Drug & supplement interaction

Maitake Mushroom + 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 Maitake Mushroom 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

Maitake Mushroom 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 Maitake Mushroom 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.

Maitake Mushroom safety at a glance

Maitake Mushroom overall Use caution Generally well tolerated as food, but supplement safety has not been fully studied.
Pregnancy Avoid Not enough safety data, so concentrated supplements should be avoided during pregnancy.
Breastfeeding Avoid Not enough safety data, so concentrated supplements should be avoided while breastfeeding.

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

Still wondering about combining Letrozole and Maitake Mushroom? 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. Maitake Mushroom has documented interactions with 3 drug classes — the most serious being antidiabetes drugs (moderate), antihypertensive drugs (moderate) and warfarin (coumadin) (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

Maitake Mushroom Does Interact With Other Medications

Maitake Mushroom has 260 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.

Moderate 260 No known interaction 2,570 (incl. Letrozole)
Taking anything else?

Check Another of Your Medications Against Maitake Mushroom

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

What to actually watch for

No Interaction Found — But Data Suggests Maitake Mushroom 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.

  • Nausea Additional detail

    Maitake Mushroom

    “In clinical research of a polysaccharide extract from maitake mushroom, one patient reported nausea and 2 out of 26 reported epigastric pain. In a clinical trial of a liquid extract from maitake mushroom, 2 out of 21 patients experienced diarrhea, and one experienced nausea. One patient withdrew from the study due to diarrhea.”

    Maitake Mushroom · Natural Medicines adverse-effect record, reported in diarrhea.

    3 sources cited
    1. 61239. Deng, G., Lin, H., Seidman, A., Fornier, M., D'Andrea, G., Wesa, K., Yeung, S., Cunningham-Rundles, S., Vickers, A. J., and Cassileth, B. A phase I/II trial of a polysaccharide extract from Grifola frondosa (Maitake mushroom) in breast cancer patients: i
    2. 17131. Chen JT, Tominaga K, Sato Y, et al. Maitake mushroom (Grifola frondosa) extract induces ovulation in patients with polycystic ovary syndrome: a possible monotherapy and a combination therapy after failure with first-line clomiphene citrate. J Altern Compl
    3. 92843. Wesa KM, Cunningham-Rundles S, Klimek VM, et al. Maitake mushroom extract in myelodysplastic syndromes (MDS): a phase II study. Cancer Immunol Immunother 2015;64(2):237-47. PubMed

    Letrozole

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

Reported for Maitake Mushroom but not commonly for Letrozole: an allergic reaction, diarrhea, itching and a skin rash.

Effects for Letrozole come from the ADVERSE REACTIONS section of its FDA label; effects for Maitake Mushroom 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 Maitake Mushroom 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 Maitake Mushroom 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 Maitake Mushroom 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 Maitake Mushroom as Part of a Dietary Supplement Product? Check It for Interactions

We hold 1,788 real supplement products containing Maitake Mushroom, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Maitake Mushroom. Even though Maitake Mushroom 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 Maitake Mushroom 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 Maitake Mushroom
Top 25%

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

What is Maitake Mushroom?

Maitake Mushroom
  • Immune support
  • Blood sugar support in diabetes
  • High blood pressure
  • High cholesterol
  • General wellness and antioxidant support

Maitake is an edible mushroom long used as food and in traditional Japanese medicine, and it is being studied for possible immune, blood sugar, and blood pressure effects. The human evidence is still limited and not strong enough to recommend it as a treatment. It is generally well tolerated as food, but talk to your pharmacist or doctor before using concentrated supplements.

Grifola frondosa · Meripilaceae · Fruiting body (mushroom) and mycelium; also purified extracts such as the 'D-fraction' · Capsules, tablets, powders, liquid extracts (D-fraction/SX-fraction), and whole mushroom used as food

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

Maitake Mushroom: dosing

There is no official, well-established dose for maitake supplements. Products vary widely in strength and in how they are prepared, including whole mushroom powders and standardized extracts like the D-fraction.The best approach is to follow the directions on the product label and to choose products from reputable brands.

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

Read the full Maitake Mushroom 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 & Maitake Mushroom

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

0Major
260Moderate
0Minor
2,569No known interaction
260 Moderate 2,569 No interaction
Moderate

260 interactions

Showing 60 of 260 moderate interactions — see all 260 on the Maitake Mushroom page.

No interaction 2,569 drugs checked — show the list

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

Showing the 60 most looked-up of 2,569 medications checked with no known interaction — see the full Maitake Mushroom list.

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

Maitake Mushroom References

The 8 references that drive our Maitake Mushroom 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. Kabir Y, Kimura S. Dietary mushrooms reduce blood pressure in spontaneously hypertensive rats (SHR). J Nutr Sci Vitaminol (Tokyo) 1989;35:91-4. PubMed
  2. Kabir Y, Yamaguchi M, Kimura S. Effect of shiitake (Lentinus edodes) and maitake (Grifola frondosa) mushrooms on blood pressure and plasma lipids of spontaneously hypertensive rats. J Nutr Sci Vitaminol (Tokyo) 1987;33:341-6. PubMed
  3. Konno S, Tortorelis DG, Fullerton SA, et al. A possible hypoglycaemic effect of maitake mushroom on Type 2 diabetic patients. Diabet Med 2001;18:1010. PubMed
  4. Chen JT, Tominaga K, Sato Y, et al. Maitake mushroom (Grifola frondosa) extract induces ovulation in patients with polycystic ovary syndrome: a possible monotherapy and a combination therapy after failure with first-line clomiphene citrate. J Altern Compl
  5. Hanselin MR, Vande Griend JP, Linnebur SA. INR elevation with maitake extract in combination with warfarin. Ann Pharmacother 2010;44:223-4. PubMed
  6. Talpur, N. A., Echard, B. W., Fan, A. Y., Jaffari, O., Bagchi, D., and Preuss, H. G. Antihypertensive and metabolic effects of whole Maitake mushroom powder and its fractions in two rat strains. Mol.Cell Biochem. 2002;237(1-2):129-136. PubMed
  7. Deng, G., Lin, H., Seidman, A., Fornier, M., D'Andrea, G., Wesa, K., Yeung, S., Cunningham-Rundles, S., Vickers, A. J., and Cassileth, B. A phase I/II trial of a polysaccharide extract from Grifola frondosa (Maitake mushroom) in breast cancer patients: i
  8. Wesa KM, Cunningham-Rundles S, Klimek VM, et al. Maitake mushroom extract in myelodysplastic syndromes (MDS): a phase II study. Cancer Immunol Immunother 2015;64(2):237-47. 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 Maitake Mushroom and Letrozole Together: Common Questions

Is it safe to take Maitake Mushroom with Letrozole?
We do not list a known interaction between Maitake Mushroom 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 Maitake Mushroom 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.
How was the Maitake Mushroom and Letrozole combination checked?
Interactions in our licensed database are recorded against drug classes. Letrozole is filed under 4 classifications, and Maitake Mushroom 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 Maitake Mushroom interact with any other medications?
Yes. Maitake Mushroom has 260 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 — Maitake Mushroom 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

Maitake Mushroom 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 8 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Letrozole and Maitake Mushroom?

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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.