Turkey Tail Safety and Side Effects
What the sources report about turkey tail (Trametes versicolor) side effects, tolerability in trials, pregnancy, medicines and product quality, and what has not been studied.
Content last updated . This page has not been medically reviewed.
Safety first. Supplements can cause side effects and interact with medicines. Read mushroom safety and interactions before you use any mushroom product.
Quick answer
In the studies and monographs we read, turkey tail (Trametes versicolor, also called Coriolus versicolor) and its extract PSK are described as generally well tolerated, with few and mostly mild side effects. That is a statement about the products studied, mainly a prescription-type extract in Japan and a few small trials. It is not proof that every turkey tail capsule, powder or tea is safe, and for several safety questions we did not find a source. Where that is the case this page says so.
Reported side effects
| Question | What the source found | Strength of evidence |
|---|---|---|
| Common or rare side effects | A cancer-center monograph lists dark-colored stool and darkening of fingernails as possible side effects. [1] | Case-level reports; rare |
| Stomach and blood effects | Low-grade blood and gastrointestinal effects were reported when used with chemotherapy; the monograph notes these may come from the chemotherapy itself. [2] | Mixed; cannot be assigned to turkey tail |
| PSK in patients in Japan | The U.S. National Cancer Institute (NCI) says few adverse events have been reported with PSK. [3] | Promising but limited (extract, not supplements) |
| Tolerability in a small trial | In a phase 1 trial in 9 women with breast cancer who completed 6 weeks of 3, 6 or 9 grams a day of a turkey tail preparation, there were nine adverse events (7 mild, 1 moderate, 1 severe). [4] | Promising but limited (very small) |
| Side effects of chemotherapy in colorectal cancer | A Cochrane review is uncertain whether the extract changes chemotherapy side effects; it found very low-certainty evidence. [5] | Insufficient evidence |
The numbers above are amounts used in a trial, not recommendations. A clinician or pharmacist decides what is right for a person.
Who should be especially careful
- Pregnancy and breastfeeding: the monograph says pregnant or breastfeeding women should avoid Coriolus until safety data become available. [6] See pregnancy and breastfeeding.
- People having cancer treatment: tell the oncology team about any turkey tail product. The monograph notes that effects may overlap with chemotherapy side effects, which makes problems harder to sort out. [2] See turkey tail, PSK and cancer care.
- People with autoimmune conditions or transplants: the monograph says studies suggest turkey tail has immunostimulant properties. [7] We did not read a source that tests it in these groups, so we cannot say it is safe. Ask the specialist; see mushrooms, autoimmune conditions and transplants.
- Children, older adults, liver and kidney disease, surgery: not described in the sources we read for turkey tail. That is not proof of safety.
- Allergy: we did not read a source describing turkey tail allergy. Mushroom allergy in general is covered at mushroom allergy and food intolerance.
Medicines
Proper evidence not found for documented turkey tail interactions: the NCI summary does not address drug interactions for any product it covers, [8] and we did not find an interaction listed in the cancer-center monograph we read. This is not proof of safety. The monograph states that herbal supplements can interact with some medications and affect how they work. [9] Ask a pharmacist, and see how interactions work and mushroom supplement and medicine interactions.Product quality and labels
NCI states that supplements may differ from lot to lot and that labeled ingredients are not guaranteed. [10] The monograph adds that many over-the-counter products are not standardized, so potency is hard to compare. [11] Product type matters: a purified extract (PSK or PSP) is not the same as ground mushroom or mycelium grown on grain. See fruiting body versus mycelium and quality testing and certifications.Regulators
- Japan: PSK is an approved cancer-treatment product, per NCI. [12]
- United States: NCI says the FDA has not approved medicinal mushrooms as a treatment for cancer or any other medical condition. [13]
What we could not find
We did not read a source on turkey tail and liver or kidney disease, long-term use in healthy people, or use in children. Proper evidence not found (searched the NCI summary, the cancer-center monograph and PubMed for turkey tail and Trametes versicolor safety).Frequently asked questions
What are the side effects of turkey tail?
Possible dark stool and darkening of fingernails, according to a cancer-center monograph. [1] Few adverse events have been reported with PSK. [3]
Is turkey tail safe in pregnancy?
Not established. The monograph advises avoiding it while pregnant or breastfeeding until safety data exist. [6]
Does turkey tail interact with medicines?
We did not read a documented interaction, and the main summaries do not address interactions. [8] That is not proof of safety; ask a pharmacist.
Is turkey tail safe with chemotherapy?
Trials of PSK with chemotherapy in Japan reported few adverse events, [3] but the Cochrane review could not tell whether the extract changes chemotherapy side effects. [5] Ask the oncology team before using any product.
Can turkey tail cause liver problems?
Proper evidence not found. We did not read a report of liver injury linked to turkey tail. Liver warning signs for any supplement are on liver safety and supplements.
References
- Memorial Sloan Kettering Cancer Center, Coriolus versicolor (About Herbs). Read 2026-10-23.
- Memorial Sloan Kettering Cancer Center, Coriolus versicolor (About Herbs). Read 2026-10-23.
- National Cancer Institute (NCI), PDQ Integrative, Alternative, and Complementary Therapies Editorial Board, Medicinal Mushrooms (PDQ), Health Professional Version, updated November 6, 2024. Read 2026-10-23.
- Torkelson CJ, et al. Phase 1 clinical trial of Trametes versicolor in women with breast cancer. ISRN Oncology, 2012. Read 2026-10-23.
- Coriolus (Trametes) versicolor mushroom to reduce adverse effects from chemotherapy or radiotherapy in people with colorectal cancer. Cochrane Database of Systematic Reviews, 2022. Read 2026-10-23.
- Memorial Sloan Kettering Cancer Center, Coriolus versicolor (About Herbs). Read 2026-10-23.
- Memorial Sloan Kettering Cancer Center, Coriolus versicolor (About Herbs). Read 2026-10-23.
- National Cancer Institute (NCI), PDQ Integrative, Alternative, and Complementary Therapies Editorial Board, Medicinal Mushrooms (PDQ), Health Professional Version, updated November 6, 2024. Read 2026-10-23.
- Memorial Sloan Kettering Cancer Center, Coriolus versicolor (About Herbs). Read 2026-10-23.
- National Cancer Institute (NCI), PDQ Integrative, Alternative, and Complementary Therapies Editorial Board, Medicinal Mushrooms (PDQ), Health Professional Version, updated November 6, 2024. Read 2026-10-23.
- Memorial Sloan Kettering Cancer Center, Coriolus versicolor (About Herbs). Read 2026-10-23.
- National Cancer Institute (NCI), PDQ Integrative, Alternative, and Complementary Therapies Editorial Board, Medicinal Mushrooms (PDQ), Health Professional Version, updated November 6, 2024. Read 2026-10-23.
- National Cancer Institute (NCI), PDQ Integrative, Alternative, and Complementary Therapies Editorial Board, Medicinal Mushrooms (PDQ), Health Professional Version, updated November 6, 2024. Read 2026-10-23.
Education, not medical advice. This page is for general information. It does not diagnose or treat any condition and is not a substitute for care from a qualified health professional. Natural does not automatically mean safe. Ask a clinician or pharmacist before changing your care, especially if you take medication, are pregnant or breastfeeding, or have a health condition.