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Short answer: Reishi (Ganoderma lucidum), also called lingzhi, has a long history in East Asian traditional medicine. Its main compounds, polysaccharides such as beta-glucans and triterpenes, are studied for effects on the immune system, mostly in labs and animals. Human evidence is limited: a Cochrane review found that reishi did not improve blood sugar, cholesterol or blood pressure in people with type 2 diabetes, and the FDA has not approved it for any condition. Side effects can include nausea, insomnia and dry mouth, and powdered reishi has been linked to rare but serious liver injury. Check with your provider if you take blood thinners or immunosuppressants.
Reishi is one of the most widely used medicinal mushrooms, and it shows up in teas, capsules and mushroom coffee blends. Here is what reishi is, what the research does and does not show, its side effects including the liver reports, drug interactions and how to choose a product.
What you'll learn
- What reishi mushroom is and what is in it
- What the research shows, and what it does not
- Side effects, including liver injury reports
- Drug interactions and who should avoid reishi
What is reishi mushroom?
Reishi is a mushroom that grows on live trees. Scientists call it Ganoderma lucidum or Ganoderma sinense; in traditional Chinese medicine it is known as Ling Zhi, and in Japan as reishi. There are many other Ganoderma mushrooms, and it is hard to tell the medicinal types apart from the others (National Cancer Institute). Reishi has been used for a very long time in East Asia, where it was thought to prolong life, prevent aging and increase energy (National Cancer Institute).
What is in reishi?
The compounds researchers study are beta-glucan polysaccharides and triterpenes (Memorial Sloan Kettering). Reishi is usually dried and taken as a liquid extract, capsule or powder (National Cancer Institute), and it is traditionally prepared by boiling (Wanmuang et al., 2007).
Reishi benefits: what the research shows
| Area | What studies found | How strong is the evidence? |
|---|---|---|
| Immune system | Reishi extracts showed immune-modulating effects in lab and animal studies (Memorial Sloan Kettering). Small human studies in China and Japan have looked at immune measures, mostly in people with cancer (National Cancer Institute). | Mostly lab and animal work; human studies are small. |
| Antioxidants | In 10 healthy volunteers, a single dose raised the blood's antioxidant capacity for a few hours, with no harmful effects seen in short-term use (Wachtel-Galor et al., 2004). | One small, short study; the authors said longer studies are needed. |
| Blood sugar, cholesterol and blood pressure | A Cochrane review of 5 trials with 398 participants found that 1.4 to 3 g a day for 12 to 16 weeks did not significantly improve HbA1c, fasting glucose, cholesterol or blood pressure in people with type 2 diabetes (Klupp et al., 2015). | Evidence does not support reishi for these risk factors. |
| Other uses | A few small clinical studies have looked at other outcomes (Memorial Sloan Kettering). | Too limited to draw conclusions. |
Overall, reishi is widely used and widely studied in the lab, but good human evidence is thin. The FDA has not approved reishi as a treatment for cancer or any other medical condition (National Cancer Institute).
Reishi side effects
Reported side effects include nausea, insomnia, dry mouth, constipation, itching and dizziness (Memorial Sloan Kettering). In the Cochrane review, people taking reishi for four months were somewhat more likely than those taking placebo to report a side effect, though none were serious (Klupp et al., 2015).
Reishi and liver toxicity
Liver injury from reishi is rare but has been reported. Memorial Sloan Kettering lists case reports of liver toxicity with powdered reishi, including one death (Memorial Sloan Kettering). The first case was described in Hong Kong in 2004 (Yuen et al., 2004), and a fatal case of sudden, severe hepatitis followed in Thailand (Wanmuang et al., 2007). In both, the patients had previously drunk traditionally boiled reishi without problems; the liver injury appeared 1 to 2 months after they switched to reishi powder, and both were also taking other remedies (Wanmuang et al., 2007).
Case reports cannot prove that reishi alone caused the injury, but they are a reason for caution. Stop taking reishi and contact a provider if you notice signs of liver problems, such as yellowing of the skin or eyes, and ask your provider before using it if you have liver disease.
Drug interactions
According to Memorial Sloan Kettering (Memorial Sloan Kettering):
| Taking | Possible concern |
|---|---|
| Blood thinners or antiplatelet drugs (such as warfarin) | Reishi can increase the risk of bleeding and may change clotting test results |
| Immunosuppressants | Reishi can enhance the immune response |
| Chemotherapy | In theory, reishi may interact with some cancer drugs |
| Medicines processed by liver enzymes CYP2E1, CYP1A2 or CYP3A | Reishi blocked these enzymes in lab studies; the clinical importance is unknown |
Reishi spore powder has also been found to raise the blood level of CA72-4, a tumor marker, which could confuse test results for people being monitored for cancer (Memorial Sloan Kettering).
Who should avoid reishi or ask first
- People taking blood thinners, antiplatelet drugs or immunosuppressants (Memorial Sloan Kettering).
- Anyone being treated for or monitored for cancer (Memorial Sloan Kettering).
- People with liver disease, given the liver injury reports (Wanmuang et al., 2007).
- People who are pregnant or breastfeeding, or who are having surgery; ask your provider first.
Reishi tea, powder and mushroom coffee
Reishi is sold as tea, powdered extracts, capsules and as an ingredient in mushroom coffee blends. The FDA does not regularly review how supplements are made, so batches and brands may not be the same (National Cancer Institute). Look for the species name (Ganoderma lucidum), the part used and the amount per serving. For more, see how to choose high-quality mushroom extracts, mushroom coffee: benefits, ingredients and research and mushroom coffee side effects.
Common myths (quick reality check)
Myth: Reishi is proven to boost immunity. Reality: Most immune research is in labs and animals; human studies are small and mostly in people with cancer.
Myth: Reishi lowers blood sugar and cholesterol. Reality: A Cochrane review found no significant improvement in blood sugar, cholesterol or blood pressure in people with type 2 diabetes.
Myth: Reishi is natural, so it is completely safe. Reality: Side effects are usually mild, but powdered reishi has been linked to rare serious liver injury, and it can interact with blood thinners.
Frequently asked questions (FAQ)
What are the benefits of reishi mushroom?
Reishi is studied mainly for effects on the immune system, mostly in labs and animals. Human evidence is limited, and reviews have not found clear benefits for blood sugar or cholesterol.
What is reishi mushroom good for?
It has a long history in traditional medicine for energy and longevity, but the FDA has not approved it for any condition and good human evidence is thin.
What are the side effects of reishi?
Reported side effects include nausea, insomnia, dry mouth, constipation, itching and dizziness. Rarely, powdered reishi has been linked to liver injury.
Can reishi damage your liver?
Rarely. Case reports describe liver injury with reishi powder, including one death. Ask your provider before use if you have liver disease.
Who should not take reishi?
People on blood thinners, antiplatelet drugs or immunosuppressants, those being treated for cancer, and people with liver disease should avoid it or check with a provider first.
Is reishi tea safe?
Traditionally boiled reishi has a long history of use, and in the liver case reports problems appeared after switching to powder. Talk to your provider if you take medication.
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Disclaimer and when to seek help
This article is for general education and is not medical advice. These statements have not been evaluated by the Food and Drug Administration. Our products are not intended to diagnose, treat, cure, or prevent any disease. Talk to your health care provider before using reishi, especially if you take blood thinners, immunosuppressants or other medication, have liver disease, are being treated for cancer, are pregnant or breastfeeding, or are having surgery.
References
- National Cancer Institute, PDQ Integrative, Alternative, and Complementary Therapies Editorial Board. "Medicinal Mushrooms (PDQ)-Patient Version". Updated July 11, 2024.
- Memorial Sloan Kettering Cancer Center. "Reishi Mushroom" About Herbs, Botanicals and Other Products. Last updated May 5, 2026.
- Klupp NL, et al. "Ganoderma lucidum mushroom for the treatment of cardiovascular risk factors." Cochrane Database of Systematic Reviews, 2015;(2):CD007259. doi:10.1002/14651858.CD007259.pub2
- Wachtel-Galor S, et al. "Ganoderma lucidum ('Lingzhi'); acute and short-term biomarker response to supplementation." International Journal of Food Sciences and Nutrition, 2004;55(1):75-83. doi:10.1080/09637480310001642510
- Wanmuang H, et al. "Fatal fulminant hepatitis associated with Ganoderma lucidum (Lingzhi) mushroom powder." Journal of the Medical Association of Thailand, 2007;90(1):179-181. PubMed 17621752
- Yuen MF, et al. "Hepatotoxicity due to a formulation of Ganoderma lucidum (lingzhi)." Journal of Hepatology, 2004;41(4):686-687. doi:10.1016/j.jhep.2004.06.016
