Across 1,188 first-hand reports, people mentioned a side effect 98 times (about 8 per 100 reports). The most common: anxiety, libido loss, vivid dreams. User reports show what people notice — they can't tell you whether Lion's Mane is safe for you.
“I would strongly suggest against getting lion's mane. It can worsen your anxiety very much.”
“I went for a walk with my wife today and proclaimed that I could actually feel the wind on my face.”
“But then, I decided to move up to 2000mg and I can confidently say that I had diminished my gains and was in the land of increased side effects.”
“Adding Lion's Mane to my stack has vastly improved my intellectual capacity.”
“Lion's mane has led to permanent side effects for me. More than five months after quitting I'm still not back to normal, and I doubt I ever will.”
“Lion's mane was great as it drastically increased the vividness of my dreams... but didn't notice any difference in my school performance whatsoever.”
Conclusion: Although commonly unreported, potential side effects of HE include stomach discomfort, headache, and allergic reactions. https://www.crd.york.ac.uk/PROSPERO/view/CRD42024571250.