Lion’s Mane side effects

Lion’s Mane mushroom supplements are safe, even in very high doses, and are unlikely to cause any side effects. However, if you are currently taking a blood thinner medication or are diabetic, be aware that there are known interactions between Lion’s Mane and these conditions.

What side effects can Lion’s Mane mushroom have?

Lion’s Mane generally isn’t associated with any side effects. A few participants in one study did experience abdominal discomfort, nausea, and skin rash, attributed to the supplement. However, the majority of other human studies report no side effects.

There are few reported incidents of side effects due to Lion’s Mane supplementation. Those that do exist are mild in nature.

Only one study appears to indicate any side effects due to supplementation. In it, four participants dropped out because they experienced abdominal discomfort, nausea, and skin rash [Li 2020]. This was a 49-week, double-blind study evaluating the effects of Lion’s Mane on patients over 50 years of age with mild Alzheimer’s. Subjects in the treatment group took three 350mg capsules per day of methanol extracted liquid-grown mycelium, where each capsule had 5mg/g of erinacine A. The four participants who dropped out represent 8% of the total number of participants in the treatment group. The side effects are possibly related to the intervention, but it can’t be said for certain.

Other research studies conducted on Lion’s Mane using people don’t report any side effects for participants.

High doses of Lion's Mane may interact with resting blood glucose levels, which may be a concern for diabetics. Image shows diabetic medications and blood glucose monitoring devices.

Lion’s Mane and diabetes

High doses of Lion’s Mane fruiting body methanolic extract lowered resting blood glucose levels in diabetic rats. At regular doses (roughly 8g/day for humans), there appears to be no interaction. Nonetheless, it’s advisable to exercise caution and consult a healthcare provider before taking Lion’s Mane if you are diabetic.

You may find warnings online about taking Lion’s Mane if you are diabetic. This is because some studies indicate that Lion’s Mane has an effect on blood glucose. This effect is not yet well understood and few details exist. In fact, only one study indicates this interaction, and it was done on rats.

A methanol extract of Hericium erinaceus fruiting body was injected into 60 rats. Most of these rats had induced diabetes (except for a lucky 12, left as control). The diabetic rats, those who had a fasting blood glucose of 230mg/dl, were divided into four groups: control (no supplementation), 20 mg/kg/day, 100mg/kg/day, or 200mg/kg/day of the extract. Lion’s Mane appeared to be effective in helping the diabetic rats maintain a lower fasting blood sugar level. Those given 100 or 200mg/kg/day consistently maintained a lower fasting blood glucose than the other diabetic rats. This was true after each measurement: after 5, 10, 15, and 20 days of treatment. This is a promising result, indicating that Lion’s Mane may contain compounds that can be used to treat diabetes. However, it also means that diabetics need to exercise caution when taking Lion’s Mane [Wang 2005].

Similar results were observed for diabetic rats given 100 or 200mg/kg of water extract of Lion’s Mane over 28 days [Liang 2013].

For reference, 100mg/kg/day for rats would be 600 mg/kg/day for humans, this corresponds to 40 g/day for a 150 lb (68 kg) person [Nair Jacob 2016]. Similarly, 20mg/kg/day for rats corresponds to 8g/day for humans.

In practice, the vast majority of supplements are orders of magnitude less than this limit, so it is unlikely that most diabetics would experience these interactions with the typical Lion’s Mane supplement.

Lion’s Mane and blood thinners

A compound in Lion’s Mane fruiting body is associated with anticoagulation properties. Exercise caution if you already on a blood thinner medication.

Hericenone B, a compound found only in the fruiting body, inhibits collagen-induced platelet aggregation in human platelets. Platelet aggregation refers to the process wherein platelets (components within blood) join together at the sites of injuries to form blood clots. Thus, hericenone B’s ability to inhibit this activity may make it a useful treatment in thrombosis. Thrombosis is when blood clots block arteries or veins. This can be fatal if it occurs in arteries that send blood to the heart [Mori Kikuchi 2010].

Although this activity in hericenone B is a promising area of research, it also means that those already taking blood thinners (anticoagulants, such as heparin or warfarin) should take special precaution. For these people, the addition of Lion’s Mane can potentially cause health issues such as bruising and bleeding. Its particularly advisable for such individuals to consult with a healthcare provider before taking Lion’s Mane.

Long-term side effects of Lion’s Mane

Can it lower testosterone?

No studies exist suggesting that Lion’s Mane lowers testosterone.

Some believe that Lion’s Mane may affect testosterone levels in the body because of its effects on the brain. Lion’s Mane stimulates neurogenesis and promotes the production of brain-derived neurotrophic factors (BDNF). BDNF modulates the hypothalamus’s hormone signals [Iu 2022]. However, this doesn’t necessarily provide any evidence that Lion’s Mane affects the production of hormones. Thus, this appears to be a speculative claim based on the experiences of some consumers.

Additionally, Lion’s Mane doesn’t appear to influence estrogen levels either. One study using 0.09g/day of H. erinaceus to reduce body fat in menopausal women found that it didn’t influence estrogen [Hiraki 2017].

Is Lion’s Mane safe?

Lion’s Mane mushroom supplements are safe to take, even in high doses. Some concerns exist regarding heavy metal concentrations, but may be easily alleviated by reviewing lab test results from producers.

Does Lion’s Mane mushroom contain heavy metals?

Many Lion’s Mane supplements use farm-grown mushrooms, particularly from China. Responsible mushroom producers will do heavy metal testing and provide these test results to their consumers.

Excessive heavy metal concentration is a concern because wild Chinese mushrooms have been sometimes found to be above the legal limits for zinc, cadmium, and lead. Although this wasn’t the case for Lion’s Mane in this particular study, it nonetheless poses some health concerns [Zhu 2011]. The heavy metals evaluated in the study and their corresponding permissible limits were: copper (Cu) (40 mg/kg), zinc (Zn) (60 mg/kg), iron (Fe) (15mg/kg), manganese (Mn) (400–1,000 mg/kg), cadmium (Cd) (0.30mg/kg), chromium (Cr) (120 mg/kg), nickel (Ni) (recommended daily: 100 and 300 mg/kg), and lead (Pb) (10.0 mg/kg). These values represent the permissible limits allowed in food, according to regulatory agencies or health guidelines.

Most responsible mushroom supplement producers will use farm-grown mushrooms and do heavy metal testing. Consumers may verify those heavy metal tests to ensure these heavy metals are in the acceptable range.

Lion's Mane is safe in high doses, without side effects. This diagram shows that the safety threshold is well above the typical supplement or dosage used in studies.
The chart above demonstrates that the safety of Lion’s Mane has been tested orders of magnitude beyond what the typical person takes. The average capsule contains less than one gram (generally 250 – 1,000 mg) of Lion’s Mane powder or extract. Studies use anywhere from 1g/day to 12g/day. Above, we depict three studies with effective results, and their doses were 3-11g/day. Several tests have been performed on rats to evaluate the toxicity level of Lion’s Mane, but none has been found. Even at very large doses (which are equivalent to 612g/day for humans, extrapolated from the amount given to rats), Lion’s Mane causes no side effects or negative outcomes in animal subjects.

Is Lion’s Mane safe in high doses?

Lion’s Mane is safe to take in high doses, upwards of hundreds of grams a day. This is based on toxicology tests done on rats.

The toxicity of substances are evaluated based on the measurable and observable effects using lab animals. Through evidence of this nature, we know Lion’s Mane is safe even in large doses. Several studies on rats reveal that upwards of 3g/kg/day of Lion’s Mane poses no adverse effects [Park 2008] [Li 2014] [Lakshmanan 2016].

For rats given a water extract mixture of Panax ginseng and Hericium erinaceum over 28 days, no adverse effects were observed. The rats were given doses of 1250, 2500 and 5000 mg/kg/day. There were no differences in body weight, organ weights, measures of blood, nor any visible changes [Park 2008].

Another study evaluated the toxicity of Hericium erinaceum mycelium enriched with 5mg/g of erinacine A (a particularly beneficial compound in the mycelium, associated with brain-boosting health benefits). No matter the dose given to the rats (1, 2, or 3g/kg/day), no adverse effects or health changes were observed [Li 2014].

A long-term study, observing changes over 90 days for a water extract of Hericium erinaceum, also found no adverse effects. Rats given 250, 500, or 1000mg/kg had no observed or measured changes in health (no change in body weight, bloodwork, organ weights, etc.) [Lakshmanan 2016].

For reference, 3g/kg/day for mice would be 9,000 mg/kg/day for humans, this corresponds to 612 g/day for a 150 lb (68 kg) person [Nair Jacob 2016]. This is orders of magnitude greater than the dosage generally used in human studies. For example [Vigna 2019] used 3.6g/day of capsules, [Nagano 2010] used 2g/day of pure fruiting body, [Mori 2009] used 3g/day of air-dried and powdered fruiting body, and [Inanaga 2014], a case study, used 11.7g / day of Amyloban 3399.

View our dosing guide for more details on how much Lion’s Mane to take.


Lion’s Mane is safe to take for most people, with no known toxic dosage. Side effects are rarely reported. For diabetics or those taking blood thinning medication, there are potential interactions with Lion’s Mane and these conditions.

It’s always advisable to first consult with a healthcare provider before taking a new supplement, particularly if you already have a pre-existing condition such as diabetes.

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