Lion's mane side effects: what is known and who should be cautious?

Short answer: In studies, lion's mane (pom pom mushroom, Hericium erinaceus) was generally well tolerated, and review articles cite mild stomach and intestinal problems as the most common side effect. If you have a mushroom allergy, are pregnant, or take medication, take extra care. Long-term research on supplements is scarce, so stick to the recommended daily dose.

Last updated: October 30, 2026 · Written by Florian Fermin

A customer asked us where the lion's mane in our capsules comes from. The customer had read online about lead and other heavy metals in lion's mane from places including China.

That's a fair question, and it's really part of the safety discussion. So here's both: what's known about side effects, and how to check what's in your product.

Which side effects of lion's mane are reported most often?

The most commonly reported side effects of lion's mane are mild stomach and intestinal problems. In clinical studies, lion's mane was generally well tolerated, with gastrointestinal problems as the most common side effect (Baker & Newman, 2025). A systematic review also mentions headaches and allergic reactions as possible side effects, although side effects are often not reported in studies (Menon et al., 2025).

Users report stomach problems more often when taking it on an empty stomach, but this has not been studied separately. A side effect is an unwanted reaction of the body to something you take. Lion's mane is an edible mushroom that has long been used in cooking in Asia.

What does scientific research say about the safety of lion's mane?

Research into the safety of lion's mane in humans is limited to a few small studies lasting weeks to months. In the best-known study, participants took 3 g of tablets daily for 16 weeks, and the researchers observed no adverse effects in laboratory tests. Long-term safety research spanning several years has not yet been conducted.

That Japanese study included 30 adults aged 50 to 80. Half received lion's mane, and the other half received a placebo (Mori et al., 2009). The lion's mane group took four 250 mg tablets three times a day, containing 96% dried fruiting body powder.

With 15 participants per group, the study is simply too small to detect rare side effects. So, the fact that no side effects were reported in a small study does not mean they never occur. However, there is no evidence of serious problems with short-term use in that specific group.

Who should take extra care when using lion's mane?

Take extra care if you have a mushroom or mold allergy, are pregnant or breastfeeding, take medication, or are due to have surgery soon. Too little safety research has been done in these groups to recommend using lion's mane without consulting your GP or pharmacist.

• If you have a mushroom or mold allergy: It’s best not to use lion's mane.
• During pregnancy and breastfeeding: There is too little safety research, so we advise against using it without consulting your GP or midwife.
• If you take medication: Consult your GP or pharmacist first, especially if you take blood thinners.
• Before surgery: Tell your GP that you use supplements.
• Children: Supplements are not intended for children unless your GP advises otherwise.

Can I safely take lion's mane with blood thinners or other medications?

Whether lion's mane is safe to take with blood thinners or other medications has barely been studied in humans. Interactions cannot be ruled out, so it’s best to consult your GP or pharmacist first. This applies especially to blood thinners and medications you take around the time of surgery.

Bring a list of all the supplements you use, including the amounts. This will help your pharmacist better assess whether a combination is advisable.

Is lion's mane permitted as a food and as a supplement in the EU?

Lion's mane is permitted in the EU as a food and in food supplements, as long as it is the fruiting body. The fruiting body is the mushroom itself, the white clump with spines.

For mycelium, the threadlike network from which the mushroom grows, the novel food status may differ from that of the fruiting body. Therefore, check the EU Novel Food Status Catalogue for each part.

A novel food is a food that was not consumed to a significant degree in the EU before May 1997 and therefore requires European authorization first. Read why this distinction matters in our article about fruiting body vs. mycelium.

How can you use lion's mane to minimize the risk of side effects?

You can minimize the risk of side effects by following the daily dose on the packaging, taking lion's mane with a meal, and choosing a product made from the fruiting body and tested for contaminants. If you use multiple products containing lion's mane, add up the amounts.

• Stick to the daily dose, and also read our article about lion's mane dosage.
• Choose a product that clearly states the species, uses the fruiting body as its source, and has been lab-tested. Read how to read a CoA.
• If you have a sensitive stomach, start with the lowest amount on the label.
• Lion's mane is not a replacement for medication or medical advice.

A certificate of analysis (CoA) is a lab report for each production batch, including measured levels of heavy metals and microbiological contaminants. If you have the same question about lead as that customer, this is the document to ask for. Read more about the mushroom in our article on lion's mane and the facts about lion's mane.

What warnings appear on our lion's mane packaging?

The capsule packaging literally says: "Do not exceed the recommended daily dosage. Consult your doctor before use if you are pregnant, breastfeeding, taking medication, or have a medical condition." The powder and capsules also advise taking lion's mane "preferably during or immediately after a meal." This aligns well with the advice for a sensitive stomach.

The powder carries the same warning, using "you" instead of "you" in the formal sense. All our lion's mane products are made from the fruiting body, not mycelium, and contain no colorants or preservatives. The powder and capsules are also free from fillers, and the capsule shell is made of HPMC.

The raw ingredients come from China, and we have a certificate of analysis (CoA) for every batch, which you can request via support@getgoyu.com. There are no approved health claims for lion's mane itself, so we deliberately avoid promises about what it can do for you.

Summary in 3 points

• The most commonly reported side effects of lion's mane are mild gastrointestinal complaints, so take it with a meal.
• If you have a mushroom allergy, are pregnant or breastfeeding, take medication, or have a planned surgery, consult your doctor or pharmacist first.
• Research consists of small studies lasting weeks to months, so follow the daily dosage on the packaging.

Frequently asked questions

Can lion's mane cause stomach problems?

Yes, review articles list gastrointestinal complaints as the most common side effect. If you have a sensitive stomach, take it with a meal.

Can I use lion's mane if I am pregnant?

There is not enough research on this. Consult your doctor or midwife.

Can I combine lion's mane with medication?

Consult your doctor or pharmacist first, especially if you take blood thinners.

What should I do if I have an allergic reaction to lion's mane?

Stop using it immediately and contact your doctor, especially if you experience shortness of breath or swelling.

Is lion's mane safe for long-term use?

There is little data on this, as most studies lasted from a few weeks to a few months. Follow the daily dosage and consult a professional if in doubt.

References

1. Mori K, Inatomi S, Ouchi K, Azumi Y, Tuchida T (2009). Double-blind, placebo-controlled study of Yamabushitake (Hericium erinaceus) in adults aged 50 to 80 years. Phytotherapy Research, 23(3), 367-372. Europe PMC 18844328
2. Baker JF, Newman SD (2025). Theoretical review article on Hericium erinaceus supplementation alongside medication. Psychopharmacology Bulletin, 55(2), 41-59. Europe PMC 39935672
3. Menon A, Jalal A, Arshad Z, Nawaz FA, Kashyap R (2025). Systematic review of the use and side effects of Hericium erinaceus as a supplement. Frontiers in Nutrition, 12, 1641246. Europe PMC 40959699
4. Packaging text for Lion's Mane Powder and Capsules (back) and usage instructions for Lion's Mane Extract Capsules, accessed October 15, 2026.

You can find all forms of our lion's mane on the buy lion's mane page.

This article is for informational purposes only and is not medical advice. Dietary supplements are not a substitute for a varied and balanced diet and a healthy lifestyle. If in doubt, pregnant, or taking medication, consult your doctor or pharmacist.