Drug & supplement interaction

Eastern Hemlock + 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 Eastern Hemlock 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.

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

Eastern Hemlock 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 Eastern Hemlock 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.

Worth understanding: our licensed dataset holds no drug-interaction record for Eastern Hemlock at all — not against Letrozole, and not against any other medication we track. This verdict therefore rests on the absence of any recorded data, not on research that looked at this combination and found nothing. We cannot rule an interaction out.

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.

Eastern Hemlock safety at a glance

Eastern Hemlock overall Use caution Little modern safety data exists, and the essential oil can be irritating, so use carefully.
Pregnancy Avoid Not enough safety information is available, so it is best avoided.
Breastfeeding Avoid Safety has not been studied, so avoid use while breastfeeding.

Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Still wondering about combining Letrozole and Eastern Hemlock? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
What to actually watch for

What Eastern Hemlock Itself Has Been Linked To

This is not an interaction — nothing below involves Letrozole. It is the side-effect record for Eastern Hemlock on its own, from the licensed Natural Medicines monograph. If something new turns up after you add Eastern Hemlock, this list is the first place to look. 2 entries are worth acting on rather than waiting out — marked below.

  • Kidney problems Worth acting on Additional detail

    “Orally, no adverse effects have been reported. However, a thorough evaluation of safety outcomes has not been conducted. Eastern hemlock bark is rich in tannins. Plants with at least 10% tannins may cause gastrointestinal disturbances, kidney damage, and necrotic conditions of the liver.”

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

    2 sources cited
    1. 12. McGuffin M, Hobbs C, Upton R, Goldberg A, eds. American Herbal Products Association's Botanical Safety Handbook. Boca Raton, FL: CRC Press, LLC 1997.
    2. 48525. Mitchell, J. C. Patch test results - screening set and plants. Contact Dermatitis Newsletter 1970;8:177.
  • An allergic reaction Worth acting on Additional detail

    “Topically, allergic reaction to eastern hemlock has been rarely reported. In a study of 125 forest workers, one developed contact dermatitis. The individual showed a positive patch test reaction to an extract of Eastern hemlock.”

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

    1 source cited
    1. 48525. Mitchell, J. C. Patch test results - screening set and plants. Contact Dermatitis Newsletter 1970;8:177.
  • Stomach upset Additional detail

    Recorded for Eastern Hemlock in the same Natural Medicines adverse-effect record shown under Kidney problems above.

  • A skin rash Additional detail

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

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

From our Q&A

Questions About Eastern Hemlock 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 Eastern Hemlock 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 Eastern Hemlock 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

How much people look this up

Where Eastern Hemlock 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 Eastern Hemlock
Steady interest

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

29 days ago today
Medication Letrozole
Top 5%

#48 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 Eastern Hemlock reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 13, 2026. The Eastern Hemlock and Letrozole records this page draws on were last updated July 10, 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 Eastern Hemlock

What is Eastern Hemlock?

  • Coughs and colds
  • Sore throat
  • Wound care
  • Vitamin C source (needle tea)
  • Aches and pains (topical)

Eastern Hemlock is an evergreen conifer tree (Tsuga canadensis) traditionally used by Native Americans and early settlers for coughs, sore throats, and as a vitamin C-rich tea. There is very little modern scientific evidence to support any of these uses, and it should not be confused with poison hemlock. Talk to a pharmacist or doctor before using it, and avoid it during pregnancy and breastfeeding.

Tsuga canadensis · Pinaceae · Inner bark, needles (leaves), young twigs, and resin · Tea, tincture, essential oil, salve, and bark extract

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

Eastern Hemlock: dosing

There is no established or standardized dose for Eastern Hemlock. It has not been studied enough to know a safe and effective amount for any condition.If you choose to use a commercial product, follow the directions on the label exactly and do not exceed them. Essential oils should be used only as directed for external use and kept away from the eyes, mouth, and children.

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

Read the full Eastern Hemlock 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 & Eastern Hemlock

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

0Major
0Moderate
0Minor
2,829No known interaction
2,829 No interaction
No interaction 2,829 drugs checked — show the list

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

Showing the 60 most looked-up of 2,829 medications checked with no known interaction — see the full Eastern Hemlock list.

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

Eastern Hemlock References

The 2 references that drive our Eastern Hemlock 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. McGuffin M, Hobbs C, Upton R, Goldberg A, eds. American Herbal Products Association's Botanical Safety Handbook. Boca Raton, FL: CRC Press, LLC 1997.
  2. Mitchell, J. C. Patch test results - screening set and plants. Contact Dermatitis Newsletter 1970;8:177.

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 Eastern Hemlock and Letrozole Together: Common Questions

Is it safe to take Eastern Hemlock with Letrozole?
We do not list a known interaction between Eastern Hemlock 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.
Does Letrozole interact with any supplements?
Yes. Letrozole has documented interactions with 142 supplements in our database — Eastern Hemlock 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

Eastern Hemlock 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 2 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Letrozole and Eastern Hemlock?

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.