Drug & supplement interaction

Rosemary + Metronidazole

Metronidazole brand names: Flagyl, Protostat, Metronidazole, Nidazol, Trikacide, and others.

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 Rosemary and Metronidazole 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. Additionally, although there is no interaction, the two are separately associated with some of the same side effects, which would make a new symptom harder to attribute to one or the other.

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Interaction report

Rosemary and Metronidazole

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 Metronidazole and Rosemary 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.

Rosemary safety at a glance

Rosemary overall Generally safe Safe in normal culinary amounts; concentrated extracts and undiluted essential oil require caution.
Pregnancy Possibly Unsafe When used orally in medicinal amounts. Rosemary might have uterine and menstrual flow stimulant effects, and might increase metabolism of estradiol and estrone;... Read the full pregnancy detail
Breastfeeding Use caution Food amounts are likely fine, but there is not enough safety data on medicinal doses, so avoid them.

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 Metronidazole and Rosemary? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
How we checked

Why No Interaction Is Listed for Metronidazole

Interactions in our licensed database are recorded against drug classes, not just single drug names. Metronidazole is filed under 8 classifications — including cytochrome p450 2c9 (cyp2c9) inhibitors, qt interval-prolonging drugs, cytochrome p450 3a4 (cyp3a4) inhibitors. Rosemary has documented interactions with 6 drug classes — the most serious being anticoagulant/antiplatelet drugs (moderate), antidiabetes drugs (moderate) and aspirin (moderate) — and none of Metronidazole’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

Rosemary Does Interact With Other Medications

Rosemary has 212 moderate, 160 minor known drug interactions in our database — Metronidazole isn’t one of them. If you take anything else, check it against the full list below.

Moderate 212 Minor 160 No known interaction 2,458 (incl. Metronidazole)
Taking anything else?

Check Another of Your Medications Against Rosemary

Covers the 2,830 medications we’ve checked against Rosemary. Pick one to open its full report.

What to actually watch for

No Interaction Found — But Data Suggests Rosemary and Metronidazole May Share Several of the Same Side Effects

This is not an interaction. Neither one changes how your body handles the other, and nothing here says they react together. What our sources do show is that each has separately been linked to the effects below — so taking both can make those effects more likely to turn up, and harder to pin on one or the other if they do. 2 of them are worth acting on rather than waiting out — marked below.

  • Seizures Worth acting on Additional detail

    Rosemary

    “Orally, the undiluted oil, as well as the camphor constituent of rosemary, might cause seizures (4,5,6,12868).”

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

    4 sources cited
    1. 4. Newall CA, Anderson LA, Philpson JD. Herbal Medicine: A Guide for Healthcare Professionals. London, UK: The Pharmaceutical Press, 1996.
    2. 5. Foster S, Tyler VE. Tyler's Honest Herbal: A Sensible Guide to the Use of Herbs and Related Remedies. 3rd ed., Binghamton, NY: Haworth Herbal Press, 1993.
    3. 6. The Review of Natural Products by Facts and Comparisons. St. Louis, MO: Wolters Kluwer Co., 1999.
    4. 12868. Burkhard PR, Burkhardt K, Haenggeli CA, Landis T. Plant-induced seizures: reappearance of an old problem. J Neurol 1999;246:667-70. PubMed

    Metronidazole

    Listed in the ADVERSE REACTIONS section of the FDA label for Metronidazole. Read the label on DailyMed ›

  • An allergic reaction Worth acting on reported in 4.9% of FDA reports for Metronidazole Additional detail

    Rosemary

    “Topically, allergic reactions can occur. When used in the mouth, lip and gum edema have occurred. When used on the skin, allergic contact dermatitis has occurred, likely due to the constituent carnosol.

    Rosemary might also cause occupational asthma. A case of occupational asthma caused by several aromatic herbs including thyme, rosemary, bay leaf, and garlic has been reported.”

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

    2 sources cited
    1. 101173. Valones MAA, Silva ICG, Gueiros LAM, Leão JC, Caldas AF Jr, Carvalho AAT. Clinical assessment of rosemary-based toothpaste (Rosmarinus officinalis Linn.): A randomized controlled double-blind study. Braz Dent J. 2019;30(2):146-151. PubMed
    2. 783. Cartier LC, Lehrer A, Malo JL. Occupational asthma caused by aromatic herbs. Allergy 1996;51:647-9. DOI

    Metronidazole

    Listed in the ADVERSE REACTIONS section of the FDA label for Metronidazole, and in voluntary FDA adverse-event reports. Read the label on DailyMed ›

  • A skin rash Additional detail

    Rosemary

    “Topically, rosemary use can lead to photosensitivity, erythema, dermatitis, and cheilitis in hypersensitive individuals (4,6).”

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

    2 sources cited
    1. 4. Newall CA, Anderson LA, Philpson JD. Herbal Medicine: A Guide for Healthcare Professionals. London, UK: The Pharmaceutical Press, 1996.
    2. 6. The Review of Natural Products by Facts and Comparisons. St. Louis, MO: Wolters Kluwer Co., 1999.

    Metronidazole

    Listed in the ADVERSE REACTIONS section of the FDA label for Metronidazole. Read the label on DailyMed ›

Reported for Rosemary but not commonly for Metronidazole: sun sensitivity, wheezing and swelling.

Effects for Metronidazole come from the ADVERSE REACTIONS section of its FDA label; effects for Rosemary come from the Natural Medicines adverse-effect record, quoted above. Where a percentage is shown, it is the share of 64,630 voluntary FDA FAERS reports for Metronidazole that mention that effect — a reporting proportion, not an incidence rate and not evidence the drug caused it. Wording is matched across sources by our own clinical vocabulary, so treat this as a prompt to pay attention, not a diagnosis.

Special populations

Rosemary in Pregnancy & Breastfeeding

Pregnancy Possibly Unsafe

When used orally in medicinal amounts. Rosemary might have uterine and menstrual flow stimulant effects, and might increase metabolism of estradiol and estrone; avoid using. There is insufficient reliable information available about the safety of rosemary when used topically during pregnancy.

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

From our Q&A

Questions About Rosemary or Metronidazole

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Rosemary or Metronidazole, 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 Metronidazole

This page covers Rosemary only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Metronidazole page lists 83 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), American Hellebore (major), Arsenic (major), Cesium (major) and Ephedra (major).

By severity: 7 major · 63 moderate · 13 minor.

From our pharmacist’s overview on the Metronidazole page

“Metronidazole (Flagyl) can stretch the heart's QT interval on its own, and most of the seven major-rated interactions among its 83 flagged supplement ingredients do the same thing, so I read this list with more wariness than most antibiotics earn. Grapefruit and ephedra stand out for adding to that heart-rhythm risk, while activated ch…”

Reviewed by 2 · Jul 18, 2026

Open the Metronidazole interaction page

One more smart check

Taking Rosemary as Part of a Dietary Supplement Product? Check It for Interactions

We hold 1,786 real supplement products containing Rosemary, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Rosemary. Even though Rosemary itself has no known interaction with Metronidazole, 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 Rosemary and Metronidazole 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 Rosemary
Top 25%

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

29 days ago today
Medication Metronidazole
Top 25%

#329 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 Rosemary reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 20, 2026. The Rosemary and Metronidazole 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 Rosemary

What is Rosemary?

Rosemary
  • Memory and concentration
  • Digestive upset
  • Hair growth
  • Anxiety and stress (aromatherapy)
  • Muscle and joint discomfort
  • Antioxidant support

Rosemary is a fragrant Mediterranean herb that is safe and flavorful in normal food amounts. Some early research suggests possible benefits for memory, mood, and hair growth, but the evidence is limited and far from conclusive. Concentrated supplements and the essential oil should be used carefully, and the essential oil should never be swallowed.

Rosmarinus officinalis · Lamiaceae · Leaves and essential oil · Culinary herb, tea, capsules, dried leaf extract, essential oil (for aromatherapy and topical use)

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

Rosemary: dosing

There is no well-established standardized dose for rosemary as a supplement. Amounts used in studies have varied widely depending on the form (tea, extract, or aromatherapy).If you use a rosemary supplement, follow the directions on the product label and do not exceed the recommended amount.

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

Read the full Rosemary monograph & all interactions
Medication

About Metronidazole

What Is Metronidazole Used For?

Brand names: Flagyl, Protostat, Metronidazole, Nidazol, Trikacide, MetroGel, Flagyl IV, Metronidazole Redi-Infusion, Flagyl IV RTU, Metro IV, Anabact, Metrosa, Metrotop, Noritate, Rozex Cream, Rozex Gel, Zyomet, Likmez

Metronidazole treats three main types of infections. It's used for trichomoniasis (a sexually transmitted parasitic infection), amebiasis (an intestinal or liver infection caused by a parasite), and serious anaerobic bacterial infections — infections caused by bacteria that thrive without oxygen, which can affect the abdomen, skin, bones, lungs, and other areas.

Because sexual partners can pass trichomoniasis back and forth, both partners are typically treated at the same time, even if one has no symptoms.

Most-Reported Side Effects for Metronidazole

From FAERS, the FDA’s public side-effect reporting system (64,630 reports, all brands). Reports are voluntary and are not proof the drug caused the effect.

Nausea 4,812 reports
Diarrhea 4,197 reports
Vomiting 3,393 reports
Fever 3,294 reports
Drug hypersensitivity 3,160 reports
See full Metronidazole drug information
Keep checking

Other Drugs & Rosemary

Browse every other medication we’ve checked against Rosemary — both the ones with a known interaction and the ones without. Select any drug for the full detail.

0Major
212Moderate
160Minor
2,457No known interaction
212 Moderate 160 Minor 2,457 No interaction
Moderate

212 interactions

Showing 60 of 212 moderate interactions — see all 212 on the Rosemary page.

Minor

160 interactions

Showing 60 of 160 minor interactions — see all 160 on the Rosemary page.

No interaction 2,457 drugs checked — show the list

We also checked Rosemary against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 2,457 medications checked with no known interaction — see the full Rosemary list.

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

Rosemary References

The 20 references that drive our Rosemary 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. Newall CA, Anderson LA, Philpson JD. Herbal Medicine: A Guide for Healthcare Professionals. London, UK: The Pharmaceutical Press, 1996.
  2. Foster S, Tyler VE. Tyler's Honest Herbal: A Sensible Guide to the Use of Herbs and Related Remedies. 3rd ed., Binghamton, NY: Haworth Herbal Press, 1993.
  3. The Review of Natural Products by Facts and Comparisons. St. Louis, MO: Wolters Kluwer Co., 1999.
  4. McGuffin M, Hobbs C, Upton R, Goldberg A, eds. American Herbal Products Association's Botanical Safety Handbook. Boca Raton, FL: CRC Press, LLC 1997.
  5. Gruenwald J, Brendler T, Jaenicke C. PDR for Herbal Medicines. 1st ed. Montvale, NJ: Medical Economics Company, Inc., 1998.
  6. Cartier LC, Lehrer A, Malo JL. Occupational asthma caused by aromatic herbs. Allergy 1996;51:647-9. DOI
  7. Burkhard PR, Burkhardt K, Haenggeli CA, Landis T. Plant-induced seizures: reappearance of an old problem. J Neurol 1999;246:667-70. PubMed
  8. Swain AR, Dutton SP, Truswell AS. Salicylates in foods. J Am Diet.Assoc 1985;85(8):950-60. DOI
  9. Zhu BT, Loder DP, Cai MX, et al. Dietary administration of an extract from rosemary leaves enhances the liver microsomal metabolism of endogenous estrogens and decreases their uterotropic action in CD-1 mice. Carcinogenesis 1998;19(10):1821-7. PubMed
  10. Debersac P, Heydel JM, Amiot MJ, et al. Induction of cytochrome P450 and/or detoxication enzymes by various extracts of rosemary: description of specific patterns. Food Chem Toxicol 2001;39(9):907-18. PubMed
  11. Debersac P, Vernevaut MF, Amiot MJ, et al. Effects of a water-soluble extract of rosemary and its purified component rosmarinic acid on xenobiotic-metabolizing enzymes in rat liver. Food Chem Toxicol 2001;39(2):109-17. PubMed
  12. Lee JJ, Jin YR, Lee JH, et al. Antiplatelet activity of carnosic acid, a phenolic diterpene from Rosmarinus officinalis. Planta Med 2007;73(2):121-7.
  13. Yamamoto J, Yamada K, Naemura A, et al. Testing various herbs for antithrombotic effect. Nutrition 2005;21(5):580-7. PubMed
  14. Naemura A, Ura M, Yamashita T, et al. Long-term intake of rosemary and common thyme herbs inhibits experimental thrombosis without prolongation of bleeding time. Thromb Res 2008;122(4):517-22. PubMed
  15. Lee JJ, Jin YR, Lim Y, et al. Antiplatelet activity of carnosol is mediated by the inhibition of TXA2 receptor and cytosolic calcium mobilization. Vascul Pharmacol 2006;45:148-53. 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 Rosemary and Metronidazole Together: Common Questions

Is it safe to take Rosemary with Metronidazole?
We do not list a known interaction between Rosemary and Metronidazole. 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.
Do Rosemary and Metronidazole have any of the same side effects?
Yes — our sources link each of them separately to 3 of the same effects. That is not an interaction: neither changes how your body handles the other. It does mean that if one of those effects turns up, it can be harder to tell which one is behind it. They are listed on this page with the source behind each.
How was the Rosemary and Metronidazole combination checked?
Interactions in our licensed database are recorded against drug classes. Metronidazole is filed under 8 classifications, and Rosemary has documented interactions with 6 drug classes — none of Metronidazole'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 Rosemary interact with any other medications?
Yes. Rosemary has 372 documented drug interactions in our database — Metronidazole 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 Metronidazole interact with any supplements?
Yes. Metronidazole has documented interactions with 83 supplements in our database — Rosemary is not one of them. The Metronidazole 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

Rosemary monograph Uses, safety profile, and every drug interaction in one place Metronidazole drug information The full plain-English guide to this medication Metronidazole supplement interactions Every supplement checked against Metronidazole, 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 20 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Metronidazole and Rosemary?

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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.