Drug & supplement interaction

Hawthorn + 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 Hawthorn 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.

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Interaction report

Hawthorn 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 Hawthorn 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.

Hawthorn safety at a glance

Hawthorn overall Use caution Generally well tolerated in studies, but heart conditions need medical supervision.
Pregnancy Avoid Not enough safety information; avoid use during pregnancy.
Breastfeeding Avoid Not enough safety information; avoid while breastfeeding.

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

Still wondering about combining Letrozole and Hawthorn? 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. Hawthorn has documented interactions with 6 drug classes — the most serious being nitrates (major), phosphodiesterase-5 inhibitors (major) and anticoagulant/antiplatelet drugs (moderate) — 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

Hawthorn Does Interact With Other Medications

Hawthorn has 14 major, 177 moderate known drug interactions in our database — Letrozole isn’t one of them. If you take anything else, check it against the full list below.

Major 14 Moderate 177 No known interaction 2,639 (incl. Letrozole)
Taking anything else?

Check Another of Your Medications Against Hawthorn

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

What to actually watch for

No Interaction Found — But Data Suggests Hawthorn and Letrozole 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. One of them is worth acting on rather than waiting out — marked below.

  • Bleeding or bruising Worth acting on Additional detail

    Hawthorn

    “Orally, rare abdominal discomfort of uncertain relationship to hawthorn has been reported in a large clinical trial, surveillance study, case reports, and a literature review. Digestive intolerance, diarrhea, flatulence, gastroenteritis, increased bowel movements, obstipation, mild and rare nausea, vomiting, nutritional and metabolic problems, and other non-specific gastrointestinal effects, have also been reported.”

    Hawthorn · Natural Medicines adverse-effect record, reported in congestive heart failure (chf).

    6 sources cited
    1. 19241. Dalli E, Colomer E, Tormos MC, et al. Crataegus laevigata decreases neutrophil elastase and has hypolipidemic effect: a randomized, double-blind, placebo-controlled trial. Phytomedicine. 6-15-2011;18:769-75. PubMed
    2. 19243. Maek-a-nantawat W, Phonrat B, Dhitavat J, et al. Safety and efficacy of CKBM-A01, a Chinese herbal medicine, among asymptomatic HIV patients. Southeast Asian J Trop.Med Public Health 2009;40:494-501.
    3. 113112. Palmer KG, Lebin JA, Cronin MT, Mazor SS, Burns RA. Crataegus mexicana (Tejocote) Exposure Associated with Cardiotoxicity and a Falsely Elevated Digoxin Level. J Med Toxicol. 2019;15(4):295-298. PubMed
    4. 8281. Tauchert M. Efficacy and safety of crataegus extract WS 1442 in comparison with placebo in patients with chronic stable New York Heart Association class-III heart failure. Am Heart J 2002;143:910-5. PubMed
    5. 10144. Pittler MH, Schmidt K, Ernst E. Hawthorn extract for treating chronic heart failure: meta-analysis of randomized trials. Am J Med 2003;114:665-74.. PubMed
    6. 19247. Daniele C, Mazzanti G, Pittler MH, et al. Adverse-event profile of Crataegus spp.: a systematic review. Drug Saf 2006;29:523-35. PubMed

    “Flu-like syndrome and other non-specific infections have been reported following the use of the hawthorn extract WS 1442. Hawthorn has also been reported to cause nosebleeds.”

    Hawthorn · Natural Medicines adverse-effect record, reported in influenza.

    4 sources cited
    1. 8281. Tauchert M. Efficacy and safety of crataegus extract WS 1442 in comparison with placebo in patients with chronic stable New York Heart Association class-III heart failure. Am Heart J 2002;143:910-5. PubMed
    2. 17203. Holubarsch CJ, Colucci WS, Meinertz T, et al. The efficacy and safety of Crataegus extract WS 1442 in patients with heart failure: the SPICE trial. Eur J Heart Fail 2008;10:1255-63. PubMed
    3. 19222. Zick SM, Vautaw BM, Gillespie B, Aaronson KD. Hawthorn Extract Randomized Blinded Chronic Heart Failure (HERB CHF) trial. Eur J Heart Fail. 2009;11:990-99. PubMed
    4. 10144. Pittler MH, Schmidt K, Ernst E. Hawthorn extract for treating chronic heart failure: meta-analysis of randomized trials. Am J Med 2003;114:665-74.. PubMed

    Letrozole

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

  • Joint pain / Muscle pain Additional detail

    Hawthorn

    “In clinical trials, arthritis, back pain, weakness, and other non-specific musculoskeletal effects have been reported following the use of various hawthorn preparations (e.g. WS 1442, CKBM-A01). Additionally, in a case report, myalgia has been reported following use of hawthorn root extract.”

    Hawthorn · Natural Medicines adverse-effect record, reported in back pain.

    4 sources cited
    1. 8281. Tauchert M. Efficacy and safety of crataegus extract WS 1442 in comparison with placebo in patients with chronic stable New York Heart Association class-III heart failure. Am Heart J 2002;143:910-5. PubMed
    2. 19243. Maek-a-nantawat W, Phonrat B, Dhitavat J, et al. Safety and efficacy of CKBM-A01, a Chinese herbal medicine, among asymptomatic HIV patients. Southeast Asian J Trop.Med Public Health 2009;40:494-501.
    3. 19222. Zick SM, Vautaw BM, Gillespie B, Aaronson KD. Hawthorn Extract Randomized Blinded Chronic Heart Failure (HERB CHF) trial. Eur J Heart Fail. 2009;11:990-99. PubMed
    4. 113113. Espinosa J, Bassett R, Lucerna A, Finn D. Hawthorne root (Crataegus mexicana) toxicity. Am J Emerg Med. 2024;78:242.e5-242.e6. PubMed

    Letrozole

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

  • Dizziness / Headache Additional detail

    Hawthorn

    “Orally, headache and dizziness/vertigo were reported in 2 patients in a large surveillance trial of 3,664 patients with cardiac failure, in 15 patients with CHF as reported in a literature review of 5,577 patients, in a varying number of clinical trial participants, and in case reports. Incidences of fainting, fever, and infrequent, mild and transient sleepiness have also been reported.”

    Hawthorn · Natural Medicines adverse-effect record, reported in cluster headache.

    6 sources cited
    1. 54692. Loew D, Albrecht M, and Podzuweit H. Efficacy and tolerability of a Hawthorn preparation in patients with heart failure Stage I and II according to NYHA - a surveillance study. Phytomedicine 1996;3(Suppl 1):92.
    2. 19247. Daniele C, Mazzanti G, Pittler MH, et al. Adverse-event profile of Crataegus spp.: a systematic review. Drug Saf 2006;29:523-35. PubMed
    3. 8281. Tauchert M. Efficacy and safety of crataegus extract WS 1442 in comparison with placebo in patients with chronic stable New York Heart Association class-III heart failure. Am Heart J 2002;143:910-5. PubMed
    4. 19222. Zick SM, Vautaw BM, Gillespie B, Aaronson KD. Hawthorn Extract Randomized Blinded Chronic Heart Failure (HERB CHF) trial. Eur J Heart Fail. 2009;11:990-99. PubMed
    5. 19244. Asher GN, Viera AJ, Weaver MA, et al. Effect of hawthorn standardized extract on flow mediated dilation in prehypertensive and mildly hypertensive adults: a randomized, controlled cross-over trial. BMC.Complement Altern.Med 2012;12:26. PubMed
    6. 113112. Palmer KG, Lebin JA, Cronin MT, Mazor SS, Burns RA. Crataegus mexicana (Tejocote) Exposure Associated with Cardiotoxicity and a Falsely Elevated Digoxin Level. J Med Toxicol. 2019;15(4):295-298. PubMed

    Letrozole

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

  • Nausea Additional detail

    Hawthorn

    Recorded for Hawthorn in the same Natural Medicines adverse-effect record shown under Bleeding or bruising above.

    Letrozole

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

Reported for Hawthorn but not commonly for Letrozole: diarrhea, heart failure, stomach upset and an irregular heartbeat.

Effects for Letrozole come from the ADVERSE REACTIONS section of its FDA label; effects for Hawthorn 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.

From our Q&A

Questions About Hawthorn 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 Hawthorn 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 Hawthorn 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 Hawthorn as Part of a Dietary Supplement Product? Check It for Interactions

We hold 2,624 real supplement products containing Hawthorn, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Hawthorn. Even though Hawthorn 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 Hawthorn 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 Hawthorn
Top 10%

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

29 days ago today
Medication Letrozole
Top 5%

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

What is Hawthorn?

Hawthorn
  • Heart failure symptoms
  • High blood pressure
  • Chest pain (angina)
  • Irregular heartbeat
  • Digestive upset
  • Anxiety

Hawthorn is a plant traditionally used for heart-related complaints, and some studies suggest it may modestly help symptoms of mild heart failure when added to standard care. However, the evidence is mixed and it should never replace prescribed heart medicines. Always talk to your pharmacist or doctor before using hawthorn, especially if you have a heart condition.

Crataegus monogyna · Rosaceae · Leaves, flowers, and berries (fruit) · Capsules, tablets, standardized extracts, liquid tinctures, teas

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

Hawthorn: dosing

There is no single standard dose of hawthorn that fits everyone. This is especially important if you take heart or blood pressure medicines or have any chronic health condition. Do not assume that more is better.

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

Read the full Hawthorn 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 & Hawthorn

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

14Major
177Moderate
0Minor
2,638No known interaction
14 Major 177 Moderate 2,638 No interaction
Major

14 interactions

Moderate

177 interactions

Showing 60 of 177 moderate interactions — see all 177 on the Hawthorn page.

No interaction 2,638 drugs checked — show the list

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

Showing the 60 most looked-up of 2,638 medications checked with no known interaction — see the full Hawthorn list.

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

Hawthorn References

The 25 references that drive our Hawthorn 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. Tauchert M. Efficacy and safety of crataegus extract WS 1442 in comparison with placebo in patients with chronic stable New York Heart Association class-III heart failure. Am Heart J 2002;143:910-5. PubMed
  2. Pittler MH, Schmidt K, Ernst E. Hawthorn extract for treating chronic heart failure: meta-analysis of randomized trials. Am J Med 2003;114:665-74.. PubMed
  3. Chang Q, Zuo Z, Harrison F, Chow MS. Hawthorn. J Clin Pharmacol 2002;42:605-12.
  4. Holubarsch CJ, Colucci WS, Meinertz T, et al. The efficacy and safety of Crataegus extract WS 1442 in patients with heart failure: the SPICE trial. Eur J Heart Fail 2008;10:1255-63. PubMed
  5. Pittler MH, Guo R, and Ernst E. Hawthorn extract for treating chronic heart failure. Cochrane.Database.Syst Rev 2008:CD005312. PubMed
  6. Zick SM, Vautaw BM, Gillespie B, Aaronson KD. Hawthorn Extract Randomized Blinded Chronic Heart Failure (HERB CHF) trial. Eur J Heart Fail. 2009;11:990-99. PubMed
  7. Werner NS, Duschek S, and Schandry R. D-camphor-crataegus berry extract combination increases blood pressure and cognitive functioning in the elderly - a randomized, placebo controlled double blind study. Phytomedicine. 2009;16:1077-82. PubMed
  8. Dalli E, Colomer E, Tormos MC, et al. Crataegus laevigata decreases neutrophil elastase and has hypolipidemic effect: a randomized, double-blind, placebo-controlled trial. Phytomedicine. 6-15-2011;18:769-75. PubMed
  9. Maek-a-nantawat W, Phonrat B, Dhitavat J, et al. Safety and efficacy of CKBM-A01, a Chinese herbal medicine, among asymptomatic HIV patients. Southeast Asian J Trop.Med Public Health 2009;40:494-501.
  10. Asher GN, Viera AJ, Weaver MA, et al. Effect of hawthorn standardized extract on flow mediated dilation in prehypertensive and mildly hypertensive adults: a randomized, controlled cross-over trial. BMC.Complement Altern.Med 2012;12:26. PubMed
  11. Walker AF, Marakis G, Simpson E, et al. Hypotensive effects of hawthorn for patients with diabetes taking prescription drugs: a randomised controlled trial. Br J Gen.Pract 2006;56:437-43.
  12. Daniele C, Mazzanti G, Pittler MH, et al. Adverse-event profile of Crataegus spp.: a systematic review. Drug Saf 2006;29:523-35. PubMed
  13. Tankanow R, Tamer HR, Streetman DS, et al. Interaction study between digoxin and a preparation of hawthorn (Crataegus oxyacantha). J.Clin.Pharmacol. 2003;43:637-42. DOI
  14. Tauchert, M., Gildor, A., and Lipinski, J. [High-dose Crataegus extract WS 1442 in the treatment of NYHA stage II heart failure]. Herz 1999;24(6):465-474.
  15. Horoz, M., Gok, E., Genctoy, G., Ozcan, T., Olmaz, R., Akca, M., Kiykim, A., and Gurses, I. Crataegus orientalis associated multiorgan hypersensitivity reaction and acute renal failure. Intern.Med 2008;47(23):2039-2042. 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 Hawthorn and Letrozole Together: Common Questions

Is it safe to take Hawthorn with Letrozole?
We do not list a known interaction between Hawthorn 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 Hawthorn and Letrozole have any of the same side effects?
Yes — our sources link each of them separately to 6 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 Hawthorn and Letrozole combination checked?
Interactions in our licensed database are recorded against drug classes. Letrozole is filed under 4 classifications, and Hawthorn has documented interactions with 6 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 Hawthorn interact with any other medications?
Yes. Hawthorn has 191 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 — Hawthorn 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

Hawthorn 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 25 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Letrozole and Hawthorn?

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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.