Horny Goat Weed
Epimedium
TL;DR
Traditional Chinese herb (Epimedium) marketed for libido and ED. Its flavonoid icariin is a weak PDE5 inhibitor in vitro, but human evidence is essentially absent — no quality RCTs support the marketing claims.
Ideal For
- Few people, given the evidence gap
- Those who understand the lack of human trial data
Avoid If
- Heart conditions or arrhythmia history
- Hormone-sensitive conditions
- Taking nitrates, blood pressure, or blood-thinning medications
Frequently Asked Questions
Overview
Horny goat weed refers to several Epimedium species used in traditional Chinese medicine for fatigue and sexual dysfunction. The active flavonoid icariin inhibits PDE5 — the same enzyme targeted by sildenafil — but roughly 80-fold more weakly in vitro, and oral bioavailability is poor. The critical problem is the evidence base: there are no well-designed human randomized trials demonstrating benefit for erectile function or libido. Most claims trace to animal studies, cell work, and traditional use. Safety data in humans is also sparse; case reports describe tachyarrhythmia and hypomania with high-dose products, and the supply chain is plagued by adulteration with undeclared PDE5 drugs. Given unproven benefit and real product-quality risks, this is a supplement to approach with skepticism.
How It Works
- Icariin weakly inhibits PDE5 in vitro (~80x weaker than sildenafil)
- Preclinical estrogenic and neurotrophic effects, unconfirmed in humans
- Poor oral bioavailability limits achievable tissue concentrations
Benefits & Outcomes
No linked outcomes yet. Research is ongoing.
Supporting Research5 studies
Comprehensive review of the traditional uses and the potential benefits of Epimedium folium
Lin L, Shi Z, Gao Y +2 more
Rigorous human trials of single-herb Epimedium are largely absent.
Pharmacological actions of the bioactive compounds of Epimedium on the male reproductive system: current status and future perspective
Zhang Y, Wang H, Chen L
Icariin acts as a weak phosphodiesterase-5 inhibitor and improves erectile parameters in animal models, but no adequately powered human randomised trials exist.
Epimedium for osteoporosis based on Western and Eastern medicine: a systematic review and meta-analysis
Yang A, Yu C, Lu Q +3 more
Epimedium-based interventions were associated with improved bone mineral density, though most trials were of low methodological quality.
Pharmacological effects and pharmacokinetic properties of icariin, the major bioactive component in Herba Epimedii
Wang S, Ma J, Zeng Y +5 more
Icariin has poor oral bioavailability and extensive first-pass metabolism.
Erectogenic and neurotrophic effects of icariin, a purified extract of horny goat weed (Epimedium spp.) in vitro and in vivo
Shindel AW, Xin ZC, Lin G +7 more
Icariin inhibited PDE-5 with modest potency and improved erectile recovery in the rat model.
Safety Information
Pregnancy & Breastfeeding
Pregnancy: likely_unsafe
Breastfeeding: insufficient_data
Detailed safety information not yet available. Always consult a healthcare provider.
Dosage Guidelines
Dosage Used in Studies
Consult healthcare provider
Forms Compared
Typically standardized to 10–20% icariin; quality varies widely
Traditional preparation; unpredictable icariin content
Medical Disclaimer
The information provided on this website is for educational and informational purposes only and is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition or before starting any supplement regimen.
Individual results may vary. The statements on this website have not been evaluated by the Food and Drug Administration. Products and information are not intended to diagnose, treat, cure, or prevent any disease.