Lion's Mane Side Effects: Reports, Trials and Who Should Take Care

In the published trials of lion's mane, to 10 g a day for four weeks and about 1 g a day for 49 weeks in a supplier-run pilot, no serious adverse effect was recorded; four people in the 49-week trial stopped for stomach discomfort, nausea or a rash, and the 2025 systematic review lists stomach discomfort, headache and allergic reactions as the side effects to expect, adding that trials "commonly" fail to report them.^{1, 2, 3, 4} Separately, forum users have reported anxiety, panic, low mood, poor sleep, depersonalisation, anhedonia, emotional blunting and low libido while taking lion's mane, most also disclosing another cause; a PubMed search pairing lion's mane with those terms returned no records on 29 October 2026. People with a history of panic or depression, on psychiatric medicines, pregnant, breastfeeding or under 18 should ask before starting. This is the lion's mane safety page of our guide to whether mushroom supplements work.

Sources checked on 29 October 2026.

What are the side effects of lion's mane?

From the trials: a mild stomach, a headache, and allergic reactions; the published cases are an occupational contact rash and one anaphylaxis after fresh lion's mane.^{12, 13} In the 16-week trial of 30 older adults at 3 g a day, blood tests showed no adverse change; four weeks at 10 g a day produced nothing of note in 24 healthy adults; 49 weeks of a standardised mycelium in early dementia was described as safe; and the 28-day trial in 41 young adults reported "null and limited negative findings" alongside its one positive result.^{1, 2, 3, 5} The number studied is in the low hundreds. How lion's mane makes you feel covers the everyday reports.

Is lion's mane safe? What the forum reports say and what has been studied

What has been reported. In the forum threads read, about 14 people attributed an adverse experience to lion's mane: anxiety or panic (5), low mood or suicidal thoughts (4), depersonalisation or derealisation (3), insomnia (2), and single reports of anhedonia, tearfulness and gut upset. Most disclosed something else: an existing anxiety or depressive disorder, antidepressants or other psychiatric medicines, ADHD stimulants, a stack of supplements, or a doubled or sublingual dose. What has been studied. Little: two small placebo-controlled trials, 30 menopausal women for four weeks and 41 young adults for 28 days, scored mood, stress or sleep and found no mood or stress score worse than placebo; none included people on psychiatric medicines or ran beyond 49 weeks.^{5, 6} What follows. Reports are not a rate, and absence from PubMed is not absence from life; nothing documented supports lasting harm, and nothing rules it out. Anyone who feels unwell should stop and speak to a GP or pharmacist. The psychedelic confusion behind some threads is answered on does lion's mane get you high.

Who should avoid lion's mane?

Anyone with a mushroom allergy, because allergic reactions are among the documented side effects.⁴ Anyone pregnant or breastfeeding, and anyone under 18, because no controlled trial has included them. Anyone with a history of panic attacks, depression or psychosis, or on a psychiatric medicine. Anyone on an anticoagulant, antiplatelet, transplant medicine, biologic or cancer treatment, until they have asked the clinic or pharmacist. And anyone about to have surgery, who should mention it at the pre-operative assessment. What lion's mane is good for covers the trials.

What should you not mix lion's mane with?

No human interaction study of lion's mane exists, so each row is marked known, theoretical or unstudied; "what to do" is never "stop the medicine".

The cross-species table is on the side effects of mushroom supplements.

Does lion's mane affect testosterone, libido or hair?

No human study has measured testosterone, oestrogen, libido, fertility or hair in anyone taking lion's mane, so "does it lower testosterone" and "does it cause hair loss" share one answer: not measured, in either direction. The forum theory that it blocks the enzyme behind male-pattern hair loss traces to other forum posts, not to any study. Low libido appears in the forum reports, usually alongside low mood; a persistent change is a GP matter.

Does lion's mane affect the liver, blood pressure or weight?

Liver: the 16-week trial found no adverse change in blood tests, and the one published case is a cancer patient whose liver enzymes rose on a powder containing lion's mane and another mushroom, then settled when it stopped; the authors attributed it to the other mushroom, Agaricus blazei.^{1, 8} Dark urine, pale stools or yellowing mean stop and see a GP. Blood pressure and heart: no trial reports a change, so people with heart disease tell their GP. Weight: no trial reported weight gain, and the four-week 10 g trial found no change in how the body used fuel.^{2, 4} Kidneys: no signal in any trial (the high-oxalate mushroom is chaga).

What happens when you stop taking lion's mane?

In the only trial that looked, the cognitive-score gain in 30 older adults disappeared within four weeks of stopping.¹ On forums, brain fog returning after stopping is read as withdrawal by some and proof by others. No trial has described a withdrawal syndrome; the plainer reading is that whatever was there before is still there. Anyone who stopped because they felt unwell should not restart without advice.

What should you do if you feel unwell, and how do you report it?

Stop the supplement, not any prescribed medicine. For new anxiety, panic, low mood, feeling detached, or poor sleep, speak to a GP or pharmacist or call NHS 111. Thoughts of harming yourself are urgent: call 999 or go to A&E if you are in immediate danger, otherwise NHS 111, your GP, or the Samaritans on 116 123.¹⁰ Then report it to your local authority's trading standards or environmental health team, which works with the Food Standards Agency.¹¹

What we don't know

Whether the forum reports reflect the mushroom: no trial has included people on psychiatric medicines or with a history of panic, so nothing confirms or rules them out.^{5, 6} Safety beyond 49 weeks, in pregnancy, in children or with any medicine: untested.^{3, 14} Effects on the liver or clotting in people: the one liver case involved a second mushroom; the platelet finding is laboratory only.^{7, 8}

Frequently asked questions

Is lion's mane safe long term?

Unknown beyond a year: the longest trial ran 49 weeks and most ran 4 to 16, with no serious adverse effect in those windows.^{1, 3}

Can lion's mane cause bloating?

Stomach discomfort is the most consistently listed side effect, so yes for some people; take it with a meal and stop if gut symptoms persist.^{1, 4}

Is lion's mane a blood thinner?

Not in any human study. One compound slowed platelet clumping in a laboratory test, which is why anticoagulant users are asked to tell their clinic.⁷

Can children take lion's mane?

No controlled trial has included anyone under 18, so there is no reliable safety data; it is not recommended for children or teenagers. A 2026 study of 147 children was not randomised or blinded, so it cannot show safety or benefit.¹⁴

Can you drink alcohol with lion's mane, and does it contain alcohol?

No study has looked at the combination; a dried extract contains no meaningful alcohol, a tincture does.

Sources

1. Mori K, et al. Lion's mane (Yamabushitake) in mild cognitive impairment. Randomised placebo-controlled trial, 30 adults, 16 weeks; run by a producer's laboratory. Phytotherapy Research, 2009. PubMed 18844328.
2. Grozier CD, et al. Four weeks of Hericium erinaceus and metabolic flexibility or cognition. Single-blind placebo-controlled trial, 24 adults, 4 weeks; funding not stated. International Journal of Exercise Science, 2022. PubMed 36582308.
3. Li IC, et al. Erinacine A-enriched mycelia in early Alzheimer's disease. Randomised placebo-controlled pilot, 68 enrolled, 49 weeks; supplier-run. Frontiers in Aging Neuroscience, 2020. PubMed 32581767.
4. Menon A, et al. Hericium erinaceus as a supplement. Systematic review, 5 randomised and 3 pilot trials; no commercial funding. Frontiers in Nutrition, 2025. PubMed 40959699.
5. Docherty S, et al. Lion's mane, cognition, stress and mood in young adults. Randomised placebo-controlled pilot, 41 adults, 28 days; product supplied by a producer. Nutrients, 2023. PubMed 38004235.
6. Nagano M, et al. Depression and anxiety after 4 weeks of Hericium erinaceus. Randomised placebo-controlled trial, 30 women, 4 weeks; funding not stated. Biomedical Research, 2010. PubMed 20834180.
7. Mori K, et al. Hericenone B and collagen-induced platelet aggregation. Laboratory study, rabbit and human platelets; publicly funded. Phytomedicine, 2010. PubMed 20637576.
8. Strobbe G, et al. Grade 3 cytolysis in a cancer patient taking a mushroom powder. Case report, 1 patient; no conflict declared. Journal of Oncology Pharmacy Practice, 2025. PubMed 39223928.
9. Vlassopoulou M, et al. Fungal beta-glucans and health. Systematic review, 34 randomised trials. Food and Function, 2021. PubMed 33876798.
10. NHS. Help for suicidal thoughts. Reviewed 26 April 2024; read 29 October 2026. nhs.uk.
11. Food Standards Agency. How to report a food safety or hygiene issue for members of the public. gov.uk.
12. Maes MF, et al. Occupational allergic contact dermatitis from Hericium erinaceum. Case report, 1 patient. Contact Dermatitis, 1999. PubMed 10344494.
13. Muhanna M, et al. ALSUntangled #73: lion's mane. Evidence review. Amyotroph Lateral Scler Frontotemporal Degener, 2024. PubMed 38141002.
14. Dimitrov P, et al. Hericium biomass supplement in children with intellectual disabilities. Uncontrolled observational study, 147 children, 6 to 12 months; no funding declared. Nutrients, 2026. PubMed 41599861.

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General information, not medical advice: with any regular medicine, or a history of panic, depression or psychosis, ask a pharmacist or GP first.