acetaminophen, Codeine ›
- Candesartan Cilexetil ›
- Amoxicillin, Clavulanate Potassium ›
- Insulin Degludec, Liraglutide ›
- Bisoprolol ›
- Calcium Oxybate, Magnesium Oxybate, Potassium Oxybate, Sodium Oxybate ›
- Amphetamine Aspartate, Amphetamine Sulfate, Dextroamphetamine Saccharate, Dextroamphetamine Sulfate ›
- Aminophylline, Amobarbital, Ephedrine ›
- Acetaminophen, Dichloralphenazone, Isometheptene ›
- Atenolol, Chlorthalidone ›
- Enalapril Maleate ›
- Bendroflumethiazide, Rauwolfia Serpentina ›
- Ephedrine, Phenobarbital, Theophylline ›
- Acetaminophen, Oxycodone ›
- Acetaminophen, Brompheniramine, Phenylpropanolamine ›
- Bismuth Subcarbonate, Calcium Carbonate, Opium ›
- Sulfamethoxazole, Trimethoprim ›
- Ezetimibe ›
- Cephalexin ›
- Rosiglitazone Maleate ›
- Sacubitril, Valsartan ›
- Isoniazid, Pyrazinamide, Rifampin ›
- Levetiracetam ›
- Levodopa ›
- Nebivolol Hydrochloride, Valsartan ›
- Cyclopentolate ›
Showing the 60 most looked-up of 2,088 medications checked with no known interaction — see the full Fennel list.
Sources & How We Checked
Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.
- Natural Medicines (Therapeutic Research Center) — Evidence-graded clinical reference for vitamins, herbs and supplements — the basis for our interaction data.
- MedlinePlus, U.S. National Library of Medicine — NIH consumer drug information, used for the medication overviews.
- NIH Dietary Supplement Label Database (DSLD) — Official supplement product labels.
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
Ethinyl Estradiol, Norethindrone, Ferrous Fumarate Is Linked to Lower Levels of 7 Nutrients
Natural Medicines records Ethinyl Estradiol, Norethindrone, Ferrous Fumarate as a medicine that can lower these. This is not an interaction with Fennel — it is a separate effect of the medicine, and it is a reason some people are advised to supplement rather than to avoid one:
Read the full Ethinyl Estradiol, Norethindrone, Ferrous Fumarate nutrient depletion report ›
Depletion records come from the licensed Natural Medicines database. Do not start a supplement on the strength of this page — ask your pharmacist or doctor whether it applies to you.
Taking Fennel and Ethinyl Estradiol, Norethindrone, Ferrous Fumarate Together: Common Questions
Can you take Fennel with Ethinyl Estradiol, Norethindrone, Ferrous Fumarate?
Why are there 3 interactions listed for Fennel and Ethinyl Estradiol, Norethindrone, Ferrous Fumarate?
How serious is the Fennel and Ethinyl Estradiol, Norethindrone, Ferrous Fumarate interaction?
Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy
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