Lion's mane side effects and safety

What are the side effects of lion's mane?

"It's a mushroom, so it's fine, right?" It's a fair question to ask before you take anything every day. Here's what the research says about lion's mane side effects, and who should check first.

The side effects reported in trials have been mild and uncommon. The ones that come up are stomach discomfort, diarrhoea, nausea and headache [1]. A 2025 systematic review also found that many trials didn't report side effects at all, so the picture isn't complete [1].

In a 16-week trial of 30 older adults with mild memory problems, 7 people on lion's mane and 6 on a placebo had mild stomach discomfort or diarrhoea. None needed treatment [1][2]. That's about the same rate with or without the mushroom.

The longest trial we found ran for 49 weeks, in older adults with early Alzheimer's disease. Three people on lion's mane mycelium left because of abdominal discomfort, nausea or a skin rash, against one on the placebo with nausea. The researchers said they couldn't be sure the capsules caused these, as many of the group took other medicines [3].

Is lion's mane safe?

For most adults, the evidence so far looks reassuring Moderate. Lion's mane is eaten as a food mushroom, and the US LiverTox database says it is generally recognised as safe [4].

Most trials had fewer than 50 people and ran for weeks rather than years [1]. The highest amount tested was 10 g a day, baked into muffins for 4 weeks, with no side effects reported [1]. Our page of lion's mane studies lists the trials in people, with their doses and lengths.

So the short answer is that it looks safe for healthy adults at the amounts studied.

Can lion's mane cause an allergic reaction?

Yes, though it's rare. One person had anaphylaxis, a severe allergic reaction, after eating fresh lion's mane [5].

One serious case was a 63-year-old man in Japan. He needed intensive care for a lung reaction, and tests linked it to a lion's mane extract he'd been taking for about 4 months. He recovered with treatment [6].

If you're allergic to other mushrooms or moulds, ask your GP or pharmacist before you try it.

Is lion's mane bad for your liver?

There's no sign of it. LiverTox rates lion's mane an unlikely cause of liver injury, and says it hasn't been linked to raised liver enzymes or to any case of liver injury [4].

One report described liver damage in a woman taking a mushroom blend with lion's mane in it. The authors linked it to a different mushroom in the blend, Agaricus blazei [8]. That's why it's worth knowing exactly what's in a mushroom product before you take it.

Can you take lion's mane with medicines?

We found no study that has tested lion's mane alongside any medicine, including antidepressants such as sertraline. So there's no evidence either way, rather than evidence that it's safe.

In a lab study on human blood, hot-water extracts of lion's mane and seven other mushrooms had some effect on platelets, the cells that help blood clot. None of them changed clotting times [9]. We found no study testing whether that matters in people. If you take blood thinners, diabetes medicines or antidepressants, check with your GP or pharmacist first.

Who should not take lion's mane?

• People who are pregnant or breastfeeding, as no trials have included them. Health Canada asks people to check with a health professional first [10].
• Anyone allergic to mushrooms, or who has reacted to lion's mane before.
• People taking regular medicines, until they've asked their GP or pharmacist.
• Children, as Health Canada's limits cover adults 18 and over [10].

How much lion's mane is too much?

There's no UK upper limit. Health Canada, the only regulator we found that sets one, lets licensed supplements provide up to 2.8 g of dried lion's mane a day as a powder. For water extracts, the limit is an extract made from up to 12 g of dried mushroom a day [10].

Trials have mostly used about 1 to 3 g of dried mushroom a day, and up to 10 g in food [1][2][3]. Our guide to when to take lion's mane covers doses and timing in detail. So stick to the amount on your label, and don't stack several lion's mane products together.

Where Nooroots fits

Nooroots Ashwagandha + Lion's Mane pairs lion's mane fruiting body extract with KSM-66 ashwagandha root extract, in two caffeine-free capsules a day. It's made for calm focus and calm resilience on demanding days. Our guide to lion's mane covers what the mushroom is and what the trials have looked at.

Frequently asked questions

Can I take lion's mane every day?

Trials have given it every day for up to 49 weeks, and side effects were mild and uncommon. Stick to the amount on the label, and stop if you notice a rash or stomach upset [1][3].

Can lion's mane cause headaches?

It's possible, though uncommon. A 2025 review listed headache, along with stomach discomfort and allergic reactions, as possible side effects [1].

Can lion's mane cause anxiety?

We found no trial that reported anxiety as a side effect of lion's mane. If you feel worse on any supplement, stop taking it and speak to your GP [1].

Will lion's mane keep me awake?

Trials haven't reported poor sleep as a side effect of lion's mane. A lion's mane coffee contains caffeine from the coffee, so check the label if you drink it late in the day [1].

Are there long-term side effects of lion's mane?

The longest trial we found lasted 49 weeks, and the side effects it found were stomach discomfort, nausea and a rash in a few people. We found no study of use over several years [3].

Is lion's mane safe for your liver?

The US LiverTox database rates it an unlikely cause of liver injury. It says lion's mane hasn't been linked to raised liver enzymes or to cases of liver injury [4].

Read more in our guide to lion's mane and ashwagandha together, which covers taking the two at once.

References

Every study here is listed so you can read it yourself. This guide is for general information and doesn't replace advice from your GP or pharmacist. We check it again at least every six months.

1. Menon A, Jalal A, Arshad Z, Nawaz FA, Kashyap R (2025). Benefits, side effects, and uses of Hericium erinaceus as a supplement: a systematic review. Frontiers in Nutrition 12: 1641246. PMID 40959699
2. Mori K, Inatomi S, Ouchi K, Azumi Y, Tuchida T (2009). Improving effects of the mushroom Yamabushitake (Hericium erinaceus) on mild cognitive impairment: a double-blind placebo-controlled clinical trial. Phytotherapy Research 23(3): 367–372. PMID 18844328
3. Li IC, Chang HH, Lin CH, et al. (2020). Prevention of early Alzheimer's disease by erinacine A-enriched Hericium erinaceus mycelia pilot double-blind placebo-controlled study. Frontiers in Aging Neuroscience 12: 155. PMID 32581767
4. LiverTox (updated 5 January 2024). Lion's mane. LiverTox: clinical and research information on drug-induced liver injury. US National Institute of Diabetes and Digestive and Kidney Diseases. PMID 38289992
5. Muhanna M, Lund I, Bromberg M, et al. (2024). ALSUntangled #73: Lion's Mane. Amyotrophic Lateral Sclerosis and Frontotemporal Degeneration 25(3–4): 420–423. PMID 38141002
6. Nakatsugawa M, Takahashi H, Takezawa C, et al. (2003). Hericium erinaceum (yamabushitake) extract-induced acute respiratory distress syndrome monitored by serum surfactant proteins. Internal Medicine 42(12): 1219–1222. PMID 14714963
7. NHS (reviewed 21 June 2023). Anaphylaxis. nhs.uk/conditions/anaphylaxis
8. Strobbe G, Jeanjacquot M, Potey C, Carnot A, Marliot G (2025). Grade 3 cytolysis in a patient with metastatic colorectal cancer consuming a mushroom powder-based alternative therapy. Journal of Oncology Pharmacy Practice 31(2): 329–335. PMID 39223928
9. Poniedziałek B, Siwulski M, Wiater A, et al. (2019). The effect of mushroom extracts on human platelet and blood coagulation: in vitro screening of eight edible species. Nutrients 11(12): 3040. PMID 31842490
10. Health Canada (31 October 2025). Mushrooms. Natural Health Products Ingredients Database monograph. Natural and Non-prescription Health Products Directorate. webprod.hc-sc.gc.ca