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Dietary supplement

Fennel Seed 450 mg Ingredients & Drug Interactions

by Dr. Clark Research Association Dr. Clark Zentrum

Fennel Seed 450 mg label
See full label image
Capsule Category: Botanical
Most serious interaction: Moderate
Clinical methodology reviewed by · Updated Sep 30, 2026 · Label data from the NIH DSLD
What is this page for?

First and foremost: checking Fennel Seed 450 mg 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 Seed 450 mg is a dietary supplement by Dr. Clark Research Association Dr. Clark Zentrum 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. 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 Seed 450 mg by Dr. Clark Research Association Dr. Clark Zentrum

Ask about any prescription or over-the-counter medication and we check it for interactions with Fennel Seed 450 mg by Dr. Clark Research Association Dr. Clark Zentrum — and tell you which ingredient is responsible.

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HelloPharmacist Scorecard of Fennel Seed 450 mg by Dr. Clark Research Association Dr. Clark Zentrum

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 30, 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 supplement contains one active ingredient: fennel seed at 450 mg per capsule. Fennel is a plant seed used in traditional medicine and cooking, with constituents that have estrogen-like activity in the body.

The capsule itself is made from gelatin.

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).

Fennel seed has possibly effective evidence for dysmenorrhea (painful periods). For other uses listed in our data — bronchitis, anxiety, nocturnal enuresis (bedwetting), and cholera — the evidence is insufficient to establish whether it works.

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 seed is generally well tolerated when used as a food. As a concentrated medicinal supplement, caution is warranted.

The most common side effects reported are gastrointestinal discomfort, photosensitivity, and allergic reactions in sensitive individuals. A rare serious side effect — seizures — has been reported.

Some people have experienced bronchial asthma symptoms from fennel, and allergic reactions ranging from sneezing and itchy mouth to wheezing and difficulty breathing have occurred in sensitive individuals. During pregnancy, fennel in medicinal or concentrated amounts is rated possibly unsafe due to limited safety data and its hormone-like effects.

During breastfeeding, food amounts are likely fine, but medicinal doses and fennel essential oil are not well studied — talk with your doctor or pharmacist about what's appropriate for you.

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 fennel seed, double-check with your pharmacist or doctor if you take blood thinners or antiplatelet drugs (the most serious risk is increased bleeding), birth control pills, hormone replacement therapy, tamoxifen, ciprofloxacin, or any medications processed by your liver's CYP3A4 pathway. No interactions are documented for any ingredients we could not check, but the ones above warrant a conversation.

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 may be worth considering if you have painful periods and want a supplement with some research behind it. However, if you take birth control, hormone replacement therapy, blood thinners, ciprofloxacin, tamoxifen, or drugs metabolized by your liver's CYP3A4 system, you'll want to discuss this supplement with your doctor or pharmacist first — the interactions are real enough to matter.

Pregnant or breastfeeding? Check with your healthcare provider before using medicinal amounts.

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 Sep 24, 2021.

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 Seed 450 mg, straight from the product label.

Brand Dr. Clark Research Association Dr. Clark Zentrum
Barcode (UPC) 7640116925021
Net contents 450 mg; 120 Capsule(s)
Market status On market
Date entered into DSLD Sep 24, 2021
DSLD ID 255099
Product type Botanical
Supplement form Capsule
Dietary claims / uses All Other
Intended target group(s) Children 4 or More Years of Age, Adult (18 - 50 Years)
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 Seed 450 mg by Dr. Clark Research Association Dr. Clark Zentrum, 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:
1 Capsule(s)
Maximum serving Sizes:
3 Capsule(s)
Servings per container
40
UPC/BARCODE
7640116925021
IngredientAmount% DV
Fennel1350 mg--

Other ingredients: Fennel, Gelatin

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.
FDA Statement of Identity

Dietary Supplement/Food Supplement

Suggested/Recommended/Usage/Directions

Adults and children 12 or more years of age: Up to 3 capsules 3 times a day or as directed.

Best before: see expiration date.

Storage

Store out of reach of young children. Store in a dry, cool place.

Precautions

Dietary supplements/food supplements should not be used as a substitute for a varied diet. Do not exceed the stated recommended daily dose.

Formulation

Made in the USA.

General Statements

Nominal weight: 66 g

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

See for yourself

Fennel Seed 450 mg by Dr. Clark Research Association Dr. Clark Zentrum label

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

Fennel Seed 450 mg 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 Seed 450 mg by Dr. Clark Research Association Dr. Clark Zentrum

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

Serving size1 Capsule(s) Dosage formCapsule Servings per container40 Amounts shown are per serving.

Fennel

Interacts with
740 drugs
1350 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 monograph & interactions

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

Interaction report

Fennel Seed 450 mg by Dr. Clark Research Association Dr. Clark Zentrum Drug Interactions

Want to check YOUR meds against Fennel Seed 450 mg?

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 740

Individual Drug Interactions

The ingredients in Fennel Seed 450 mg interact with 740 drugs. Click any drug to see the details.

1 of the 1 ingredient in Fennel Seed 450 mg interact with drugs. Each result below shows which ingredient is responsible. Fennel

Each ingredient & the kinds of drugs it affects

For each ingredient in Fennel Seed 450 mg 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.

Fennel6 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 full monograph & interactions
The maker

Brand information

Manufacturer and brand details for Fennel Seed 450 mg, from the product label.

Dr. Clark Research Association Dr. Clark Zentrum

See all Dr. Clark Research Association Dr. Clark Zentrum products
Name
Dr. Clark Zentrum Limited
Street Address
152 Naxxar Road #7, SGN 9030
City
San Gwann
State
Malta
Web Address
www.drclark.com
Pharmacist Counseling Corner

Fennel Seed 450 mg by Dr. Clark Research Association Dr. Clark Zentrum: Common Questions

Does Fennel Seed 450 mg by Dr. Clark Research Association Dr. Clark Zentrum interact with any medications?
Yes. Based on its ingredients, Fennel Seed 450 mg 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 Seed 450 mg 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.
What is fennel seed actually used for?
Fennel seed has possibly effective evidence for dysmenorrhea — that's painful periods. For other conditions like bronchitis, anxiety, bedwetting, and cholera, we don't have enough reliable evidence to say whether it works.
Can I take this while pregnant?
No — medicinal or concentrated amounts of fennel are rated possibly unsafe in pregnancy due to limited safety data and its hormone-like effects on the body. Talk with your doctor about what's safe for you.
Is it safe while breastfeeding?
Food amounts of fennel are likely okay, but medicinal doses and fennel essential oil haven't been well studied during breastfeeding. Discuss with your pharmacist or doctor whether this supplement is right for you.
What side effects might I experience?
Most commonly, gastrointestinal discomfort, photosensitivity, and allergic reactions in sensitive people. Rare but serious, seizures have been reported. Some people have also experienced bronchial asthma symptoms or allergic reactions ranging from sneezing to difficulty breathing.
Can fennel affect how my birth control works?
Yes — fennel's estrogen-like activity may interfere with contraceptive effectiveness, especially in large amounts. If you take birth control, confirm with your pharmacist or doctor that this supplement is safe to combine with yours.
What's in the capsule besides fennel?
The capsule is made from gelatin, which is an inactive ingredient that holds the fennel seed powder inside.

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

Not sure if Fennel Seed 450 mg is safe with your meds?

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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 Seed 450 mg label
Go deeper

The Full Monographs Behind Fennel Seed 450 mg’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 Seed 450 mg'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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