Last updated: October 2026
Reishi (Ganoderma lucidum) is a bitter, woody mushroom used for centuries in Chinese and Japanese tradition, mostly taken today as an evening drink. Human evidence is limited: small trials suggest less fatigue, but Cochrane reviews found no proof for heart health or cancer. Most people tolerate it well; liver injury is rare but reported.
This guide covers what reishi is, what the research shows (with an honest evidence rating), every side effect people ask about, from the liver to blood thinners, who should avoid it, how much to take and when, and the different ways to take it.
What is reishi?
Reishi, called lingzhi in Chinese, is a shiny, reddish-brown shelf fungus that grows on hardwood trees. It’s too tough and bitter to eat, so it’s taken as a tea, powder or extract. Most of its interest comes from compounds called beta-glucans and triterpenes. It isn’t psychoactive.
“Red reishi” is simply the common red form you’ll see on most labels, sold as Ganoderma lucidum or Ganoderma lingzhi. The side effects and cautions below apply whichever name is on the pack. For how it sits alongside other mushrooms, see our guides to chaga, turkey tail and lion’s mane vs reishi vs cordyceps.
Reishi benefits: what the research shows
Reishi has no authorised health claims in Great Britain, so the table below describes research only. We’ve rated each area honestly, based on how many people were studied, for how long, and whether the results have been repeated.
| Area | What the research found | Strength of evidence |
|---|---|---|
| Fatigue and wellbeing | A Chinese trial of 132 people with neurasthenia (long-term fatigue) found a reishi extract improved symptoms more than placebo after 8 weeks (Tang 2005). A pilot trial in 48 women with breast cancer reported less fatigue after 4 weeks of reishi spore powder (Zhao 2012) | Low: a few small trials |
| Stress and mood | A 30-day trial in 78 female students found better anxiety and wellbeing scores on 1,000mg a day (Mitra 2024). A 6-week pilot in women with fibromyalgia found no clear difference from placebo (Pazzi 2020) | Low: small, mixed results |
| Sleep | Mostly animal studies; we found no good human sleep trials. See reishi for sleep | Very low: animal research only |
| Immune markers | An 84-day trial in healthy adults found higher counts of some immune cells with a reishi beta-glucan (Chen 2023). A 4-week trial in 18 healthy adults found no significant change in immune or other markers (Wachtel-Galor 2004). Changes in blood markers don’t show fewer infections | Low: lab markers, not illness outcomes |
| Cholesterol and blood sugar | Cochrane review, 2015: small trials don’t support it for cardiovascular risk factors in type 2 diabetes. A 16-week trial in 84 people with type 2 diabetes found no effect on blood sugar (Klupp 2016) | Low, and mostly negative |
| Cancer | Cochrane review, 2016: not enough evidence to use it as a cancer treatment; studies were small and low quality (Jin 2016) | Insufficient |
| Skin | Interest in skincare is growing, but human evidence is limited. See reishi for skin | Very low |
In short, reishi is better described as a traditional evening ritual than a proven remedy.
Weighing it against ashwagandha? See reishi vs ashwagandha.
Reishi for sleep, stress and anxiety
These are the reasons most people in the UK search for reishi, so it’s worth being clear about what’s known.
- Sleep: reishi is traditionally taken in the evening, and many people enjoy it as part of a wind-down routine. There are no good human trials showing it improves sleep. Our reishi for sleep guide goes into the animal research, and our deep sleep guide covers the habits with the strongest evidence.
- Stress and anxiety: a couple of small trials have looked at mood and wellbeing scores, with mixed results. Reishi isn’t a treatment for anxiety. If anxiety is affecting your daily life, speak to your GP. For a ranked look at the research on other mushrooms, see the best mushrooms for anxiety, and for a herbal adaptogen with its own small trials, see holy basil.
Reishi side effects
Most people who take reishi have no problems. In a 10-day trial, 16 healthy volunteers took 2g of extract twice a day with no more side effects than placebo, and blood and urine tests stayed normal. Across the longer trials, side effects were usually mild, and there are no reliable figures for how often each one happens. In the Cochrane review of diabetes trials, people taking reishi for four months reported somewhat more side effects than those on placebo, but none were serious and the difference may have been chance.
| Side effect | Notes | What to do |
|---|---|---|
| Dry mouth, throat or nose | Listed by both the MSD Manual and Memorial Sloan Kettering | Drink water; stop if it bothers you |
| Upset stomach, nausea, diarrhoea or constipation | Nausea was among the minor side effects in the Cochrane cancer review | Take it with food or a drink; reduce the amount or stop |
| Dizziness or headache | Listed by the MSD Manual | Stop, and check your blood pressure if you take blood pressure medicine |
| Itching or skin rash | Listed by the MSD Manual and Memorial Sloan Kettering | Stop |
| Trouble sleeping | Reported in one cancer trial | Try it earlier in the evening, or stop |
| Nosebleeds or easy bruising | Listed by the MSD Manual | Stop and speak to your GP, especially if you take a blood thinner |
| Liver injury | Rare: a handful of case reports | Stop and see a GP straight away (signs below) |
Reishi and the liver
Rare but serious cases of liver injury have been reported with reishi powder. The published case reports are few:
- Hong Kong, 2004: liver toxicity in a patient taking a reishi powder formulation.
- Thailand, 2005: a fatal case of sudden, severe hepatitis. Both this patient and the Hong Kong patient had drunk traditionally boiled reishi without problems, then developed liver injury one to two months after switching to reishi powder. Both were also taking other medicines.
- USA, 2023: a 47-year-old man developed acute hepatitis after taking reishi powder alongside alcohol. He recovered fully within two weeks of stopping.
In controlled trials, tests of liver function stayed normal. A 4-week trial in healthy adults found no sign of liver or kidney harm, and an 84-day trial of a reishi beta-glucan found no significant changes in liver or kidney markers. The MSD Manual notes that reishi extract taken for up to a year might be safe, but cautions that the powdered form taken for more than a month could damage the liver.
Stop and see a GP straight away if you notice yellow skin or eyes, dark pee or itching while taking reishi. If you have liver disease or drink heavily, speak to your GP before taking it.
Medicines, surgery and who should avoid it
Blood thinners and bleeding disorders
Reishi may slow blood clotting. In an older Chinese study, people who took 1g three times a day for two weeks showed reduced platelet clumping. Memorial Sloan Kettering says reishi extracts may prolong clotting test results (INR, PT and APTT). Speak to your GP or pharmacist first if you take a blood thinner such as warfarin, heparin or clopidogrel, use anti-inflammatory painkillers such as ibuprofen or naproxen regularly, or have a bleeding disorder.
Blood pressure and diabetes medicines
Lab and animal research has suggested reishi could lower blood pressure and blood sugar. Human trials have found little effect: a 12-week trial in 26 people with borderline high blood pressure or cholesterol found no change in blood pressure, though insulin levels were lower, and a 16-week trial in people with type 2 diabetes found no change in blood sugar. Even so, if you take blood pressure or diabetes medicines, or already have low blood pressure, check with your pharmacist first and watch for dizziness.
Immunosuppressants and cancer treatment
Because reishi may stimulate parts of the immune system, it may not be safe with immunosuppressant medicines, such as those taken after an organ transplant or for some autoimmune conditions. If you’re having chemotherapy or other cancer treatment, talk to your cancer team before taking any mushroom supplement. Reishi spore powder can also raise a tumour marker blood test called CA72-4, so tell your team if you take it.
Surgery
The MSD Manual warns that high doses before or during surgery could increase the risk of bleeding. Stop reishi two weeks before planned surgery, and tell your surgeon or anaesthetist you’ve been taking it.
Pregnancy and breastfeeding
Reishi’s safety in pregnancy and breastfeeding hasn’t been properly studied, so avoid it. We don’t recommend our products during pregnancy or breastfeeding. Our products are for adults (18+) only.
Is reishi safe to take every day?
For most healthy adults, taking reishi daily at the amount on the label appears to be well tolerated. The trials give a sense of how far that evidence goes:
| Trial | Who | Daily amount | How long |
|---|---|---|---|
| Wicks 2007 | 16 healthy adults | 4g extract | 10 days |
| Wachtel-Galor 2004 | 18 healthy adults | 1.44g | 4 weeks |
| Tang 2005 | 132 people with long-term fatigue | 5.4g polysaccharide extract | 8 weeks |
| Chu 2012 | 26 people with borderline blood pressure or cholesterol | 1.44g | 12 weeks |
| Chen 2023 | Healthy adults | Reishi beta-glucan | 84 days |
| Klupp 2016 | 84 people with type 2 diabetes | 3g | 16 weeks |
So the longest controlled trials ran for about four months. Longer daily use hasn’t been studied well. If you take reishi for months at a time, take medicines regularly, or have a long-term health condition, mention it to your GP or pharmacist at your next review.
Dosage and the best time to take it
- Amount: doses vary widely depending on whether it’s dried mushroom, powder or a concentrated extract. In trials, daily amounts ranged from about 0.5g to 5.4g, depending on the preparation. Follow the label rather than general figures.
- Time of day: most people take reishi in the evening, as part of a wind-down routine.
- Consistency: trials ran for weeks, so take it daily for at least four weeks before judging it.
- Before bed: many people have it as a warm drink an hour or so before bed.
Ways to take reishi
| Form | Pros | Cons |
|---|---|---|
| Tea from dried slices | Traditional | Very bitter; needs long simmering |
| Capsules | No taste, exact amount | Less of a ritual |
| Powder in a drink | Easy to mix | Bitter unless blended |
| Reishi hot chocolate | Tastes like cocoa, not mushroom | Check the sugar content; cacao contains a little natural caffeine |
Our Reishi Mushroom Adaptogenic Complex is a reishi hot chocolate: reishi mushroom extract with cacao, maca, coconut milk powder and coconut sugar, so it tastes like hot chocolate. Stir a scoop into warm milk or water in the evening. Cacao naturally contains a small amount of caffeine, so if you’re very sensitive to caffeine, have it earlier in the evening; our healthy hot chocolate guide explains how much is in a cup. See also reishi cacao, mushroom tea and our alcohol-free nightcaps.
Is reishi legal in the UK?
Yes. Reishi is sold legally in the UK as a food and food supplement. It contains no controlled substances. Choose a product that states the part used (fruiting body or mycelium) and the extract strength, and that’s tested for contaminants. For other mushrooms, see our adaptogenic mushrooms guide and lion’s mane vs reishi vs cordyceps.
FAQs
What is reishi mushroom good for?
It’s mostly used as an evening wind-down ritual. A small trial found benefits for long-term fatigue, but evidence for heart health and cancer is lacking.
When is the best time to take reishi?
Most people take it in the evening, often as a warm drink an hour or so before bed.
Is reishi safe to take every day?
For most healthy adults, yes, following the label. The longest controlled trials ran for about four months, so longer daily use is less well studied. Avoid it in pregnancy, and check with a pharmacist if you take blood thinners, blood pressure or diabetes medicines.
Does reishi make you sleepy?
Some people find it relaxing in the evening, but there’s little good human research on reishi and sleep.
Is reishi psychedelic?
No. Reishi contains no psilocybin and isn’t psychoactive.
Can reishi damage your liver?
Rarely. There are case reports of liver injury with reishi powder. Stop and see a GP if you notice yellow skin or eyes or dark pee.
What are the negative effects of reishi?
The most common are dry mouth, an upset stomach and dizziness. Itching, rash, headache and nosebleeds are less common. Rarely, liver injury has been reported with reishi powder, and reishi may add to the effects of blood thinners.
Who should not take reishi?
Avoid it if you’re pregnant or breastfeeding, have a bleeding disorder, low blood pressure or liver disease, take immunosuppressants, or have surgery planned in the next two weeks. If you take blood thinners, blood pressure or diabetes medicines, or are having cancer treatment, ask your GP or pharmacist first.
Does reishi interact with medication?
It may. Reishi may slow blood clotting, so take care with blood thinners. It may also add to blood pressure and diabetes medicines, may not be safe with immunosuppressants, and can affect some cancer treatments and blood tests. Check with your pharmacist before starting it.
Can reishi cause insomnia?
Trouble sleeping has been reported as a minor side effect in one cancer trial, even though most people take reishi in the evening to wind down. If it seems to keep you awake, try it earlier or stop.
Is reishi extract safer than reishi powder?
The published liver cases involved reishi powder, taken for one to two months, often alongside other medicines or alcohol. The MSD Manual suggests extract taken for up to a year might be safe. Whatever the form, follow the label and stop if you notice signs of liver trouble.
Sources
- Tang W et al. A Ganoderma lucidum polysaccharide extract in neurasthenia. J Med Food, 2005.
- Klupp NL et al. Ganoderma lucidum mushroom for the treatment of cardiovascular risk factors. Cochrane Database Syst Rev, 2015.
- Jin X et al. Ganoderma lucidum (reishi mushroom) for cancer treatment. Cochrane Database Syst Rev, 2016.
- Wanmuang H et al. Fatal fulminant hepatitis associated with Ganoderma lucidum mushroom powder. J Med Assoc Thai, 2007.
- Yuen MF et al. Hepatotoxicity due to a formulation of Ganoderma lucidum (lingzhi). J Hepatol, 2004.
- Guedikian R et al. Ganoderma lingzhi (reishi mushroom)-induced acute liver injury in the setting of alcohol use. Cureus, 2023.
- Wicks SM et al. Safety and tolerability of Ganoderma lucidum in healthy subjects. Am J Chin Med, 2007.
- Wachtel-Galor S et al. Ganoderma lucidum: biomarker responses in a controlled human supplementation study. Br J Nutr, 2004.
- Chu TT et al. Study of potential cardioprotective effects of Ganoderma lucidum (lingzhi). Br J Nutr, 2012.
- Klupp NL et al. A randomised, placebo-controlled trial of Ganoderma lucidum for cardiovascular risk factors of metabolic syndrome. Sci Rep, 2016.
- Chen SN et al. Immune modulation by beta-glucan derived from Ganoderma lucidum in healthy adult volunteers. Foods, 2023.
- Zhao H et al. Spore powder of Ganoderma lucidum and cancer-related fatigue in breast cancer patients. Evid Based Complement Alternat Med, 2012.
- Mitra S et al. Ganoderma lucidum supplementation on psychological stress and fitness in female college students. Int J Med Mushrooms, 2024.
- Pazzi F et al. Ganoderma lucidum effects on mood and quality of life in women with fibromyalgia. Healthcare, 2020.
- Tao J, Feng KY. Inhibitory effect of Ganoderma lucidum on platelet aggregation. J Tongji Med Univ, 1990.
- MSD Manual (Consumer Version). Reishi. Reviewed July 2025.
- Memorial Sloan Kettering Cancer Center. Reishi mushroom.
- National Cancer Institute. Medicinal mushrooms (PDQ).
