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Dietary supplement

Fennel Ingredients & Drug Interactions

by Alvita

Fennel label
See full label image
Other (e.g. Tea Bag) 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 Alvita 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 by Alvita

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

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HelloPharmacist Scorecard of Fennel by Alvita

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.

Alvita Fennel is a single-ingredient tea with fennel as its active component. The product contains no other active ingredients, and there are no inactive fillers listed.

Does it work?

Not established
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
Not established

The graded evidence we hold for these ingredients covers different conditions than the ones this product is marketed for, so there's no established rating for its stated use — see Fennel's own graded uses on its monograph.

Why this rating?
  • The label markets this product for: Alleviate bloating and gas.
  • We looked for evidence on: Flatulence, Dyspepsia, Irritable bowel syndrome (IBS), Abdominal distension, Digestive discomfort, Intestinal gas — and 1 related terms.
  • The closest evidence on file: Fennel is rated "Insufficient Reliable Evidence To Rate" for Dyspepsia (Natural Medicines).
  • Also on file: Fennel is rated "Insufficient Reliable Evidence To Rate" for Flatulence, Irritable bowel syndrome (IBS).

Fennel is rated possibly effective for dysmenorrhea (menstrual pain). For bronchitis, anxiety, nocturnal enuresis (bedwetting), and cholera, the evidence isn't established in the data we hold—the research is either too limited or unreliable to say 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 is generally well tolerated when used as a food or mild tea. The most common side effects are gastrointestinal discomfort, sensitivity to sunlight (photosensitivity), and allergic reactions in sensitive people.

Seizures are rare but have been reported. Avoid medicinal or concentrated amounts during pregnancy due to limited safety data and hormone-like effects.

Food amounts are likely fine while breastfeeding, but medicinal doses and fennel essential oil aren't well studied in that context—talk with your pharmacist or doctor if you're nursing.

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 Alvita Fennel, double-check with your pharmacist if you use blood thinners (anticoagulants or antiplatelet drugs), birth control pills, hormone replacement therapy, drugs metabolized by CYP3A4, ciprofloxacin, or tamoxifen. These moderate interactions could reduce drug effectiveness or increase bleeding risk.

Check your own medication Run your meds through the checker above

The bottom line

Scorecard at a glanceFully disclosed formula with no established evidence rating for its marketed use. Moderate medication interactions have been identified, and safety information is well characterized.

Fennel tea may help with menstrual cramps, but it interacts with blood thinners, birth control, hormone replacement therapy, and several other drugs. If you take any prescription medications—especially for blood clotting, contraception, cancer, or infections—check with your pharmacist before adding this product.

Pregnant women should avoid 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 Jul 21, 2022.

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 Alvita
Net contents 24 Tea Bag(s); 1.98 Oz(s); 56 Gram(s)
Market status On market
Date entered into DSLD Jul 21, 2022
DSLD ID 268566
Product type Botanical
Supplement form Other (e.g. Tea Bag)
Dietary claims / uses All Other, Structure/Function
Intended target group(s) Adult (18 - 50 Years), Kosher, Organic
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 Alvita, 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 Tea Bag(s)
Maximum serving Sizes:
1 Tea Bag(s)
Servings per container
24
IngredientAmount% DV
Fennel2.33 Gram(s)--

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.
Formulation

Organic

Traditionally used to help alleviate bloating and gas*

Naturally caffeine free

Alvita chooses only the highest quality organic, wildcrafted, or cultivated botanicals, perfectly prepared to provide you with the best Mother Nature has to offer. Historical and scientific literature is painstakingly studied to ensure that the correct traditional plant and most appropriate servings are used, delivering premium flavor and quality.

Fennel Fennel (Foeniculum vulgare) was first cultivated by the ancient Romans, who used the fruits of the plant as a culinary ingredient. Fennel was also traditionally used to help alleviate bloating and gas. The plant's use as both a popular culinary ingredient and a digestive aid continued to grow over the centuries.

Certified Organic by QAI.

Brand IP Statement(s)

Alvita Since 1922

FDA Statement of Identity

Herbal Supplement

Seals/Symbols

USDA Organic

Quality Assurance International Certified Organic Star-K (Kosher)

Suggested/Recommended/Usage/Directions

Preparation Place one tea bag in a cup and add 6 oz of boiling water. Cover and steep for 10 minutes. Gently squeeze tea bag and remove. Directions for use: We recommend 3 cups daily. Add sweetener if desired

How to brew Pour 6 oz 1 Temp 212 Degrees F 2 Steep 10 min 3

Formula

Star-K (Kosher)

Alvita Fennel Tea is made with premium-quality, organic fennel seeds, and has a sweet aroma and flavor reminiscent of licorice or anise.

General Statements

The Alvita Story… In 1922, a new era for tea consumption began in America. The herb alfalfa, long known for its beneficial nutrients, was packaged in tea bags and sold to an emerging health food market. This product became known as Alvita and set the standard for future herbal teas. Today, Alvita represents more than forty single-ingredient teas, each one uniquely distinct, just like the individuals who drink them.

Herbs are gifts from the earth. Alvita takes its stewardship seriously by offering carefully harvested teas in earth-friendly packaging. Our beautifully illustrated boxes are made using recycled paperboard and our English, pillow style tea bags are oxygen bleached, not chlorine treated. You won’t find a better product, with a cleaner package… anywhere. Alvita… brewed with confidence, steeped in tradition.

100% Recycled Paperboard Recyclable

Precautions

WARNING: If you are pregnant or nursing, taking any medication or have any medical condition, consult a health care professional before use.

Keep out of reach of children.

FDA Disclaimer Statement

These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.

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

See for yourself

Fennel by Alvita 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 Alvita

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

Serving size1 Tea Bag(s) Dosage formOther (e.g. Tea Bag) Servings per container24 Amounts shown are per serving.

Fennel

Interacts with
740 drugs
2.33 Gram(s) 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
Interaction report

Fennel by Alvita 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 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

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.

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, from the product label.

Alvita

See all Alvita products
Name
TWINLAB CORPORATION
City
AMERICAN FORK
State
UT
ZipCode
84003
Phone Number
1-800-645-5626
Pharmacist Counseling Corner

Fennel by Alvita: Common Questions

Does Fennel by Alvita 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.
Does fennel actually help with period cramps?
Fennel is rated possibly effective for dysmenorrhea (menstrual pain), meaning the evidence supports it may help, but the research isn't airtight. If you want to try it, talk to your pharmacist first, especially if you're on any medications.
What are the most common side effects?
Most people tolerate fennel well. The most common side effects are stomach discomfort, sensitivity to sunlight, and allergic reactions in sensitive individuals. Seizures are rare but have been reported.
Can I use fennel tea while pregnant?
Avoid medicinal or concentrated amounts during pregnancy due to limited safety data and possible hormone-like effects. Talk with your doctor or pharmacist if you're pregnant and considering fennel.
Can I use fennel while breastfeeding?
Food amounts are likely fine while breastfeeding, but medicinal doses and fennel essential oil aren't well studied in that context. If you're nursing and want to use fennel as a supplement, check with your pharmacist or doctor first.
Why does fennel interact with birth control?
Fennel contains compounds with estrogenic (hormone-like) activity. In theory, taking large amounts might compete with how your birth control works and reduce its effectiveness—though this hasn't been proven in humans.

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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