Skip to content

Coming soon. The store is not open yet.

Menu
Full Measure

Ingredient guide

Turkey tail mushroom side effects: what studies report

Written by the Full Measure editorial team, which sells supplements. Approved for publication by the Full Measure owners. Updated .

Drafted with AI assistance from the sources listed below. How we write these

Quick answer

Few side effects have been reported. Healthy adults who took up to 12 g a day of a turkey tail blend for four days had no adverse events, and nine women taking 3 to 9 g a day for six weeks reported mostly mild problems, such as heartburn. Use beyond four months has not been studied in healthy people.1,2

Key facts

  • Four months of turkey tail with an herb did not change liver or kidney tests in 100 healthy adults.3
  • Nausea and stomach upset were not reported in the six-week trial of up to 9 g a day.2
  • A two-week enzyme test found no effect on CYP3A4, which handles many medicines.4
  • Rat tests of a mycelium powder found no toxic or gene-damaging effects.5

What studies report

In a six-week trial of 3, 6 or 9 g a day of mycelium powder in nine women who had just finished radiotherapy for breast cancer, seven of the nine reported events were mild, among them heartburn, constipation and palpitations. Nausea and stomach upset were not reported, and the one severe event was judged unlikely to be related.2

No adverse events were reported in 52 adults who took a two-mushroom mycelium blend including turkey tail at 12 g a day for four days.1

Four months of turkey tail with danshen did not affect liver or kidney blood tests in 100 healthy adults.3

These studies were small, and the longest one in healthy people combined turkey tail with another herb. Rare side effects would not show up in groups this size, so a clean record here is not the same as proof of safety.3

Research in people under cancer care

In seven trials of turkey tail extract given with chemotherapy for bowel cancer, reviewers could not tell which side effects came from the extract and which from the chemotherapy.6

Most of the long-term experience with turkey tail extracts comes from people being treated for cancer, who took PSK for up to three years alongside chemotherapy. If you are in that situation, ask your cancer team before starting it, because they need to know about everything you take.6

Turkey tail and medicines

In 12 healthy adults, 3.6 g a day of the PSP extract for 14 days did not change the activity of CYP3A4, a liver enzyme that clears many medicines. Other drug-handling enzymes were not tested.4

That leaves out medicines cleared by other enzymes or moved by drug transporters, so the study does not cover every medicine.4

None of the official sources we use names turkey tail as interacting with a specific medicine. The warfarin label does ask for more frequent INR checks whenever any herbal product is started or stopped, so tell whoever manages your blood thinner before you begin.7

Animal safety tests

A powder of turkey tail mycelium grown on oats caused no toxic effects in rats at up to 2,000 mg per kg of body weight a day and did not damage genes in laboratory tests. Two of the study's authors worked for the powder's maker.5

Animal tests can flag obvious toxicity, but they cannot show how people will respond over months or years, and this one tested a single maker's powder.5

Claims to be wary of

In March 2026 the FDA warned a seller of turkey tail, chaga and red reishi extracts that citing research on illness to market them made the products unapproved new drugs.8

A supplement may not be sold as a cancer treatment. If a seller makes that kind of claim for a turkey tail product, the FDA regards the product as an unapproved drug.8

Who should ask first

  • Anyone pregnant or breastfeeding
  • People taking a blood thinner, an antiplatelet medicine or a medicine that suppresses the immune system
  • People under cancer care, including chemotherapy, radiotherapy or hormone therapy
  • Anyone allergic to mushrooms or molds

Questions people ask

Is turkey tail mushroom safe to take?

Short studies found few problems, but none followed healthy people for more than four months, so long-term safety is unknown. Ask first if you are pregnant, take a blood thinner or immune-suppressing medicine, or are under cancer care.1,3

Can turkey tail capsules upset your stomach?

In the six-week trial of up to 9 g a day, nausea and stomach upset were not reported, though constipation and heartburn were among the mild events. The four-day blend trial reported no adverse events at all.1,2

Does turkey tail affect the liver or kidneys?

In 100 healthy adults taking turkey tail with an herb for four months, and in 52 adults taking a blend for four days, liver and kidney tests showed no clear change. Longer use has not been studied in healthy people.1,3

See what we make

Every product shows its whole label and what its lab report covers. The store opens soon.

See the Full Measure line

Sources

  1. Saxe G, Smith CN, Golshan S, et al. Polypore mushroom mycelia as an adjunct to COVID-19 vaccination: a randomized clinical trial. BMC Immunol. 2026;27(1):24. Opened 2026-10-07.
  2. Torkelson CJ, Sweet E, Martzen MR, Sasagawa M, Wenner CA, Gay J, Putiri A, Standish LJ. Phase 1 Clinical Trial of Trametes versicolor in Women with Breast Cancer. ISRN Oncol. 2012;2012:251632. Opened 2026-10-07.
  3. Wong CK, Tse PS, Wong EL, Leung PC, Fung KP, Lam CW. Immunomodulatory effects of yun zhi and danshen capsules in health subjects: a randomized, double-blind, placebo-controlled, crossover study. Int Immunopharmacol. 2004;4(2):201-211. Opened 2026-10-07.
  4. Nicandro JP, Tsourounis C, Frassetto L, Guglielmo BJ. In vivo effect of I'm-Yunity on hepatic cytochrome P450 3A4. J Herb Pharmacother. 2007;7(1):39-56. Opened 2026-10-07.
  5. Mahadevan K, Daoust J, Brendler T, Chaudhary A, Saifi A, Garg VK. A toxicological assessment of Hericium erinaceus (Lion's mane) and Trametes versicolor (Turkey tail) mushroom powders. Front Toxicol. 2025;7:1651442. Opened 2026-10-07.
  6. Pilkington K, Wieland LS, Teng L, Jin XY, Storey D, Liu JP. Coriolus (Trametes) versicolor mushroom to reduce adverse effects from chemotherapy or radiotherapy in people with colorectal cancer. Cochrane Database Syst Rev. 2022;11(11):CD012053. Opened 2026-10-07.
  7. Warfarin sodium tablets: prescribing information (A-S Medication Solutions). DailyMed, U.S. National Library of Medicine. Published September 23, 2026. Opened 2026-10-07.
  8. U.S. Food and Drug Administration. Warning letter, MARCS-CMS 720213, March 6, 2026. Opened 2026-10-07.

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.