Cordyceps Side Effects and Medicine Cautions
Documented and theoretical cordyceps cautions: blood sugar and blood thinner medicines, bleeding, hormone-sensitive and blood cancers, contamination and children, with what is not known.
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.
Read this first. Memorial Sloan Kettering Cancer Center (MSK) advises talking with your healthcare provider if you take insulin or another medicine that lowers blood sugar, because cordyceps can also lower blood sugar and may cause harm. It gives the same advice for blood thinners such as warfarin, because cordyceps may increase the risk of bleeding. [1] Tell your surgical or dental team about any cordyceps product. A pharmacist or prescriber decides what is safe for you; do not change a prescribed medicine on your own.
What "cordyceps" means here
Most cautions below come from reviews of Ophiocordyceps sinensis (the wild caterpillar fungus, formerly Cordyceps sinensis) and from trials of products with that older name. [2] Cordyceps militaris is a different species. [3] Whether a caution transfers from one to the other is not established in the sources we read. See the species question.Documented, reported and theoretical
| Concern | What the source says | How firm it is |
|---|---|---|
| Common side effects | MSK states that no major side effects have been reported. [1] | Absence of reports is not proof of safety |
| Blood sugar medicines | Laboratory studies suggest additive blood-sugar-lowering effects; clinical relevance has not been determined. [1] | Theoretical (laboratory) |
| Blood thinners and antiplatelet medicines | Laboratory studies suggest cordyceps inhibits platelet aggregation and may add to these drugs. [1] | Theoretical (laboratory) |
| Bleeding | A case report links excessive bleeding after a tooth extraction with daily cordyceps use as a tonic. [1] | Single case report |
| Blood-forming cancers | Animal studies showed growth of red blood cell precursors, so MSK says it should not be used by people with myelogenous types of cancer. [1] | Animal findings |
| Prostate and hormone-sensitive cancers | In mice, C. sinensis raised testosterone and prostate weight and made one androgen-responsive cell line grow faster; the authors said more study is needed on whether it is safe for people with prostate cancer. [4] MSK also reports raised testosterone in mice. [1] | Preclinical (animals and cells) |
| Immune-modulating medicines | Laboratory studies show cordyceps raises activity of some immune cells. [1] A Cochrane review of five small trials in kidney transplant recipients compared it with azathioprine or combined it with a lower dose of cyclosporin, and judged all of them to have unclear risk of bias. [5] | Unclear; talk to the transplant team first |
For why some interactions are documented and others only theoretical, see how interactions work and mushroom supplements and medicine interactions.
Autoimmune conditions and transplants
Proper evidence not found for the safety of cordyceps in autoimmune disease. We looked at MSK, a Cochrane review of kidney transplants and PubMed results for cordyceps and adverse effects, and none addressed autoimmune conditions. Because lab studies show immune-cell stimulation, ask your specialist before using any product; see mushrooms, autoimmune conditions and transplant medicines.Contamination
- A 1996 report describes two people with lead poisoning from contaminated cordyceps powder. [6]
- A 2018 study of wild O. sinensis found total arsenic of 4.00 to 5.25 mg/kg, mostly unidentified organic forms. [7]
These findings show that source and testing matter, not that every product is contaminated. See quality testing for supplements.
Children, pregnancy and breastfeeding
A 2026 case report described a 9-year-old with cerebral palsy and epilepsy who developed seizures, hallucinations and altered mental status after taking several medicinal fungus supplements, including Ganoderma lucidum and Cordyceps sinensis, with improvement after stopping. The authors suggested a supplement-related cause but could not separate the ingredients. [8] Pregnancy and breastfeeding are not described in the sources we read. See children and teens and pregnancy and breastfeeding.Liver and kidney
Liver safety is not described in the sources we read for cordyceps. In a Cochrane review of five small trials in kidney transplant recipients, the authors said results should be interpreted with caution and longer studies are needed. [5] See liver safety.About amounts
We do not give amounts to take. Trials used products labeled with the older name at amounts such as 333 mg three times a day for 12 weeks, which describes a trial only. [9]Reporting a problem
If you have a reaction, stop the product and contact a clinician. For serious symptoms such as heavy bleeding, seizure or collapse, call 911. See side effects and reporting.Frequently asked questions
Does cordyceps have side effects?
MSK says no major side effects have been reported, but it also describes a bleeding case report and medicine cautions. [1]
Can I take cordyceps with warfarin?
MSK advises talking with your healthcare provider first because cordyceps may increase bleeding risk. Ask your prescriber or pharmacist. [1]
Does cordyceps affect blood sugar?
MSK says it can lower blood sugar and may cause harm if you take insulin or another blood sugar medicine. [1]
Is cordyceps safe with cancer?
Not for everyone. MSK says it should not be used by people with myelogenous cancers, and a mouse study raised a question for prostate cancer. Tell the oncology team about every supplement. [1][4]
Is cordyceps safe for children?
Not established in the sources we read. A case report describes seizures in a child taking a multi-fungus supplement. [8]
References
- Memorial Sloan Kettering Cancer Center, Cordyceps, About Herbs, Botanicals & Other Products (last updated 2022-02-10). Read 2026-10-23.
- Global Biodiversity Information Facility (GBIF), species match for Cordyceps sinensis (listed as a synonym of Ophiocordyceps sinensis, accepted key 2560562), usage key 2560564. GBIF species page. Read 2026-10-23 through the GBIF species-match service.
- Global Biodiversity Information Facility (GBIF), species match for Cordyceps militaris, usage key 7567077. GBIF species page. Read 2026-10-23 through the GBIF species-match service.
- Ma MW et al. Cordyceps sinensis promotes the growth of prostate cancer cells. Nutr Cancer 2018. Read 2026-10-23.
- Hong T, Zhang M, Fan J. Cordyceps sinensis (a traditional Chinese medicine) for kidney transplant recipients. Cochrane Database Syst Rev 2015. Read 2026-10-23.
- Wu TN et al. Lead poisoning caused by contaminated Cordyceps, a Chinese herbal medicine: two case reports. Sci Total Environ 1996. Read 2026-10-23.
- Guo LX et al. Determination of arsenic species in Ophiocordyceps sinensis from major habitats in China by HPLC-ICP-MS and the edible hazard assessment. Molecules 2018. Read 2026-10-23.
- Melek Arsoy HE, Özdemir Ö. Acute neurotoxicity in a child following multi-component medicinal fungi supplementation: a case report. BMC Complement Med Ther 2026. Read 2026-10-23.
- Chen S et al. Effect of Cs-4 (Cordyceps sinensis) on exercise performance in healthy older subjects: a double-blind, placebo-controlled trial. J Altern Complement Med 2010. Read 2026-10-23.