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Dietary supplement

Fennel Ingredients & Drug Interactions

by Hawaii Pharm

Fennel label
See full label image
Liquid Category: Botanical
Most serious interaction: Moderate
Clinical methodology reviewed by · Updated Sep 16, 2026 · Label data from the NIH DSLD
What is this page for?

First and foremost: checking Fennel against your medications. The heart of this page is the interaction checker and the full interaction report — how this product’s ingredients may interact with prescription and over-the-counter medicines you may be taking.

Around that, we add a pharmacist’s high-level view of the product as a whole — what’s inside, the evidence for its stated use, how transparent the label is, and what safety data exists — so you can see the full picture in one place. It’s educational information from our licensed clinical databases and the clinical staff at HelloPharmacist — not medical advice — and we don’t sell or endorse products. Our editorial policy

The interaction bottom line Most serious interaction: Moderate

Fennel is a dietary supplement by Hawaii Pharm with 1 active ingredient. Its ingredients are commonly taken for digestive upset and bloating, infant colic, menstrual cramps.Based on those ingredients, 740 medications have a known interaction with it, the most serious rated moderate. The ingredients most likely to interact are Fennel Seed Extract, Dry. Use the checker below to test your specific medication, or read the full HelloPharmacist Interaction Report.

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Check Your Meds Against Fennel by Hawaii Pharm

Ask about any prescription or over-the-counter medication and we check it for interactions with Fennel by Hawaii Pharm — and tell you which ingredient is responsible.

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HelloPharmacist Scorecard of Fennel by Hawaii Pharm

Our pharmacy team’s full take, with four database checks built into the cards below — a summary of what is known, not a grade of the product itself.

From our pharmacy team — supplement deep dive

Generated from HelloPharmacist’s pharmacist-curated databases and editorial rules · Last generated Jul 11, 2026

What’s inside

Full disclosure
Ingredient Transparency · database check
Full

Every active ingredient lists its own amount on the label.

Why this rating?
  • The label discloses an exact amount for 1 of its 1 active ingredient.
  • No proprietary blends here — you can verify the dose of every single component.

This product contains one active ingredient: fennel seed extract in concentrated, dried form. Fennel has been used traditionally to support digestive comfort and other health purposes.

The liquid also includes alcohol, water, and glycerin as inactive ingredients that help deliver and preserve the extract.

Does it work?

Moderate evidence
Evidence for Intended Use · database check
By FDA rules, dietary supplements can’t claim to treat, cure, or prevent disease — so labels speak in careful marketing language. We discern each product’s intended use from its name, label claims, and label statements, then grade the clinical evidence for that use. How these ratings are computed

This product doesn't appear to be marketed for a specific use, so we graded Fennel's overall clinical evidence instead.

Moderate

Some clinical evidence supports Fennel for:

Why this rating?
  • We looked at the product name, claims, and label statements and couldn't find a stated purpose to grade.
  • Since the label doesn't commit to one use, we graded the ingredient's overall clinical evidence instead.
  • On file: Dysmenorrhea — rated "Possibly Effective" (Natural Medicines).

The evidence supports fennel for dysmenorrhea (period pain)—it's rated possibly effective for that use. For other traditional uses like bronchitis, anxiety, bedwetting, and cholera, there isn't enough reliable evidence in our data to establish whether fennel works.

If you're considering it for one of those conditions, talk with your pharmacist or doctor about what the current research shows.

The evidence, ingredient by ingredient Fennel

How safe is it?

Well-documented data
Safety Information · database check
Well characterized

Adverse-effect, pregnancy, and general safety data are on file for most of these ingredients.

Why this rating?
  • We hold adverse-effect (side-effect) data for 1 of the 1 matched ingredient.
  • Pregnancy & breastfeeding safety ratings cover 1 of 1.
  • General safety write-ups exist for 1 of 1.
  • Remember: this measures how much safety information exists. Thin data is not the same as being safe.

Fennel is generally well tolerated when used as a food, but concentrated supplements like this one warrant more caution. The most common side effects from oral use are gastrointestinal discomfort, sun sensitivity, and allergic reactions in sensitive people.

A rare serious effect (seizures) has been reported. Some people have had allergic reactions—including wheezing, difficulty breathing, and nasal congestion—after contact with fennel products.

During pregnancy, avoid medicinal or concentrated amounts of fennel because safety data is limited and it has hormone-like effects. While breastfeeding, food amounts are likely fine, but medicinal doses and fennel essential oil haven't been well studied—talk with your doctor or pharmacist for personalized guidance.

If you have asthma or a known fennel allergy, use caution.

Side effects, ingredient by ingredient Fennel

Meds to double-check

Moderate interaction found
Known Interaction Concern · database check
Moderate identified

The most serious documented interaction for these ingredients is Moderate. Check your medications for a personalized result.

Why this rating?
  • 1 of the 1 matched ingredient can interact with medications — Fennel.
  • The most serious interaction on file is rated Moderate.
  • Some involve high-stakes drug classes: anticoagulant / antiplatelet drugs.
  • For scale: 741 individual medications appear in the full list. A big number alone doesn't make a product dangerous — what matters is whether YOUR medication is on it, so run yours through the interaction checker on this page.

Before taking this fennel extract, double-check if you use blood thinners or antiplatelet drugs (like warfarin or clopidogrel), birth control pills, hormone replacement therapy, tamoxifen, ciprofloxacin, or any medications broken down by your liver's CYP3A4 enzyme. All of these have documented moderate-severity interactions with fennel.

Check your own medication Run your meds through the checker above

The bottom line

Scorecard at a glanceFully disclosed formula with some supporting evidence behind its ingredients' uses. Moderate medication interactions have been identified, and safety information is well characterized.

Fennel seed extract may help with period pain, but it interacts with blood thinners, birth control, hormone therapy, tamoxifen, and some antibiotics and other medications. If you take any prescription drugs—especially those—check them against this product before you start.

A quick conversation with your pharmacist can keep you safe.

Educational only — not medical advice; always confirm with your pharmacist. Our editorial policy · How we use AI

Assessment coverage: 1 of 1 active ingredient matched to our full ingredient reviews (monographs). Based on the product label dated Oct 24, 2023.

This Scorecard evaluates available label information, ingredient evidence, and known medication-safety considerations. It does not independently verify product identity, purity, potency, contamination, or manufacturing quality. How these ratings are computed

At a glance

General information

Key facts about Fennel, straight from the product label.

Brand Hawaii Pharm
Barcode (UPC) 840253621610
Net contents 4 Fluid Ounce(s); 120 mL
Market status On market
Date entered into DSLD Oct 24, 2023
DSLD ID 301582
Product type Botanical
Supplement form Liquid
Dietary claims / uses All Other, Structure/Function
Intended target group(s) Adult (18 - 50 Years), Gluten Free
From the label
Everything in this section is reproduced from the manufacturer’s own product label — it’s the label speaking, not HelloPharmacist. We show it so you can see exactly what the maker states; we don’t verify or endorse those statements.

Supplement Facts

The label details for Fennel by Hawaii Pharm, sourced from the NIH Dietary Supplement Label Database.

Supplement Facts

Daily Value (DV) Target Group(s):
Adults and children 4 or more years of age
Minimum serving Sizes:
0.7 mL
Maximum serving Sizes:
1 mL
Servings per container
120
UPC/BARCODE
840253621610
IngredientAmount% DV
Fennel Seed Extract, Dry983 mg--

Other ingredients: Alcohol, Water, Glycerin

Tap any ingredient to jump to its full detail below.

Label statements
These statements are the manufacturer’s wording, reproduced from the product label — the label is saying it, not HelloPharmacist. We don’t verify or endorse them.
Brand IP Statement(s)

Hawaii Pharm Herbal Extract Highest quality since 2008

Suggested/Recommended/Usage/Directions

Suggested use: Shake well before using. For adults add about 20-30 drops (0.7-1 mL, one full squeeze of the dropper bulb) to some juice or water, up to 4 times a day.

Precautions

Warning: We recommend to seek expert medical advice before taking.

Do not use if you are allergic to any ingredients.

Consult your physician before giving to children under 18, during pregnancy, if nursing or taking medications.

Consult your physician before giving to children under 18, during pregnancy, if nursing or taking medications.

May affect the ability to drive and operate machinery. May have contraindications, can cause side effects and adverse reactions. Do not use if seal is broken or missing.

Keep out of the reach of children!

Storage

Store in a cool dry place.

Seals/Symbols

cGMP Made in compliance with cGMP 21 CFR 111 in an FDA registered and inspected facility.

Organic Alcohol Based USA Made in United States of America

FDA Disclaimer Statement

This product has not been evaluated by the FDA and is not intended to diagnose, treat, cure or prevent any disease.

General Statements

Scan this QR-code to get 15% discount on your next purchase. Limited time deal.

Formula

Foeniculum vulgare

Organic Alcohol Based

Formulation

Only natural ingredients Purity is laboratory tested and verified

All the raw materials are gluten-free by their nature No artificial colors, flavors, or preservatives

Not tested on animals

Organic Alcohol Based

Made in USA, Hawaii

FDA Statement of Identity

Herbal Supplement

Is this label outdated? Report a formula or label change and our pharmacy team will review it.

See for yourself

Fennel by Hawaii Pharm label

The label scan from the NIH Dietary Supplement Label Database. Tap to enlarge.

Fennel label

Label images are published by the NIH Dietary Supplement Label Database for the version of this product on file. Always read your actual product label.

View the full label (PDF)
What’s inside

The Ingredients in Fennel by Hawaii Pharm

This is the 1 active ingredient this product is made of. Select it to open its full monograph.

Serving size0.7 mL Dosage formLiquid Servings per container120 Amounts shown are per serving.

Fennel Seed Extract, Dry

Interacts with
740 drugs
983 mg per serving

Fennel is a Mediterranean herb widely used as a food and spice, and traditionally taken for digestive complaints, colic, and menstrual cramps. Some sm...

Fennel Seed Extract, Dry monograph & interactions

Other (inactive) ingredients: Alcohol, Water, Glycerin. These complete the product’s ingredient list but are not active constituents.

Interaction report

Fennel by Hawaii Pharm Drug Interactions

Want to check YOUR meds against Fennel?

Ask about interactions with your drugs in plain English — “Can I take it with lisinopril?” — and we find you the answer in seconds, ingredient by ingredient.

 Go to the checker
740Drugs
740 Moderate

Ingredients driving the most interactions

Fennel Seed Extract, Dry 740

Individual Drug Interactions

The ingredients in Fennel interact with 740 drugs. Click any drug to see the details.

1 of the 1 ingredient in Fennel interact with drugs. Each result below shows which ingredient is responsible. Fennel Seed Extract, Dry

Each ingredient & the kinds of drugs it affects

For each ingredient in Fennel with known interactions, here are the types of medications it can affect. Open any type for the detail — or search your exact drug in the checker above.

Fennel Seed Extract, Dry6 drug types · 740 drugs

Anticoagulant/Antiplatelet Drugs

Theoretically, fennel might increase the risk of bleeding when used with antiplatelet or anticoagulant drugs.

Animal research suggests that fennel oil has antithrombotic and antiplatelet effects.

Likelihood Possible Evidence D
Ciprofloxacin (Cipro)

Theoretically, fennel might decrease the levels and clinical effects of ciprofloxacin.

Animal research shows that fennel reduces ciprofloxacin bioavailability by nearly 50%, possibly due to the metal cations such as calcium, iron, and magnesium contained in fennel. This study also found that fennel increased tissue distribution and slowed elimination of ciprofloxacin.

Likelihood Probable Evidence D
Contraceptive Drugs

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.

Likelihood Possible Evidence D
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.

Likelihood Possible Evidence D
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.

Likelihood Possible Evidence D
Tamoxifen (Nolvadex)

Theoretically, taking large amounts of fennel might decrease the antiestrogenic effect of tamoxifen.

Some constituents of fennel have estrogenic activity, which may interfere with the antiestrogenic activity of tamoxifen.

Likelihood Possible Evidence D
Fennel Seed Extract, Dry full monograph & interactions
The maker

Brand information

Manufacturer and brand details for Fennel, from the product label.

Hawaii Pharm

See all Hawaii Pharm products
Name
Hawaii Pharm LLC
Street Address
510 Sumner St. Ste. 613
City
Honolulu
State
HI
ZipCode
96817
Phone Number
888-854-2924
Web Address
www.hawaiipharm.com
Pharmacist Counseling Corner

Fennel by Hawaii Pharm: Common Questions

Does Fennel by Hawaii Pharm interact with any medications?
Yes. Based on its ingredients, Fennel has a known interaction with 740 medications. Use the checker to see how it interacts with a specific drug.
How can one product interact with so many drugs?
Fennel contains a single active ingredient, and that one ingredient can interact with many different medications on its own. We check it against each medication and show the mechanism responsible.
Where does this information come from?
The product label data comes from the NIH Dietary Supplement Label Database (DSLD); the interaction data is built on the Natural Medicines database and reviewed by HelloPharmacist pharmacists.
Will fennel help with period pain?
Fennel is rated possibly effective for dysmenorrhea (period pain), which means there's evidence it may help, though more research would strengthen that conclusion. If you're interested in trying it for that, talk with your pharmacist first—especially if you're on any medications.
What are the most common side effects?
Most people tolerate fennel well, but oral use can cause gastrointestinal discomfort, sun sensitivity (photosensitivity), and allergic reactions in people who are sensitive to it. Rare cases of seizures have been reported. If you have asthma or a fennel allergy, be extra cautious.
Is it safe to take fennel while breastfeeding?
Food amounts of fennel are likely fine while breastfeeding, but medicinal doses and fennel essential oil haven't been well studied in nursing mothers. For personalized guidance on whether this concentrated supplement is right for you, talk with your doctor or pharmacist.
Can I take this if I'm on birth control?
No—there's a documented moderate interaction. Fennel has compounds that mimic estrogen and may weaken how your birth control works. Check with your pharmacist before using this product if you're on any hormone-related medication, including contraceptives, hormone therapy, or tamoxifen.
Why does this product have alcohol in it?
The liquid form includes alcohol, water, and glycerin as inactive ingredients that help preserve and deliver the fennel extract. These are excipients—not active medicine—but they're part of how the product is formulated.

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

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Label information is sourced from the NIH Dietary Supplement Label Database and reflects the product version on file; always read your actual product label. This page is for education only and is not a substitute for professional medical advice. Confirm with your pharmacist or doctor before combining supplements and medications.

Fennel label
Go deeper

The Full Monographs Behind Fennel’s Ingredients

Every ingredient we hold a full HelloPharmacist monograph for — uses, evidence, safety, and the complete interaction list.

Herb & supplement monograph

Fennel

Interacts with 740 drugs

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...

Read the full Fennel monograph →
Sources

Sources & How We Checked

Fennel's label data comes from the NIH Dietary Supplement Label Database; the ingredient interaction data is from the Natural Medicines database, reviewed by our pharmacists.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

The 17 references behind this product’s interaction data

Every citation that drives the interaction findings for this product’s ingredients, from the evidence-graded Natural Medicines (TRC Healthcare) database. Open an ingredient to browse its citations — links open the study on PubMed or the publisher’s site.

Fennel 17 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.
  2. Brinker F. Herb Contraindications and Drug Interactions. 2nd ed. Sandy, OR: Eclectic Medical Publications, 1998.
  3. Zhu M, Wong PY, Li RC. Effect of oral administration of fennel (Foeniculum vulgare) on ciprofloxacin absorption and disposition in the rat. J Pharm Pharmacol 1999;51:1391-6.
  4. Gral N, Beani JC, Bonnot D, et al. [Plasma levels of psoralens after celery ingestion]. Ann Dermatol Venereol 1993;120:599-603.
  5. Burkhard PR, Burkhardt K, Haenggeli CA, Landis T. Plant-induced seizures: reappearance of an old problem. J Neurol 1999;246:667-70. PubMed
  6. Rosti L, Nardini A, Bettinelli ME, Rosti D. Toxic effects of a herbal tea mixture in two newborns. Acta Paediatrica 1994;83:683. PubMed
  7. Cuzzolin L, Zaffani S, and Benoni G. Safety implications regarding use of phytomedicines. Eur.J Clin Pharmacol. 2006;62:37-42. PubMed
  8. Tognolini, M., Ballabeni, V., Bertoni, S., Bruni, R., Impicciatore, M., and Barocelli, E. Protective effect of Foeniculum vulgare essential oil and anethole in an experimental model of thrombosis. Pharmacol.Res 2007;56(3):254-260. PubMed
  9. 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
  10. Tognolini, M., Barocelli, E., Ballabeni, V., Bruni, R., Bianchi, A., Chiavarini, M., and Impicciatore, M. Comparative screening of plant essential oils: phenylpropanoid moiety as basic core for antiplatelet activity. Life Sci. 2-23-2006;78(13):1419-1432. PubMed
  11. 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
  12. LEVY, S. B. Bronchial asthma due to ingestion of fennel and fennel seed. Ann.Allergy 1948;6(4):415.
  13. Ottolenghi, A., De Chiara, A., Arrigoni, S., Terracciano, L., and De Amici, M. [Diagnosis of food allergy caused by fruit and vegetables in children with atopic dermatitis]. Pediatr Med Chir 1995;17(6):525-530.
  14. Trabace L, Tucci P, Ciuffreda L, et al. "Natural" relief of pregnancy-related symptoms and neonatal outcomes: above all do no harm. J Ethnopharmacol. 2015;174:396-402. PubMed
  15. Denaxa D, Arkwright PD. Fennel as a cause of immediate hypersensitivity to toothpaste. Ann Allergy Asthma Immunol. 2020;125(1):99-100. PubMed
  16. Lee HW, Ang L, Lee MS, Alimoradi Z, Kim E. Fennel for reducing pain in primary dysmenorrhea: a systematic review and meta-analysis of randomized controlled trials. Nutrients 2020;12(11):3438. PubMed
  17. Mathew T, John SK, Javali M, Vasireddy M, Nadig R, Sarma GRK. Substance use related cluster headache: A case series. Headache 2022;62(7):908-910. PubMed

See these in context on the Fennel monograph →

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

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