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Ingredient guide

Is lion's mane safe? Side effects reported in studies

Written by the Full Measure editorial team, which sells supplements. Approved for publication by the Full Measure owners. Updated .

Drafted with AI assistance from the sources listed below. How we write these

Quick answer

In trials lasting weeks to months, lion's mane mostly caused mild stomach upset, reported by under 10% of people. NIH's LiverTox rates it an unlikely cause of liver injury. Rare allergic reactions have been reported, including one severe lung reaction, and we found no safety studies in pregnancy or breastfeeding.1,2,3

Key facts

  • In a 49-week trial, 3 of the people taking lion's mane stopped because of side effects, against 1 taking placebo.2
  • Laboratory tests showed no adverse effect in a 16-week trial of about 3 g a day.4
  • No side effects were reported on the lion's mane day of a 40-person single-dose trial.5
  • FDA stopped evaluating the only GRAS notice for a lion's mane ingredient in 2023, at the company's request.6

Side effects reported in trials

Stomach discomfort, nausea or diarrhea, reported by under 10% of people in longer trials.1,2

Skin rash. In a 49-week trial, 3 people taking lion's mane stopped because of stomach discomfort, nausea or a rash, against 1 on placebo who stopped because of nausea.2

Headache and allergic reactions are listed as possible side effects in a 2025 systematic review, which notes that side effects often go unreported.7

How often these happen is hard to pin down. LiverTox notes that several trials did not mention side effects at all, and the trials were small, so an effect that troubles one person in a hundred could easily be missed.1,7

Rare but serious: allergic reactions

Rare: a severe immune reaction in the lungs. A 63-year-old man in Japan developed acute respiratory distress syndrome that doctors linked to a lion's mane extract he had been taking. Tests showed a strong reaction to the extract, and he recovered with steroid treatment on a ventilator.3

Anyone who has reacted to mushrooms before should not take lion's mane. Stop it and get medical help at once for wheezing, breathlessness, swelling of the face or a spreading rash.

Liver and kidneys

LiverTox finds no link between lion's mane and raised liver enzymes or liver injury in people, and rates it an unlikely cause. In rats, an erinacine A-enriched mycelium at up to 3 g per kg of body weight a day for 28 days caused no changes in blood or urine tests.1,8

We found no study of lion's mane in people with kidney disease. If you have kidney or liver disease, ask your doctor before starting it.

Mood and mental side effects

People often ask whether lion's mane can cause anxiety or low mood. None of the trials we read listed a mood problem among their side effects, and the small studies that measured mood did not report it getting worse. A 2025 systematic review of side effects names stomach discomfort, headache and allergic reactions, not mood changes.7,9,10

That is not proof it cannot happen. If your mood changes after starting any supplement, stop it and talk to your doctor, and do not use lion's mane in place of care for depression or anxiety.

Pregnancy, breastfeeding and children

We found no human study of lion's mane in pregnancy or breastfeeding, and no placebo-controlled trial in children. The only pregnancy data are from rats: in a study by a mycelium maker, pregnant rats given very large daily amounts had fetuses that did not differ from those of untreated rats. Animal results do not show safety in people, so ask your doctor first.11

Medicines

The official sources we checked, including NIH's LiverTox and the DailyMed labels of common blood thinners, antidepressants and blood pressure medicines, do not list an interaction with lion's mane. That is not proof that it mixes well with every medicine.1

One lion's mane compound, hericenone B, slowed platelet clumping in laboratory tests. Ask your doctor or pharmacist first if you take a blood thinner or antiplatelet medicine, and tell your surgical team before any operation.12

How much is too much

No upper limit is set. Trials have used up to 10 g a day for 4 weeks in young adults, and about 3 g a day for 16 weeks in older adults, where laboratory tests showed no adverse effect. NIH's LiverTox rates lion's mane an unlikely cause of liver injury. Daily use beyond a few months has been studied only in older adults under medical care.1,2,4,13

What regulators have reviewed

FDA's inventory of GRAS notices lists one lion's mane ingredient, a beta-glucan from one lion's mane strain. In 2023 FDA stopped evaluating it at the company's request, so FDA reached no conclusion on it.6

That notice covered one purified ingredient, not the whole mushroom. LiverTox describes lion's mane itself as generally recognized as safe, reflecting its long use as a food.1,6

Questions people ask

Can lion's mane cause liver damage?

LiverTox rates lion's mane an unlikely cause of liver injury and has found no case linked to it. Laboratory tests stayed normal in a 16-week trial of about 3 g a day.1,4

Are the side effects different for women and men?

None of the trials we read reported a difference. Women were 14 of the 20 people taking lion's mane in the 49-week trial, where the side effects were stomach discomfort, nausea and rash.2

Who should not take lion's mane?

Anyone who has had an allergic reaction to it or to other mushrooms. People who are pregnant, breastfeeding, under 18, taking a blood thinner or due for surgery should ask a doctor first.3,12

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Sources

  1. LiverTox: Clinical and Research Information on Drug-Induced Liver Injury. Lion's Mane. Bethesda (MD): National Institute of Diabetes and Digestive and Kidney Diseases. Last update January 5, 2024. Opened 2026-10-01.
  2. Li IC, Chang HH, Lin CH, et al. Prevention of early Alzheimer's disease by erinacine A-enriched Hericium erinaceus mycelia pilot double-blind placebo-controlled study. Front Aging Neurosci. 2020;12:155. Opened 2026-10-07.
  3. Nakatsugawa M, Takahashi H, Takezawa C, et al. Hericium erinaceum (yamabushitake) extract-induced acute respiratory distress syndrome monitored by serum surfactant proteins. Intern Med. 2003;42(12):1219-1222. Opened 2026-10-07.
  4. Mori K, Inatomi S, Ouchi K, Azumi Y, Tuchida T. Improving effects of the mushroom Yamabushitake (Hericium erinaceus) on mild cognitive impairment: a double-blind placebo-controlled clinical trial. Phytother Res. 2009;23(3):367-372. Opened 2026-10-07.
  5. La Monica MB, Raub B, Ziegenfuss EJ, et al. Acute effects of naturally occurring guayusa tea and Nordic lion's mane extracts on cognitive performance. Nutrients. 2023;15(24):5018. Opened 2026-10-07.
  6. U.S. Food and Drug Administration. GRAS Notice Inventory: GRN No. 1124, beta-glucans from Hericium erinaceus strain BCRC 35669. Closed September 28, 2023. Opened 2026-10-07.
  7. Menon A, Jalal A, Arshad Z, Nawaz FA, Kashyap R. Benefits, side effects, and uses of Hericium erinaceus as a supplement: a systematic review. Front Nutr. 2025;12:1641246. Opened 2026-10-07.
  8. Li IC, Chen YL, Lee LY, et al. Evaluation of the toxicological safety of erinacine A-enriched Hericium erinaceus in a 28-day oral feeding study in Sprague-Dawley rats. Food Chem Toxicol. 2014;70:61-67. Opened 2026-10-07.
  9. Nagano M, Shimizu K, Kondo R, et al. Reduction of depression and anxiety by 4 weeks Hericium erinaceus intake. Biomed Res. 2010;31(4):231-237. Opened 2026-10-07.
  10. Docherty S, Doughty FL, Smith EF. The acute and chronic effects of lion's mane mushroom supplementation on cognitive function, stress and mood in young adults: a double-blind, parallel groups, pilot study. Nutrients. 2023;15(22):4842. Opened 2026-10-07.
  11. Li IC, Chen WP, Chen YP, Lee LY, Tsai YT, Chen CC. Acute and developmental toxicity assessment of erincine A-enriched Hericium erinaceus mycelia in Sprague-Dawley rats. Drug Chem Toxicol. 2018;41(4):459-464. Opened 2026-10-07.
  12. Mori K, Kikuchi H, Obara Y, et al. Inhibitory effect of hericenone B from Hericium erinaceus on collagen-induced platelet aggregation. Phytomedicine. 2010;17(14):1082-1085. Opened 2026-10-07.
  13. Grozier CD, Alves VA, Killen LG, Simpson JD, O'Neal EK, Waldman HS. Four weeks of Hericium erinaceus supplementation does not impact markers of metabolic flexibility or cognition. Int J Exerc Sci. 2022;15(2):1366-1380. Opened 2026-10-07.

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.