Drug & supplement interaction

Juniper + Letrozole

Letrozole brand name: Femara.

No Known Interaction
Medically reviewed by · Updated July 2026 · Pair last verified Sep 13, 2026
The bottom line No known interaction

We found no known interaction between Juniper and Letrozole 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.

Know someone taking this? Share
Facebook Post Reddit Email
On this page
Interaction report

Juniper and Letrozole

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 Letrozole and Juniper 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.

Juniper safety at a glance

Juniper overall Use caution Generally tolerated in food amounts, but medicinal doses may irritate the kidneys and should not be used long-term.
Pregnancy Unsafe When used orally. Juniper can increase uterine tone, interfere with fertility and implantation, and cause abortion. Read the full pregnancy detail
Breastfeeding Avoid Not enough safety information, so it is best avoided while breastfeeding.

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 Letrozole and Juniper? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
How we checked

Why No Interaction Is Listed for Letrozole

Interactions in our licensed database are recorded against drug classes, not just single drug names. Letrozole is filed under 4 classifications — including aromatase inhibitors, cytochrome p450 2c19 (cyp2c19) inhibitors, cytochrome p450 3a4 (cyp3a4) substrates. Juniper has documented interactions with 3 drug classes — the most serious being antidiabetes drugs (moderate), diuretic drugs (minor) and lithium (minor) — and none of Letrozole’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

Juniper Does Interact With Other Medications

Juniper has 86 moderate, 76 minor known drug interactions in our database — Letrozole isn’t one of them. If you take anything else, check it against the full list below.

Moderate 86 Minor 76 No known interaction 2,668 (incl. Letrozole)
Taking anything else?

Check Another of Your Medications Against Juniper

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

What to actually watch for

No Interaction Found — But Data Suggests Juniper and Letrozole May Share a Side Effect

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.

  • Swelling Additional detail

    Juniper

    “Topically, juniper can cause skin irritation. Signs of topical poisoning include burning, erythema, inflammation with blisters, and edema (4). Repeated exposure to the juniper pollen can cause occupational allergies that affect the skin (6). In a case report, a 62-year-old woman developed burn-like blistering lesions after carrying juniper in close contact to her skin.”

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

    3 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.
    3. 103756. Tammaro A, Adebanjo GAR, Chello C, et al. Bullous dermatitis caused by common juniper. Contact Dermatitis. 2020. PubMed

    Letrozole

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

Effects for Letrozole come from the ADVERSE REACTIONS section of its FDA label; effects for Juniper come from the Natural Medicines adverse-effect record, quoted above. Wording is matched across sources by our own clinical vocabulary, so treat this as a prompt to pay attention, not a diagnosis.

Special populations

Juniper in Pregnancy & Breastfeeding

Pregnancy Unsafe

When used orally. Juniper can increase uterine tone, interfere with fertility and implantation, and cause abortion.

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 Letrozole Is Prescribed For, and What Juniper Has Been Studied For

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

Letrozole is prescribed for: Letrozole (brand name Femara) is used to treat breast cancer in postmenopausal women whose tumors are driven by estrogen. It is used in three settings: as adjuvant (after-surgery) treatment for hormone receptor positive early breast cancer; as extended adjuvant treatment for women who have already completed about five years of tamoxifen therapy; and as first- or second-line treatment for locally advanced or metastatic (spread) breast cancer. Femara is specifically indicated for first-line treatment of hormone receptor positive or receptor-unknown locally advanced or metastatic breast cancer, and for advanced breast cancer in women whose disease has progressed after antiestrogen therapy.

Juniper has been studied for:

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

    Juniper for cancer

    Although there has been interest in using oral juniper for cancer, there is insufficient reliable information about the clinical effects of juniper 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 Letrozole on your own; if you are taking Juniper for the same health topic, tell your prescriber, especially if the medicine is being adjusted to a target.

From our Q&A

Questions About Juniper or Letrozole

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

This page covers Juniper only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Letrozole page lists 142 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Grapefruit (major), St. John's Wort (major), 7-methoxyflavone (moderate) and Acacia Rigidula (moderate).

By severity: 3 major · 99 moderate · 40 minor.

From our pharmacist’s overview on the Letrozole page

“Letrozole (Femara) is prescribed to keep hormone-driven breast cancer from returning, so a supplement that shifts its blood level can quietly undercut treatment. Give this list of 142 ingredients genuine respect, and learn the three major entries first.”

Reviewed by 2 · Jul 18, 2026

Open the Letrozole interaction page

One more smart check

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

We hold 1,100 real supplement products containing Juniper, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Juniper. Even though Juniper itself has no known interaction with Letrozole, 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 Juniper and Letrozole 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 Juniper
Top 25%

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

29 days ago today
Medication Letrozole
Top 5%

#51 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 Juniper reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 13, 2026. The Juniper and Letrozole 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 Juniper

What is Juniper?

  • Water retention (diuretic)
  • Digestive upset and bloating
  • Urinary tract support
  • Joint and muscle discomfort
  • Flavoring (gin and food)

Juniper berry is a traditional herb best known for flavoring gin and for its folk use as a diuretic and digestive aid. Solid human evidence for its health benefits is limited, and it can irritate the kidneys with high doses or long-term use. Pregnant people and those with kidney problems should avoid it, and everyone should check with a pharmacist or doctor first.

Juniperus communis · Cupressaceae · Berries (ripe cones) and essential oil · Tea, capsules, tincture, essential oil, dried berries

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

Juniper: dosing

There is no well-established standard dose for juniper, and the right amount depends on the form (tea, capsule, tincture, or oil). Because of the risk of kidney irritation, experts generally advise against high doses or use longer than a few weeks.If you choose to use a juniper product, follow the directions on the label and do not exceed the recommended amount. Never take juniper essential oil by mouth without professional guidance.

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

Read the full Juniper monograph & all interactions
Medication

About Letrozole

What Is Letrozole Used For?

Brand name: Femara

Letrozole (brand name Femara) is used to treat breast cancer in postmenopausal women whose tumors are driven by estrogen. It is used in three settings: as adjuvant (after-surgery) treatment for hormone receptor positive early breast cancer; as extended adjuvant treatment for women who have already completed about five years of tamoxifen therapy; and as first- or second-line treatment for locally advanced or metastatic (spread) breast cancer.

Femara is specifically indicated for first-line treatment of hormone receptor positive or receptor-unknown locally advanced or metastatic breast cancer, and for advanced breast cancer in women whose disease has progressed after antiestrogen therapy.

See full Letrozole drug information
Keep checking

Other Drugs & Juniper

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

0Major
86Moderate
76Minor
2,667No known interaction
86 Moderate 76 Minor 2,667 No interaction
Moderate

86 interactions

Showing 60 of 86 moderate interactions — see all 86 on the Juniper page.

Minor

76 interactions

Showing 60 of 76 minor interactions — see all 76 on the Juniper page.

No interaction 2,667 drugs checked — show the list

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

Showing the 60 most looked-up of 2,667 medications checked with no known interaction — see the full Juniper list.

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

Juniper References

The 7 references that drive our Juniper 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. The Review of Natural Products by Facts and Comparisons. St. Louis, MO: Wolters Kluwer Co., 1999.
  3. Brinker F. Herb Contraindications and Drug Interactions. 2nd ed. Sandy, OR: Eclectic Medical Publications, 1998.
  4. Robbers JE, Tyler VE. Tyler's Herbs of Choice: The Therapeutic Use of Phytomedicinals. New York, NY: The Haworth Herbal Press, 1999.
  5. Sanchez de Medina F, Gamez MJ, Jimenez I, et al. Hypoglycemic activity of juniper "berries." Planta Med 1994;60:197-200. PubMed
  6. Swanston-Flatt SK, Day C, Bailey CJ, Flatt PR. Traditional plant treatments for diabetes. Studies in normal and streptozotocin diabetic mice. Diabetologia 1990;33:462-4. PubMed
  7. Tammaro A, Adebanjo GAR, Chello C, et al. Bullous dermatitis caused by common juniper. Contact Dermatitis. 2020. 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 Juniper and Letrozole Together: Common Questions

Is it safe to take Juniper with Letrozole?
We do not list a known interaction between Juniper and Letrozole. 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 Juniper and Letrozole have any of the same side effects?
Yes — our sources link each of them separately to one 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.
Are Juniper and Letrozole 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 Juniper in each. That is a conversation for your prescriber, especially if Letrozole is being adjusted to a target.
How was the Juniper and Letrozole combination checked?
Interactions in our licensed database are recorded against drug classes. Letrozole is filed under 4 classifications, and Juniper has documented interactions with 3 drug classes — none of Letrozole'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 Juniper interact with any other medications?
Yes. Juniper has 162 documented drug interactions in our database — Letrozole 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 Letrozole interact with any supplements?
Yes. Letrozole has documented interactions with 142 supplements in our database — Juniper is not one of them. The Letrozole 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

Juniper monograph Uses, safety profile, and every drug interaction in one place Letrozole drug information The full plain-English guide to this medication Letrozole supplement interactions Every supplement checked against Letrozole, 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 7 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Letrozole and Juniper?

Our pharmacists answer your medication & supplement questions — free.

Ask a pharmacist

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.