How Do You Feel After Taking Reishi? Side Effects and Safety

Most people feel nothing in particular after taking reishi: it tastes bitter, and the placebo-controlled trials, at 1.4 to 3 g a day for up to 16 weeks and 4 g of extract a day for ten days, recorded no more adverse events on reishi than on placebo and normal liver and kidney blood tests.^{1, 2, 4} The serious reports are rare and specific: three published cases of liver injury, one fatal, all with reishi powder, one with alcohol, and one of eosinophilia with liver nodules.^{5, 6, 7, 14} The clotting and blood-sugar studies were reassuring, but anyone on anticoagulants, diabetes medicines, immune-suppressing medicines or cancer treatment still tells their pharmacist or clinic first.^{8, 10} Pregnancy, breastfeeding and children: no data, so not recommended. Reishi safety page of do mushroom supplements work?; the benefit trials are in what reishi is good for.

Sources checked on 29 October 2026.

How do you feel after taking reishi?

Bitter, first: reishi's triterpenes are why it is usually sold in capsules. Sixteen healthy volunteers took 2 g of reishi extract twice a day for ten days with no adverse effects and normal blood chemistry.¹ Eighteen healthy adults took 1.44 g a day for four weeks and their liver and kidney markers did not move.² Sixty-four women with fibromyalgia took 6 g a day for six weeks against carob flour; the report gives fitness results and no side-effect data.³ None of these groups reported feeling calmer, sleepier or more energetic as a measured outcome, so the "deep calm" and "best sleep ever" accounts online are reports, not results.

What are the side effects of reishi?

The trial list is short, whether reishi is taken as a tea, powder, capsule or tincture: at 1.4 to 3 g a day for 10 days to 16 weeks, adverse events were no more frequent than on placebo and no serious event was attributed to reishi; the 6 g fibromyalgia trial did not report side effects.^{1, 2, 3, 4} The traditional list, dry mouth and throat, itching, rash, stomach upset, nosebleed and dizziness, went uncaught by the trials, so each is uncommon if real. Mushroom allergy exists; the signs and what to do are below. For other species, what are the side effects of mushroom supplements? carries the full interaction table.

Can reishi affect the liver?

Yes, rarely, and the published cases share a form. The first report, from Hong Kong in 2004, described liver injury in a patient taking a reishi powder formulation.⁵ The second, from Thailand in 2007, described fatal fulminant hepatitis after one to two months of reishi powder in a patient also taking other medicines; both reports note that the patients had previously taken boiled reishi without harm.⁶ The third, from 2023, was a 47-year-old man who developed acute hepatitis after reishi powder taken alongside alcohol; it resolved within two weeks of stopping.⁷ A 2021 Japanese report describes a 61-year-old man on a reishi product whose eosinophils rose markedly, with a slight liver-enzyme rise and several liver nodules, all gone after he stopped.¹⁴ Against those cases sit the trials, in which 1.44 g a day of encapsulated powder for four weeks and 4 g of extract a day for ten days left liver tests normal, so the powder form alone does not explain them.^{1, 2} Rare as that is, it is why reishi is not for anyone with liver disease, heavy alcohol use or a medicine with its own liver warning. The warning signs: dark urine, pale stools, yellowing of the skin or eyes, itching, nausea with pain under the right ribs, or unusual tiredness; see a GP the same day.¹² "Is reishi good for fatty liver?" has no human trial behind it: the only human liver data are these cases and the trials' normal blood tests.

Does reishi interact with blood thinners or diabetes medicines?

Two interactions have been studied in people; the rest have not. Clotting: an older Chinese report described reishi inhibiting platelet clumping, the origin of "reishi thins the blood".⁹ When 40 healthy volunteers took 1.5 g of reishi a day or placebo for four weeks, no clotting or platelet measure changed, and the anaesthetists who ran it judged reishi unlikely to raise surgical bleeding in healthy people.⁸ Blood sugar: 1.4 to 3 g a day for 12 to 16 weeks did not change HbA1c or fasting glucose in the Cochrane review of 398 people with type 2 diabetes or cardiovascular risk factors, so it did not add to the glucose-lowering of diabetes medicines in the people studied.^{4, 10} Everything else is unstudied; for immune-suppressing medicines the caution is mechanistic: a review of 34 trials of fungal beta-glucans found immune-marker changes that were inconsistent between studies.¹¹

Can you take reishi every day?

Daily reishi at 1.4 to 3 g for 12 to 16 weeks produced no excess of adverse events in adults with type 2 diabetes and in healthy volunteers for four weeks or less; the Cochrane review counted adverse events 1.67 times as often on reishi over four months (95% CI 0.86 to 3.24, not distinguishable from placebo), none serious.^{1, 2, 4, 10} Beyond 16 weeks there is no trial. A reasonable pattern is the one the trials used: a label dose, daily, judged at eight to sixteen weeks.

Who should not take reishi?

Pregnant and breastfeeding women and children, because no trial has included them. Anyone with a mushroom allergy. Anyone with liver disease, a past drug-induced liver injury or heavy alcohol use, because of the three case reports. Anyone with a bleeding disorder, a low platelet count or a planned operation, as a precaution. Anyone on immune-suppressing medicines, biologics, chemotherapy, immunotherapy or hormone therapy for cancer, until their specialist has said yes. Low blood pressure appears on most lists as a precaution; no human trial has measured it, so it is caution, not evidence.

What should you do if you feel unwell after taking reishi?

Stop taking it, keep the packaging, and match the symptom to the route. A rash, itching, swelling or wheeze is an allergy until proven otherwise: a pharmacist for a mild rash, 999 for swelling of the face or throat or difficulty breathing. The liver signs above are a same-day GP appointment or NHS 111; say you have been taking reishi.^{5, 6, 7} Unusual bruising or bleeding on an anticoagulant is a call to the clinic. Then report it to your local authority's trading standards or environmental health team, which works with the Food Standards Agency.¹³

What we don't know

No trial has followed daily reishi beyond 16 weeks; year-round use is untested.^{4, 10} No study has measured sleep, drowsiness or alertness as an outcome in healthy adults. The liver reports are four published cases with no denominator, so how often reishi powder injures the liver is unknown.^{5, 6, 7, 14} Apart from the clotting and glucose measures above, no interaction with any medicine has been studied in people.

Frequently asked questions

Is it safe to take reishi every day?

In the trials, yes, for up to 16 weeks at 1.4 to 3 g a day, in adults without liver disease and not on the medicines above; longer is untested.^{4, 10}

What are the downsides and risks of reishi?

A bitter taste, uncommon reports of dry mouth, stomach upset or dizziness, three published liver-injury cases with reishi powder and one of eosinophilia with liver nodules, and no trial beyond 16 weeks.^{5, 6, 7, 14}

Who cannot take reishi?

Pregnant and breastfeeding women and children (no data), anyone with a mushroom allergy or liver disease, and anyone on the medicines in the table without their clinic's agreement.

Does reishi make you sleepy?

No trial has recorded drowsiness or measured sleep, sleepiness or alertness in otherwise healthy adults.^{1, 2, 3, 4} The sleep reputation rests on rat studies of sleep time;¹⁵ what reishi is good for explains why no human sleep trial exists. If reishi leaves you drowsy, take it in the evening or stop; drowsiness that persists is a GP matter.

Sources

1. Wicks SM, et al. Safety and tolerability of Ganoderma lucidum in healthy subjects. Randomised placebo-controlled trial, 16 adults, 10 days; funding not stated. American Journal of Chinese Medicine, 2007. PubMed 17597499.
2. Wachtel-Galor S, et al. Ganoderma lucidum ("Lingzhi"): biomarker responses in a controlled human supplementation study. Placebo-controlled crossover trial, 18 adults, 4 weeks; non-commercial funding. British Journal of Nutrition, 2004. PubMed 14756912.
3. Collado Mateo D, et al. Ganoderma lucidum improves physical fitness in women with fibromyalgia. Randomised trial against carob, 64 women, 6 weeks; non-commercial funding. Nutrición Hospitalaria, 2015. PubMed 26545669.
4. Klupp NL, et al. Ganoderma lucidum for cardiovascular risk factors of metabolic syndrome. Randomised placebo-controlled trial, 84 adults, 16 weeks; investigator-led, part-funded by the supplement's supplier. Scientific Reports, 2016. PubMed 27511742.
5. Yuen MF, et al. Hepatotoxicity due to a formulation of Ganoderma lucidum (lingzhi). Case report, 1 patient. Journal of Hepatology, 2004. PubMed 15464254.
6. Wanmuang H, et al. Fatal fulminant hepatitis associated with Ganoderma lucidum mushroom powder. Case report, 1 patient. Journal of the Medical Association of Thailand, 2007. PubMed 17621752.
7. Guedikian R, et al. Reishi-induced acute liver injury in the setting of alcohol use. Case report, 1 patient. Cureus, 2023. PubMed 37885515.
8. Kwok Y, et al. Platelet and global haemostatic effects of Ganoderma lucidum in healthy volunteers. Randomised placebo-controlled trial, 40 adults, 4 weeks; non-commercial funding. Anesthesia & Analgesia, 2005. PubMed 16037156.
9. Tao J, Feng KY. Inhibitory effect of Ganoderma lucidum on platelet aggregation. Laboratory and uncontrolled study, 15 volunteers and 33 patients. Journal of Tongji Medical University, 1990. PubMed 2098581.
10. Klupp NL, et al. Ganoderma lucidum mushroom for the treatment of cardiovascular risk factors. Cochrane review, 5 trials, 398 adults; non-commercial funding. Cochrane Database of Systematic Reviews, 2015. PubMed 25686270.
11. Vlassopoulou M, et al. Effects of fungal beta-glucans on health. Systematic review, 34 randomised trials; funding not stated. Food & Function, 2021. PubMed 33876798.
12. NHS. Jaundice. Page last reviewed 22 January 2024. nhs.uk.
13. Food Standards Agency. How to report a food safety or hygiene issue for members of the public. gov.uk.
14. Kogure T, et al. Hypereosinophilia with hepatic nodule formation caused by Ganoderma lucidum. Case report, 1 patient. Internal Medicine, 2021. PubMed 34911873.
15. Cui XY, et al. Extract of Ganoderma lucidum prolongs sleep time in rats. Animal study. Journal of Ethnopharmacology, 2012. PubMed 22207209.

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