Drug & supplement interaction

Fennel + Glipizide

Glipizide brand names: Glucotrol, Glucotrol XL.

No Known Interaction
Medically reviewed by · Updated July 2026 · Pair last verified Sep 20, 2026
The bottom line No known interaction

We found no known interaction between Fennel and Glipizide in our sources. Absence of a documented interaction is not the same as proven safety, and does not guarantee one does not exist. Do not start, stop, or change a medication or supplement based on this page; confirm with your pharmacist or doctor first.

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Interaction report

Fennel and Glipizide

We checked these two against our interaction database. Here is what we found.

No Known Interaction Found

We did not find a documented interaction between Glipizide and Fennel in our sources. This does not guarantee that the combination is completely free of risk — there is often limited research on supplements and herbal products, especially around drug interactions.

If you decide to take both, the practical routine is simple: add one new thing at a time and note the date you started it. If the combination is going to disagree with you, it usually shows in the first days to a couple of weeks — and a start date turns “I’ve been feeling off” into something a pharmacist can actually work with. Do not stop a prescribed medicine on your own.

Always talk with your pharmacist or doctor before making changes to your medications or supplements, particularly if you take several medications or have an ongoing health condition.

Fennel safety at a glance

Fennel overall Use caution Generally safe as a food, but concentrated supplements and essential oil need more caution.
Pregnancy Possibly Unsafe When used orally. Observational research has found that regular use of fennel during pregnancy is associated with shortened gestation. Read the full pregnancy detail
Breastfeeding Possibly Unsafe When used orally. Case reports have linked consumption of an herbal tea containing extracts of fennel, licorice, anise, and goat's rue to neurotoxicity in two b... Read the full breastfeeding detail

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center) — the full detail is in the Special populations card below. Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Still wondering about combining Glipizide and Fennel? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
How we checked

Why No Interaction Is Listed for Glipizide

Interactions in our licensed database are recorded against drug classes, not just single drug names. Glipizide is filed under 6 classifications — including sulfonylureas, antidiabetes drugs, cytochrome p450 2c9 (cyp2c9) substrates. Fennel has documented interactions with 6 drug classes — the most serious being anticoagulant/antiplatelet drugs (moderate), ciprofloxacin (cipro) (moderate) and contraceptive drugs (moderate) — and none of Glipizide’s classifications are among them.

Classification data comes from our licensed Natural Medicines dataset. A medication can belong to classes beyond those recorded there, so this describes how the check was run — it is not a safety guarantee.

Keep it in perspective

Fennel Does Interact With Other Medications

Fennel has 740 moderate known drug interactions in our database — Glipizide isn’t one of them. If you take anything else, check it against the full list below.

Moderate 740 No known interaction 2,090 (incl. Glipizide)
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.

What to actually watch for

What Fennel Itself Has Been Linked To

This is not an interaction — nothing below involves Glipizide. It is the side-effect record for Fennel on its own, from the licensed Natural Medicines monograph. If something new turns up after you add Fennel, this list is the first place to look. 4 entries are worth acting on rather than waiting out — marked below.

  • Wheezing Worth acting on Additional detail

    “A case report describes an 11-year-old male who developed an allergy to fennel-containing toothpaste. Immediately after using the toothpaste, the patient experienced sneezing, coughing, itchy mouth, rhinorrhea, nasal congestion, wheezing, difficulty breathing, and palpitations, which resolved within 10 minutes of spitting out the toothpaste and rinsing the mouth.”

    Fennel · Natural Medicines adverse-effect record, reported in allergic rhinitis (hay fever).

    1 source cited
    1. 103822. Denaxa D, Arkwright PD. Fennel as a cause of immediate hypersensitivity to toothpaste. Ann Allergy Asthma Immunol. 2020;125(1):99-100. PubMed

    “Orally, fennel and fennel seed have been reported to cause bronchial asthma.”

    Fennel · Natural Medicines adverse-effect record, reported in asthma.

    1 source cited
    1. 49478. LEVY, S. B. Bronchial asthma due to ingestion of fennel and fennel seed. Ann.Allergy 1948;6(4):415.
  • Seizures Worth acting on Additional detail

    “Orally, fennel oil has been associated with tonic clonic and generalized seizures. New-onset cluster headaches are reported in a 24-year-old female while using a toothpaste containing fennel and camphor for 3 months. The headaches resolved upon stopping the toothpaste. It is unclear if this adverse effect can be attributed to fennel, camphor, or the combination.”

    Fennel · Natural Medicines adverse-effect record, reported in epilepsy.

    2 sources cited
    1. 12868. Burkhard PR, Burkhardt K, Haenggeli CA, Landis T. Plant-induced seizures: reappearance of an old problem. J Neurol 1999;246:667-70. PubMed
    2. 112368. 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
  • Shortness of breath Worth acting on Additional detail

    Recorded for Fennel in the same Natural Medicines adverse-effect record shown under Wheezing above.

  • An allergic reaction Worth acting on Additional detail

    “Advise patients to avoid excessive sunlight or ultraviolet light exposure while using fennel (19). Allergic reactions affecting the skin such as atopic dermatitis and photosensitivity may occur in patients who consume fennel.”

    Fennel · Natural Medicines adverse-effect record, reported in dermatitis.

    3 sources cited
    1. 19. Brinker F. Herb Contraindications and Drug Interactions. 2nd ed. Sandy, OR: Eclectic Medical Publications, 1998.
    2. 6178. Gral N, Beani JC, Bonnot D, et al. [Plasma levels of psoralens after celery ingestion]. Ann Dermatol Venereol 1993;120:599-603.
    3. 49507. 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.
  • Sun sensitivity Additional detail

    Recorded for Fennel in the same Natural Medicines adverse-effect record shown under Seizures above.

  • A stuffy or runny nose / A fast or pounding heartbeat / Cough Additional detail

    Recorded for Fennel in the same Natural Medicines adverse-effect record shown under Wheezing above.

  • Stomach upset Additional detail

    Recorded for Fennel in the same Natural Medicines adverse-effect record shown under Seizures above.

  • A skin rash Additional detail

    Recorded for Fennel in the same Natural Medicines adverse-effect record shown under An allergic reaction above.

Showing the 10 most notable of 13 recorded effects — ranked by how unusual each one is across medicines generally, with serious effects weighted up.

Everything above comes from the Natural Medicines adverse-effect record for Fennel — expand a row for the licensed statement it rests on. We read the ADVERSE REACTIONS section of Glipizide’s FDA label too, and the two lists don’t meaningfully overlap — which is why no Glipizide column appears here.

Special populations

Fennel in Pregnancy & Breastfeeding

Pregnancy Possibly Unsafe

When used orally. Observational research has found that regular use of fennel during pregnancy is associated with shortened gestation.

Lactation Possibly Unsafe

When used orally. Case reports have linked consumption of an herbal tea containing extracts of fennel, licorice, anise, and goat's rue to neurotoxicity in two breast-feeding infants. The adverse effect was attributed to anethole, a constituent of fennel and anise. However, levels of anethole were not measured in breastmilk, and the herbal tea was not tested for contaminants. Furthermore, other adverse effects related to use of fennel during lactation have not been reported. However, until more is known, avoid using.

DISCLAIMER: This tool is intended for informational purposes only, and should not be interpreted as specific medical advice. Patients should consult with a qualified healthcare provider before making decisions about therapies and/or health conditions.© 2026 Therapeutic Research Center

Overlapping uses

What Glipizide Is Prescribed For, and What Fennel Has Been Studied For

These two come up together because they touch the same health topic — not because they do the same job. Glipizide is a prescription medicine with approved uses on its FDA label. Fennel is a supplement: what follows is what researchers have looked at it for, and how strong that evidence is.

Glipizide is prescribed for: Glipizide tablets and glipizide extended-release tablets are both used as an add-on to diet and exercise to improve blood sugar (glucose) control in adults with type 2 diabetes. It is not used for type 1 diabetes or diabetic ketoacidosis (a serious complication of uncontrolled blood sugar).

Fennel has been studied for:

  • Diabetes studied, not established Fennel has been studied for this. Natural Medicines rates the evidence: Insufficient Reliable Evidence To Rate Read what the research shows

    Fennel for diabetes

    Although there has been interest in using oral fennel for diabetes, there is insufficient reliable information about the clinical effects of fennel for this purpose.

Effectiveness ratings and the research summaries above are the verbatim record from the Natural Medicines database, which grades evidence from “Effective” down to “Insufficient Reliable Evidence To Rate”. A rating below the top of that scale means researchers have looked at it — not that it works, and never that it can stand in for a prescribed medicine. Do not stop or replace Glipizide on your own; if you are taking Fennel for the same health topic, tell your prescriber, especially if the medicine is being adjusted to a target.

From our Q&A

Questions About Fennel or Glipizide

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 Glipizide, 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 Glipizide

This page covers Fennel only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Glipizide page lists 307 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Siberian Cocklebur (major), Acai (moderate), Adrafinil (moderate) and African Wild Potato (moderate).

By severity: 2 major · 256 moderate · 49 minor.

From our pharmacist’s overview on the Glipizide page

“Glipizide (Glucotrol, Glucotrol XL) lowers blood sugar by prompting the pancreas to release more insulin, and that same power is why I read its supplement list with real seriousness. Of the 307 ingredients on file, 239 also act on blood glucose, so stacking them can drive sugar dangerously low.”

Reviewed by 2 · Jul 18, 2026

Open the Glipizide 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. Even though Fennel itself has no known interaction with Glipizide, another ingredient on your label might. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Fennel and Glipizide 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%

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

29 days ago today
Medication Glipizide
Top 25%

#507 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.

Where does our data come from?
  • Source: the Natural Medicines (TRC Healthcare) clinical database — the evidence-graded professional reference for herb & supplement interactions.
  • Citation library: 103,510 references behind our interaction content, 65,311 of them resolved to verified PubMed/DOI sources. See every Fennel reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 20, 2026. The Fennel and Glipizide records this page draws on were last updated July 11, 2026.
  • What “no known interaction” means: no documented interaction in the sources above — not a guarantee of safety. Supplements are studied far less than prescription drugs, so we say exactly what the evidence supports, and nothing more.
Data structure & sourcing designed and verified by .
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.

Foeniculum vulgare · Apiaceae · Seeds (fruit), bulb, leaves, and essential oil · Tea, capsules, seeds, essential oil, extracts, and as a food/spice

An interaction check asks whether these two react with each other — it does not ask whether Fennel is a good idea for someone in your situation. Here is what our Fennel record says about it on its own.

Fennel: dosing

There is no single official or standardized dose for fennel as a supplement. The right amount depends on the form (tea, seeds, capsule, or oil) and the product.The best approach is to follow the directions on the product label and not exceed them.

From our Fennel monograph — the full record covers uses, side effects and every documented interaction.

Read the full Fennel monograph & all interactions
Medication

About Glipizide

What Is Glipizide Used For?

Brand names: Glucotrol, Glucotrol XL

Glipizide tablets and glipizide extended-release tablets are both used as an add-on to diet and exercise to improve blood sugar (glucose) control in adults with type 2 diabetes. It is not used for type 1 diabetes or diabetic ketoacidosis (a serious complication of uncontrolled blood sugar).

Most-Reported Side Effects for Glipizide

From FAERS, the FDA’s public side-effect reporting system (0 reports, all brands). Reports are voluntary and are not proof the drug caused the effect.

Blood glucose increased 6,712 reports
Nausea 4,542 reports
Diarrhea 3,383 reports
Fatigue 3,045 reports
Weight decreased 2,832 reports
See full Glipizide drug information
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
740Moderate
0Minor
2,089No known interaction
740 Moderate 2,089 No interaction
Moderate

740 interactions

Showing 60 of 740 moderate interactions — see all 740 on the Fennel page.

No interaction 2,089 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 2,089 medications checked with no known interaction — see the full Fennel list.

See the full Fennel interactions page
See every supplement checked against Glipizide, ranked by severity
Evidence & sources

Fennel References

The 17 references that drive our Fennel monograph and interaction data, from the evidence-graded Natural Medicines (TRC Healthcare) database. Citations with a link open the study on PubMed or the publisher’s site.

  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

Medication overviews come from MedlinePlus (NIH); supplement label data from the NIH Dietary Supplement Label Database. Content is written and reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

Pharmacist Counseling Corner

Taking Fennel and Glipizide Together: Common Questions

Is it safe to take Fennel with Glipizide?
We do not list a known interaction between Fennel and Glipizide. That does not guarantee the combination is risk-free, so confirm with your pharmacist or doctor — especially if you take other medications or have a health condition.
Are Fennel and Glipizide used for the same thing?
They overlap in purpose, which usually means the real question is whether you need both rather than whether they are safe together. This page lists the shared uses and how strong the evidence is for Fennel in each. That is a conversation for your prescriber, especially if Glipizide is being adjusted to a target.
How was the Fennel and Glipizide combination checked?
Interactions in our licensed database are recorded against drug classes. Glipizide is filed under 6 classifications, and Fennel has documented interactions with 6 drug classes — none of Glipizide's classifications are among them. A medication can belong to classes beyond those recorded in our dataset, so this describes how the check was run rather than guaranteeing safety.
Does Fennel interact with any other medications?
Yes. Fennel has 740 documented drug interactions in our database — Glipizide is simply not one of them. If you take anything else, it is worth checking each one; they are all listed on this page.
Does Glipizide interact with any supplements?
Yes. Glipizide has documented interactions with 307 supplements in our database — Fennel is not one of them. The Glipizide interaction page linked on this page lists every one, ranked by severity.

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

Where next

Keep Exploring

Fennel monograph Uses, safety profile, and every drug interaction in one place Glipizide drug information The full plain-English guide to this medication Glipizide supplement interactions Every supplement checked against Glipizide, 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 References The 17 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Glipizide 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.