Horny goat weed (Epimedium) is a medicinal plant rich in flavonoids such as icariin. Its extracts are widely taken as supplements, and its name reflects its reputation for sex drive, but the human trials we found tested it for bone loss after menopause.
Also known as: Epimedium, icariin, yin yang huo, barrenwort.
A 24-month bone trial used 60 mg of icariin with 15 mg daidzein and 3 mg genistein a day (Zhang 2007). A 6-week safety trial used 740 mg a day of an Epimedium prenylflavonoid extract (Yong 2021). 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.
What studies show: in a 24-month trial of 100 late-postmenopausal women with low bone density, Epimedium flavonoids kept bone density steady while it fell in the placebo group, without changing estradiol or the lining of the uterus (Zhang 2007). A 6-week trial in 58 postmenopausal women found an Epimedium extract raised a marker of bone building and caused no liver, blood or kidney changes (Yong 2021). Those authors note that, despite wide use, the safety, workings and medical uses of Epimedium extracts in people are unknown.
We did not find a human trial of horny goat weed for sexual function to cite here. In the 6-week trial, icariin itself was below detection in blood; the body converted it to other compounds (Yong 2021).
We could not find a single published half-life or time to peak for horny goat weed that applies to a supplement dose, so we do not list one. Herbal products are mixtures of many plant compounds, so no single figure would describe them. In one trial, icariin itself was not detectable in blood; the main compound found was desmethylicaritin (Yong 2021).
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