THERAPIES & TRADITIONS · GUIDE
Epimedium (Yin Yang Huo, Horny Goat Weed) in Chinese Medicine
Epimedium (Yin Yang Huo, horny goat weed) is a Chinese kidney-yang tonic marketed for sexual function; here is the evidence, what tainted products are, and liver and quality cautions.
Content last updated . This page has not been medically reviewed.
Back to Traditional Chinese MedicineWhat it is
Epimedium is a group of plants known as Yin Yang Huo in Chinese and "horny goat weed" in supplement marketing. A systematic review of one species, Epimedium koreanum, describes it as a well-known "kidney tonic". [1] Its best-known compound is icariin, a flavonoid. [2]Traditional use
The review above lists traditional uses for renal "yang deficiency", impotence, spermatorrhea, weak tendons and bones, rheumatic pain and numbness. [1] "Kidney yang" is a traditional framework term, not the organ; see Qi, Yin and Yang, Five Phases and Meridians as Traditional Concepts. These are traditional uses, not tested outcomes.What research shows
Sexual function: insufficient evidence in people. A 2022 narrative review says icariin and some derivatives inhibit the enzyme PDE5 in lab studies and may support erectile function in animals, and concludes that more high-quality, large clinical research is needed. [2] A urologist's review of top-selling men's sexual-health supplements, which included horny goat weed, found that the medical literature on the efficacy of these ingredients is generally of low quality. [3] In short, a lab mechanism is not proof that a product works. For the broader topic see Erectile Dysfunction.Bone after menopause: promising but limited. A 24-month randomized, placebo-controlled trial in 100 healthy late-postmenopausal women (85 finished) tested Epimedium-derived flavonoids (icariin, daidzein, genistein) with calcium. Bone density was maintained in the treatment group while it declined in the placebo group, with no detectable change in endometrial thickness. [4] It is a single trial of one specific extract, in one population, and does not apply to other products. A separate 6-week placebo-controlled safety trial in 58 postmenopausal women found no significant adverse symptoms or changes in liver, blood or kidney tests. [5] That is short-term and in healthy women.
Other uses: Proper evidence not found for energy, fertility, arthritis or cancer in people; we searched PubMed for clinical trials of Epimedium and icariin and found the above plus laboratory reviews.
Where to read more
See Chinese Herbal Medicine, Tribulus (Bai Ji Li): Traditional Use vs Supplement Claims and How Supplements Are Regulated.Frequently asked questions
Is horny goat weed the same as Yin Yang Huo?
Yes. Yin Yang Huo is the Chinese name for Epimedium, and "horny goat weed" is the supplement name. [1]
Does horny goat weed work for erectile dysfunction?
There is insufficient evidence in people. Lab studies suggest PDE5 inhibition by icariin, but reviewers call for better clinical research. [2]
Can sexual-enhancement supplements contain hidden drugs?
Yes. FDA reports undeclared sildenafil and tadalafil in some, with a danger for people on nitrates. [6]
Can Epimedium harm the liver?
A review states crude extracts show potential hepatotoxicity. [1] A short 6-week trial found no liver changes in healthy postmenopausal women. [5]
Does it help bones?
One 24-month trial of an Epimedium flavonoid extract with calcium maintained bone density in postmenopausal women compared with placebo. [4] More research is needed.
More details: evidence, limits and cautions
The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.
Safety and quality
- Hidden drugs in "male enhancement" products. The US FDA says products promoted for sexual enhancement have been found to contain undeclared sildenafil and tadalafil (the active drugs in Viagra and Cialis), which may interact with nitrates such as nitroglycerin and may lower blood pressure to dangerous levels. FDA also says it is unable to test and identify all products marketed as dietary supplements with hidden ingredients. [6] The FDA page we read does not name Epimedium; the point is that an "all natural" product in this category cannot be assumed to contain only what the label says. See Unsafe Products and Warnings.
- Liver. A review of E. koreanum states that crude extracts show potential hepatotoxicity and that more study is needed. [1] See Liver Safety and Supplements.
- Blends. Sexual-health products often combine many ingredients, up to 33 in one formulation the urologists' review identified. [3] That makes the effect of any single herb impossible to separate.
- Pregnancy, breastfeeding, children and interactions: the sources we read gave no data, so treat them as unknown. Because some Epimedium flavonoids are described as phytoestrogens, ask a clinician before use if you have a hormone-sensitive condition. [4]
When to seek care
References
- A systematic review of traditional uses, phytochemistry, pharmacology and toxicity of Epimedium koreanum Nakai. J Ethnopharmacol 2024. PubMed 37544344. Read 2026-10-22.
- Deciphering the myth of icariin and synthetic derivatives in improving erectile function: a narrative review. Transl Androl Urol 2022. PubMed 35958901. Read 2026-10-22.
- A urologist's guide to ingredients found in top-selling nutraceuticals for men's sexual health. J Sex Med 2015. PubMed 26531010. Read 2026-10-22.
- Epimedium-derived phytoestrogen flavonoids and bone loss in late postmenopausal women: a 24-month randomized, double-blind, placebo-controlled trial. J Bone Miner Res 2007. PubMed 17419678. Read 2026-10-22.
- Randomized, double-blind, placebo-controlled trial of Epimedium prenylflavonoids in post-menopausal women. Phytomedicine 2021. PubMed 34352588. Read 2026-10-22.
- US FDA. X10 Natural Enhancement Supplement may be harmful due to hidden drug ingredients (content current as of 05/29/2026). Read 2026-10-22.