Horny goat weed
No controlled human trial of horny goat weed alone for erectile function, libido or testosterone was located. In 100 postmenopausal women, an icariin-based Epimedium flavonoid blend held bone density steady over 24 months while it fell with placebo. A 6-week trial found no liver, blood or kidney changes. Case reports describe tachyarrhythmia with hypomania and psychosis.
Add to Bio HackChecked 2026-11-09
- Status
- Dietary supplement in the US.
- Also called
- epimedium, Epimedium brevicornum, Epimedium sagittatum, yin yang huo, Herba Epimedii, icariin, rowdy lamb herb, barrenwort
- Taken for
- erectile function, libido, testosterone, sexual performance, bone health
Strong several reviews agree · Moderate one review or consistent trials · Limited one or a few small studies · Untested no study in people, listed with what it rests on
Shown to help1
Reported risks2
- LimitedCase reports: fast heart rhythm, hypomania and new psychosis after horny goat weed use.How often is not known
- LimitedCase reports: a vasculitic rash attributed to ginkgo, horny goat weed or both, taken together.How often is not known
What people take it for, and what was found
Shown to help1
Bone density after menopause
Shown to keep bone density steady over 2 years in postmenopausal women with low bone density, on a blend with soy isoflavones, while it fell on placebo.
The numbers and sources
- Effect
- In 100 late postmenopausal women with low bone density, a daily blend of 60 mg icariin, 15 mg daidzein and 3 mg genistein held bone density steady over 24 months. With placebo, lumbar spine density fell 2.4% and femoral neck density 1.8%. The groups differed at the lumbar spine at 12 and 24 months and at the femoral neck at 24 months. Both groups took 300 mg of calcium a day, and endometrial thickness showed no detectable hyperplasia [1]. A meta-analysis of 12 RCTs with 1,017 patients found higher bone density when Epimedium was added to conventional osteoporosis drugs (p = 0.03) or used in place of them (p = 0.009) [2]. In 58 postmenopausal women, 740 mg a day of Epimedium prenylflavonoids for 6 weeks raised the bone formation marker BSAP [3]. A 2025 meta-analysis of 10 RCTs (890 patients with primary osteoporosis) found higher lumbar spine bone density with Epimedium as an add-on or alternative to conventional drugs (SMD 1.15, 95% CI 0.61 to 1.70) [4].
- Population
- 100 postmenopausal women [1]; patients with osteoporosis in 12 RCTs [2] and 10 RCTs [4]; healthy postmenopausal women [3].
- Sources
- [1], [2], [3], [4]
- Caveats
- The blend in [1] also contained soy isoflavones. The trials in [2] and [4] compared Epimedium with conventional drugs, not placebo, and the abstract of [2] gives p-values without effect sizes. Review [4] searched Chinese databases.
Claimed, not studied in people3
Erectile function
Not studied in people. Used traditionally for impotence, its extract and icariin block the PDE5 enzyme in the lab, and icariin protected penile tissue in diabetic rats.
No study in people. This rests on lab studies, animal studies, documented traditional use.
The numbers and sources
- Effect
- In a screen of plant extracts traditionally used for male impotence, Epimedium brevicornum extract inhibited human PDE5, the enzyme sildenafil blocks, by 80% at 50 µg/mL, and icariin had an IC50 of 5.9 µM, about 80 times weaker than sildenafil [9]. In diabetic rats, 3 months of icariin partially preserved the smooth muscle and blood vessel lining of the penis that diabetes damaged [10].
- Population
- Human recombinant enzyme in the lab [9]. Diabetic Sprague-Dawley rats [10].
- Sources
- [9], [10]
- Caveats
- Lab enzyme activity and rat tissue do not show an effect on erections in people. No controlled trial in men was located.
Libido
Not studied in people. Male mice given icariin for 21 days mated sooner and more often than untreated mice.
No study in people. This rests on animal studies, documented traditional use.
The numbers and sources
- Effect
- In 48 male mice, 21 days of icariin shortened the time to mounting and ejaculation and raised the number of both compared with controls, along with higher serum testosterone, nitric oxide and brain dopamine (all p < 0.05) [11]. The plant is among extracts traditionally used for male impotence [9].
- Population
- Male CD1 mice [11].
- Sources
- [11], [9]
- Caveats
- Mating behavior in mice is not human desire. No study of libido in people was located.
Testosterone
Not studied in people. Icariin raised serum testosterone in male mice and increased testosterone production in mouse testis cells.
No study in people. This rests on animal studies, lab studies.
The numbers and sources
- Effect
- Male mice given icariin for 21 days had higher serum testosterone than controls (p < 0.001) [11]. In mouse Leydig cells, the testosterone-producing cells of the testis, icariin raised the enzymes for testosterone synthesis through an estrogen receptor pathway, and it reversed the fall in those enzymes caused by a phthalate in live mice [12].
- Population
- Male mice and mouse Leydig cells [11][12].
- Sources
- [11], [12]
- Caveats
- No study measured testosterone in people taking horny goat weed or icariin. Animal and cell findings do not show the effect of a supplement in men.
Doses studied
The bone trial used 60 mg of icariin with 15 mg of daidzein and 3 mg of genistein a day for 24 months [1]. The safety trial used 740 mg a day of an Epimedium prenylflavonoid extract for 6 weeks [3]. No dose data for sexual function were located.
Risks
Reported risks2
Heart rhythm and psychiatric case reports
Case reports: fast heart rhythm, hypomania and new psychosis after horny goat weed use.
The numbers and sources
- How common
- How often is not known: the sources give no rate.
- Effect
- A published report describes tachyarrhythmia and hypomania with horny goat weed [5]. A 2026 report describes new-onset psychosis in a person with Parkinson's disease after horny goat weed use [6]. A review of sexual enhancement products sold online found horny goat weed reported with adverse events and psychological symptoms such as mood changes, anxiety and hallucinations [7].
- Population
- Case reports [5][6]; review of 203 websites and the medical literature [7].
- Sources
- [5], [6], [7]
- Caveats
- Abstracts were not available for [5] and [6]. Case reports cannot establish cause.
Rash
Case reports: a vasculitic rash attributed to ginkgo, horny goat weed or both, taken together.
Checked, no increase found1
Safety in controlled trials
Small trials in postmenopausal women found no significant adverse symptoms or lab changes. Osteoporosis trials reported mild gut or skin reactions.
The numbers and sources
- How common
- How often is not known: the sources give no rate.
- Effect
- In 58 postmenopausal women over 6 weeks, Epimedium prenylflavonoids caused no significant adverse symptoms and no changes in liver, blood or kidney tests [3]. Over 24 months, the icariin blend showed no detectable endometrial hyperplasia [1]. In 10 osteoporosis RCTs, adverse reactions were described as low, mainly mild gastrointestinal reactions or skin allergies [4].
- Population
- Postmenopausal women [1][3]; patients with osteoporosis [4].
- Sources
- [1], [3], [4]
- Caveats
- Trials in women for bone outcomes. No safety data in men using it for sexual function were located.
Sources
- Zhang G, Qin L, Shi Y. Epimedium-Derived Phytoestrogen Flavonoids Exert Beneficial Effect on Preventing Bone Loss in Late Postmenopausal Women: A 24-Month Randomized, Double-Blind and Placebo-Controlled Trial. Journal of Bone and Mineral Research. 2007. https://doi.org/10.1359/jbmr.070405
- Shi S, Wang F, Huang Y, et al. Epimedium for Osteoporosis Based on Western and Eastern Medicine: An Updated Systematic Review and Meta-Analysis. Frontiers in Pharmacology. 2022. https://doi.org/10.3389/fphar.2022.782096
- Yong EL, Cheong WF, Huang Z, et al. Randomized, double-blind, placebo-controlled trial to examine the safety, pharmacokinetics and effects of Epimedium prenylflavonoids, on bone specific alkaline phosphatase and the osteoclast adaptor protein TRAF6 in post-menopausal women. Phytomedicine. 2021. https://doi.org/10.1016/j.phymed.2021.153680
- Zhang XQ, Hua ZH, Huang CJ, et al. The efficacy and safety of Epimedium in the treatment of primary osteoporosis: a systematic review and meta-analysis. Frontiers in Medicine. 2025. https://doi.org/10.3389/fmed.2025.1675160
- Partin JF, Pushkin YR. Tachyarrhythmia and Hypomania With Horny Goat Weed. Psychosomatics. 2004. https://doi.org/10.1176/appi.psy.45.6.536
- Deliz JR, Manoocheri K, Larson DN, et al. New-Onset Psychosis in a Person with Parkinson's Disease after "Horny Goat Weed" Use. Movement Disorders Clinical Practice. 2026. https://doi.org/10.1002/mdc3.70350
- Corazza O, Martinotti G, Santacroce R, et al. Sexual Enhancement Products for Sale Online: Raising Awareness of the Psychoactive Effects of Yohimbine, Maca, Horny Goat Weed, and Ginkgo biloba. BioMed Research International. 2014. https://doi.org/10.1155/2014/841798
- Metz D, Weston P, Barker D. Case report of vasculitic rash induced by Ginkgo biloba and/or Horny Goat Weed. BMJ Case Reports. 2009. https://doi.org/10.1136/bcr.07.2008.0399
- Dell'Agli M, Galli GV, Dal Cero E, et al. Potent inhibition of human phosphodiesterase-5 by icariin derivatives. Journal of Natural Products. 2008. https://doi.org/10.1021/np800049y
- Liu T, Xin H, Li WR, et al. Effects of icariin on improving erectile function in streptozotocin-induced diabetic rats. The Journal of Sexual Medicine. 2011. https://doi.org/10.1111/j.1743-6109.2011.02421.x
- Ding J, Tang Y, Tang Z, et al. Icariin improves the sexual function of male mice through the PI3K/AKT/eNOS/NO signalling pathway. Andrologia. 2018. https://doi.org/10.1111/and.12802
- Sun J, Xu W, Zheng S, et al. Icariin promotes mouse Leydig cell testosterone synthesis via the Esr1/Src/Akt/Creb/Sf-1 pathway. Toxicology and Applied Pharmacology. 2022. https://doi.org/10.1016/j.taap.2022.115969