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
What is horny goat weed?
Does it work for erectile function?
What about bone health?
What dose is used?
Is it safe?
Are there adulteration risks?
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.
Health Concerns Addressed
Decreased Sex Drive
Traditional use and animal data only — no quality human trials.
Erectile Dysfunction
No trial of horny goat weed alone in men with ED; the case rests on lab and rat studies of icariin and two small multi-herb trials.
Supporting Research10 studies
Pharmacokinetics of Prenylflavonoids following Oral Ingestion of Standardized Epimedium Extract in Humans
Teo YL, Cheong WF, Cazenave-Gassiot A +4 more
Epimedium prenylflavonoid extracts were well tolerated and no adverse effects were observed
A randomized, double-blind, placebo-controlled crossover study of Cappra® for the treatment of mild or mild to moderate erectile dysfunction in Thai male
Punyawudho B, Puttilerpong C, Wirotsaengthong S +1 more
Cappra(®) is effective and well-tolerated
An Analysis of Popular Online Erectile Dysfunction Supplements
Balasubramanian A, Thirumavalavan N, Srivatsav A +4 more
Ginseng, horny goat weed, L-arginine, and tongkat ali were the most popular ingredients
A systematic review and evidence-based analysis of ingredients in popular male testosterone and erectile dysfunction supplements
Kuchakulla M, Narasimman M, Soni Y +3 more
Horny goat weed, and Yohimbine were most common
Improvement of symptoms of aging in males by a preparation LEOPIN ROYAL containing aged garlic extract and other five of natural medicines - comparison with traditional herbal medicines (Kampo)
Nishimatsu H, Kitamura T, Yamada D +4 more
cuscuta seed and epimedium herb
Comprehensive review of the traditional uses and the potential benefits of Epimedium folium
Cui J, Lin L, Hao F +4 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
Liu SP, Li YF, Zhang D +4 more
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
Shi S, Wang F, Huang Y +4 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
Li C, Li Q, Mei Q +1 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: Not enough evidence to judge
Detailed safety information not yet available. Always consult a healthcare provider.
Dosage Guidelines
Dosage Used in Studies
Consult healthcare provider
Dosing by Goal
| Goal | Dose | Notes |
|---|---|---|
| Typical | 250–1000 mg extract daily (often 10–20% icariin) | No clinically validated human dose exists |
Forms Compared
Capsules/tablets
Typically standardized to 10–20% icariin; quality varies widely
Tea/raw herb
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.