Huperzine A is a compound from the Chinese herb Huperzia serrata that blocks the enzyme that breaks down acetylcholine (a cholinesterase inhibitor), the same way some Alzheimer's drugs work. It is sold in memory and "nootropic" supplements and has been studied mainly in Alzheimer's disease.
Also known as: Huperzia serrata extract, HupA.
Huperzine A has no intake value or upper limit, and there is no NIH fact sheet for it. The US phase II trial (Rafii 2011) used 200 mcg or 400 mcg twice a day for at least 16 weeks. These are study protocols, not a recommendation.
It is sold in the US as a dietary supplement. Under the 1994 dietary supplement law (DSHEA), FDA does not approve dietary supplements before they are marketed, and the maker, not FDA, is responsible for safety and labeling. A 2023 review (Jędrejko) notes that the European Commission treats huperzine A as an unauthorized food and supplement ingredient.
A Cochrane review (Li 2008) of 6 trials with 454 people with Alzheimer's disease found some benefit on general thinking, daily function and behavior compared with placebo, but only one study was of adequate quality and size, and the authors said the evidence was inadequate to make any recommendation. A 2013 meta-analysis (Yang) of 20 trials with 1,823 people found similar benefits but said most trials had a high risk of bias. In a 210-person US trial (Rafii 2011), 200 mcg twice a day did not improve thinking scores at 16 weeks; a higher 400 mcg twice-a-day dose improved them at 11 weeks in a secondary analysis.
The Cochrane review found adverse events were mild and not different from placebo. Because huperzine A works like prescription cholinesterase inhibitors, tell your prescriber if you take medicine for dementia or any other prescription drug before using it.
We could not find a single published half-life or time to peak for huperzine A that applies to a supplement dose, so we do not list one.
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