Reishi as an "Adaptogen": Claim Check
Reishi is often sold as a calming adaptogen for stress and sleep. This claim check separates traditional use from research, and lists documented cautions.
Content last updated . This page has not been medically reviewed.
Safety first. Natural products can cause side effects and interact with medicines. Read who should be careful, by situation before you use anything on this page.
The claim as marketed: "Reishi is an adaptogen. It calms stress, helps you sleep, balances cortisol and works like ashwagandha." This page checks each part against the sources we read. The full reishi profile is in the Mushrooms library: Reishi (Ganoderma lucidum).
Read this first: documented cautions. Memorial Sloan Kettering Cancer Center (MSK) lists liver injury and insomnia among reishi's possible side effects. [1] It also says reishi can increase bleeding risk, so people on blood thinners such as warfarin should talk to their provider, and that people on immunosuppressants should too. [1] Liver warning signs are described on liver safety and supplements; contact a clinician if you are worried. For poisoning concerns in the US, Poison Help is 1-800-222-1222.
What reishi is, and a naming trap
MSK gives the scientific name as Ganoderma lucidum, a fungus. [1] GBIF accepts Ganoderma lucidum, and lists Ganoderma lingzhi as a synonym of Ganoderma sichuanense. [2] Some papers use "lingzhi" for the species they studied, so a result for one named species may not carry to a product labeled with another. A 2023 case report, for example, describes Ganoderma lingzhi powder. [3]Traditional use (not proof)
MSK describes reishi as holding an important place in the traditional medical systems of China, Japan, Korea and other Asian countries. [1] A 2023 review says G. lucidum is traditionally used for liver disorders, high blood pressure, insomnia, diabetes and cancer. [4] These are descriptions of traditions, not findings. See reishi and cordyceps in Chinese medicine.What research shows, claim by claim
| Claim | What the sources we read found | Strength of evidence |
|---|---|---|
| "Calms stress and anxiety" | MSK's clinical summary says clinical studies indicate benefit in lowering anxiety. [1] We did not read the underlying trial. | Promising but limited |
| "Helps you sleep" | Proper evidence not found. We searched PubMed for Ganoderma with insomnia or sleep and found mouse and laboratory studies; in one, mice given certain reishi formulations for 14 days had shorter sleep latency. [5] MSK lists insomnia as a possible side effect. [1] | Preclinical (animals) for sleep |
| "Fights fatigue" | MSK reports subjective improvements in fatigue in one cited study, and does not describe a controlled trial for it. [1] MSK also says reishi did not influence blood or body measurements in patients with fibromyalgia. [1] A separate trial gave women with fibromyalgia 6 g a day for 6 weeks and found better results on some fitness tests. [6] | Limited, mixed |
| "Balances cortisol" | Proper evidence not found. We did not locate a human trial of reishi measuring cortisol among the sources we read. | No good evidence read |
| "Supports the immune system" | MSK describes immune-related effects mostly from laboratory work and small clinical studies, in people with cancer. [1] See reishi and the immune system. | Preclinical and limited |
| "Works like ashwagandha" | Proper evidence not found. We searched PubMed for Ganoderma together with ashwagandha or Withania and found no head-to-head trial. The two are different organisms with different evidence. See ashwagandha. | No comparison exists in sources read |
A 2025 meta-analysis pooled 17 randomized trials (971 people, amounts from 200 to 11,200 mg a day, 1 to 24 weeks). It found small changes in body mass index, creatinine, an antioxidant enzyme and heart rate, and none in blood pressure, blood sugar, cholesterol or liver enzymes. The authors graded the certainty of evidence as very low across all outcomes. [7] The abstract we read did not report stress or sleep outcomes.
Why the form matters
Spore powder, fruiting body, extract and mycelium-on-grain are different products, and a result for one should not be assumed for another. See reishi species, spores and fruiting body products.Frequently asked questions
Is reishi an adaptogen?
"Adaptogen" is a contested label, not a regulatory category; the EU herbal committee said in 2008 the term is not accepted in EU pharmacological and clinical language. [8] Reishi is described in traditional systems, and some sellers apply the word to it.
Does reishi help with sleep?
Proper evidence not found in human trials we searched. Mouse studies exist, and MSK lists insomnia as a reported side effect. [5][1]
Does reishi lower cortisol?
We did not find a human trial of reishi and cortisol in the sources we read, so no claim can be made. Cortisol is also only a marker, not a measure of feeling better.
Can reishi harm the liver?
Case reports exist, including one death with powdered reishi according to MSK. [1] A 2023 case report involved reishi powder together with alcohol. [3] Ask a clinician if you have liver disease.
Who should avoid reishi?
The sources we read name people on blood thinners or immunosuppressants as needing medical advice first. [1] A pharmacist or clinician can check your own medicines.
More details: evidence, limits and cautions
The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.
Safety: who should ask first
- Liver. MSK lists case reports of liver damage with powdered reishi, one leading to death. [1] A 2023 case report describes acute hepatitis in a 47-year-old man who took reishi powder and alcohol; labs returned to normal at two weeks. [3]
- Medicines. MSK flags anticoagulants and antiplatelets (bleeding), immunosuppressants, and notes that reishi extracts may prolong blood-clotting tests. [1] In test-tube work reishi polysaccharides inhibited some liver enzymes; MSK says the clinical relevance is not known. [1] See medicine interactions.
- Cancer follow-up tests. MSK says reishi spore powder may raise a tumor marker called CA72-4, which could show up on test results. [1] A 2023 review also raised this concern for high amounts of spore extract. [4]
- Autoimmune conditions. MSK says reishi may trigger or worsen autoimmune skin disease, though causation is not settled. [1]
- Children. MSK describes one case of acute neurotoxicity in a 9-year-old after several medicinal fungi supplements that included reishi. [1]
- Pregnancy, breastfeeding, surgery. The sources we read do not address these for reishi. That is not evidence of safety; see pregnancy and breastfeeding and supplements before surgery.
- Quality. See independent testing for adaptogens.
References
- Memorial Sloan Kettering Cancer Center. Reishi Mushroom. Integrative Medicine herbs database, page updated May 5, 2026. Read 2026-10-23.
- GBIF Secretariat. GBIF Backbone Taxonomy species match, queried through api.gbif.org on 2026-10-23. Read 2026-10-23.
- Guedikian A, Kim J, Singh A. Ganoderma lingzhi (reishi mushroom)-induced acute liver injury in the setting of alcohol use: a case report and review of the literature. Cureus. 2023. PubMed 37885515. Read 2026-10-23.
- Thuy NTT, Tu LTC, Thu NTM, et al. Pharmacological activities and safety of Ganoderma lucidum spores: a systematic review. Cureus. 2023. PubMed 37790044. Read 2026-10-23.
- Li Y, Liu Y, Wu J, et al. The anti-fatigue and sleep-aiding effects vary significantly among different recipes containing Ganoderma lucidum extracts. Heliyon. 2024 (mouse study). PubMed 38770283. Read 2026-10-23.
- Collado Mateo D, Pazzi F, Dominguez Munoz FJ, et al. Ganoderma lucidum improves physical fitness in women with fibromyalgia. Nutr Hosp. 2015. PubMed 26545669. Read 2026-10-23.
- Jafari A, Mardani M, Mirzaei Fashtali A, et al. The nutritional significance of Ganoderma lucidum on human health: a GRADE-assessed systematic review and meta-analysis of clinical trials. Food Sci Nutr. 2025. PubMed 40510787. Read 2026-10-23.
- European Medicines Agency, Committee on Herbal Medicinal Products (HMPC). Reflection paper on the adaptogenic concept. EMEA/HMPC/102655/2007, adopted 8 May 2008. Read 2026-10-23.