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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, 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, people on online forums have reported anxiety, panic, low mood, poor sleep, depersonalisation, anhedonia, emotional blunting and low libido while taking lion's mane, most also disclosing another plausible cause; a PubMed search pairing lion's mane with those terms returned no records on 11 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.
What are the side effects of lion's mane?
From the trials: a mild stomach, a headache, and allergic reactions in people sensitive to mushrooms; the published cases are a contact rash in a grower 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, none ran beyond a year, and none included people on psychiatric medicines. 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. Nothing of that kind: no trial measured these outcomes, included people on psychiatric medicines or ran beyond 49 weeks, and PubMed holds no record pairing lion's mane with anhedonia, emotional blunting or depersonalisation. The one placebo-controlled mood trial, 30 menopausal women for four weeks, found nothing worse than placebo.6 What follows. Reports are not a rate, and absence from PubMed is not absence from life. Nothing documented supports lasting harm, and nothing documented rules it out. People with a history of panic or depression, or on psychiatric medicines, have most reason for caution, and 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 trial has included them and there is no safety data. 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 themselves.
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".
| Medicine (UK generic names) | What is known | Status | What to do |
|---|---|---|---|
| Parkinson's medicines: co-careldopa, co-beneldopa; rasagiline, selegiline, safinamide | No human study; animal and cell work only; an 80-person trial registered in 2020 has not reported | Unstudied | Tell your Parkinson's nurse or pharmacist before starting; do not adjust the medicine |
| Anticoagulants and antiplatelets: apixaban, rivaroxaban, edoxaban, warfarin; aspirin, clopidogrel, ticagrelor; surgery | No human study. One compound, hericenone B, blocked platelet clumping in rabbit platelets in the laboratory7 | Theoretical | Tell the clinic or GP; warfarin users keep INR checks as scheduled; report unusual bruising or bleeding; mention it before surgery |
| Antidepressants: sertraline, citalopram, fluoxetine, venlafaxine, mirtazapine, amitriptyline | No study; most forum mood reports came from people on one of these or with a mood disorder | Unstudied | Tell your GP or pharmacist; if mood changes, stop the supplement, never the antidepressant |
| ADHD medicines: methylphenidate, lisdexamfetamine, dexamfetamine, atomoxetine | No study; stimulants were a disclosed factor in several anxiety and panic reports | Unstudied | Tell the prescriber; do not start both in the same month |
| Diabetes medicines: metformin, gliclazide, insulin and the newer classes | No human glucose trial; animal data only | Unstudied | Tell the diabetes team about any supplement |
| Immunosuppressants, biologics, chemotherapy, immunotherapy | No lion's mane study. Fungal beta-glucans change immune markers in trials; one cancer patient on a mixed mushroom powder had a liver-enzyme rise that settled on stopping8, 9 | Theoretical | Ask the specialist or oncology pharmacist first |
| Hormone therapies: HRT, tamoxifen, letrozole, anastrozole, the pill | No study; lion's mane contains no hormone | Unstudied | Tell the clinic or oncology pharmacist first |
The cross-species table is on the side effects of mushroom supplements. Already taking both? Tell the pharmacist.
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. Lion's mane contains no hormone. The forum theory that it blocks the enzyme behind male-pattern hair loss traces to other forum posts, not to any published study. Low libido appears in the forum reports, usually alongside low mood; a persistent change in libido or erectile function 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 two cannot be separated.1, 8 Dark urine, pale stools or yellowing mean stop and see a GP. Blood pressure and heart: no trial measured them, 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 a week or two 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. To tell the difference: stop for four weeks, score two or three things (sleep, a work task, a mood rating), restart at the same dose for eight weeks, and compare. 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; do not stop any prescribed medicine. For new anxiety, panic, low mood, feeling detached or unreal, 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 at any hour.10 Then report it through the MHRA Yellow Card scheme, which accepts public reports on food supplements; it is the route by which a reported reaction becomes a counted one.11
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 trial has included anyone under 18, so there is no 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
- Mori K, et al. Improving effects of the mushroom Yamabushitake (Hericium erinaceus) on mild cognitive impairment. Phytotherapy Research, 2009. PubMed 18844328.
- Grozier CD, et al. Four weeks of Hericium erinaceus supplementation does not impact markers of metabolic flexibility or cognition. International Journal of Exercise Science, 2022. PubMed 36582308.
- Li IC, et al. Prevention of early Alzheimer's disease by erinacine A-enriched Hericium erinaceus mycelia: pilot double-blind placebo-controlled study. Frontiers in Aging Neuroscience, 2020. PubMed 32581767.
- Menon A, et al. Benefits, side effects, and uses of Hericium erinaceus as a supplement: a systematic review. Frontiers in Nutrition, 2025. PubMed 40959699.
- Docherty S, et al. Acute and chronic effects of lion's mane supplementation on cognitive function, stress and mood in young adults. Nutrients, 2023. PubMed 38004235.
- Nagano M, et al. Reduction of depression and anxiety by 4 weeks Hericium erinaceus intake. Biomedical Research, 2010. PubMed 20834180.
- Mori K, et al. Inhibitory effect of hericenone B from Hericium erinaceus on collagen-induced platelet aggregation. Phytomedicine, 2010. PubMed 20637576.
- Strobbe G, et al. Grade 3 cytolysis in a patient with metastatic colorectal cancer consuming a mushroom powder. Journal of Oncology Pharmacy Practice, 2025. PubMed 39223928.
- Vlassopoulou M, et al. Effects of fungal beta-glucans on health: a systematic review of randomized controlled trials. Food and Function, 2021. PubMed 33876798.
- NHS. Help for suicidal thoughts. nhs.uk/mental-health/feelings-symptoms-behaviours/behaviours/help-for-suicidal-thoughts.
- MHRA. Yellow Card: report a suspected side effect. yellowcard.mhra.gov.uk.
- Maes MF, et al. Occupational allergic contact dermatitis from the mushroom white pom pom (Hericium erinaceum). Contact Dermatitis, 1999. PubMed 10344494.
- Muhanna M, et al. ALSUntangled #73: lion's mane. Amyotrophic Lateral Sclerosis and Frontotemporal Degeneration, 2024. PubMed 38141002.
- Dimitrov P, et al. Nutrients, 2026 (uncontrolled study of a Hericium biomass supplement in 147 children). PubMed 41599861.
This article is general information, not medical advice. Lion's mane has no authorised health claim in Great Britain and has not been tested in pregnancy, breastfeeding or childhood; if you take any regular medicine, or have a history of panic, depression or psychosis, ask a pharmacist or GP before starting it, and never stop or change a prescribed medicine on the strength of a supplement.
