What is horny goat weed? Does it work?

Horny goat weed is perhaps the most literally named supplement of all time—Chinese farmers noticed that goats seen eating the herb later seemed to be unusually “in the mood.” Enough supplement manufacturers believe in its efficacy that it's included in dozens of supplements that claim to improve your libido and sexual performance. But does that mean you should be adding horny goat weed pills into your daily repertoire? Let’s look at what the research has to say. 

Horny goat weed is a traditional Chinese medicinal herb known as epimedium or yin yang huo. It comes from a flowering shrub native to China and has been used in traditional Chinese medicine to treat fatigue and low libido for thousands of years. 

Today, horny goat weed is most commonly taken as an aphrodisiac. It's claimed to boost sex drive and improve the quality of erections, among other effects. Horny goat weed is available as a tablet, capsule, tea, or powder, either on its own or as part of other supplement formulations. (It might be listed on a label as Epimedium, Epimedium sagittatum, Epimedium grandiflorum, or Epimedium koreanum). 

The active ingredient in horny goat weed is icariin, a compound that’s been studied in animals for a wide range of potential benefits. While we don’t know that it has the same effects in humans, horny goat weed has shown anti-inflammatory and antioxidant effects, as well as heart protection and better erections in animal studies (Fang, 2017; Yang, 2021). 

But does horny goat weed have these effects in humans? Let’s take a look. 

A 2010 study found that icariin seemed to benefit rats who had damaged blood vessels. Those fed an icariin supplement were better able to synthesize nitric oxide in penile tissue (an essential part of getting an erection) than those fed a placebo  (Shindel, 2010).

In another study, researchers found that older rats fed an icariin extract for ten days had more frequent ejaculations and a shorter latency period between ejaculation (Makarova, 2007).

Studies have found that icariin inhibits PDE5—the same mechanism of drugs like Viagra (generic name sildenafil) or Cialis (generic name tadalafil) (though icariin is much less potent than these prescription drugs) (Xin, 2003). 

Unfortunately, these studies on the effects of icariin are mostly suggestive; they’ve been conducted on animals and in test tubes. Horny goat weed may not work the same way in the human body. There haven’t been any studies on horny goat weed’s effect on ED in humans.

Horny goat weed has also been touted as a potential treatment for the following medical conditions:

• High blood pressure (Anand Ganapathy, 2021)

• Atherosclerosis (Fang, 2017)

• Low libido (Anand Ganapathy, 2021)

• Autoimmune conditions (Pu, 2021)

• Osteoporosis—One study found that taking horny goat weed for 24 months, plus calcium supplements, decreased bone loss in postmenopausal women better than taking calcium alone (Zhang, 2007).

• Asthma (Hu, 2019)

• Brain injury (Liu, 2011)

• Menopausal symptoms—Horny goat weed is believed to act similarly to estrogen. A 2008 study found that postmenopausal women who took horny goat weed extract for six months had lower cholesterol and higher estrogen levels than those who didn’t (Yan, 2008)

Although some studies have been done, the National Institutes of Health (NIH) says that there’s insufficient evidence that horny goat weed is effective for any of the above conditions, including ED. More research is needed (MedlinePlus, 2021).  

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According to the NIH, horny goat weed is probably safe when taken by mouth in appropriate doses. Side effects such as upset stomach, dry mouth, nosebleeds, dizziness, and rapid heartbeat have been reported (MedlinePlus, 2021). But horny goat weed could have adverse effects when taken with other medications, supplements, or health conditions.

Don’t take horny goat weed if you have a bleeding problem or are scheduled to have surgery; it may affect your blood’s clotting ability. Horny goat weed can also change hormone levels, so you shouldn’t take it if you have a hormone-sensitive cancer (MedlinePlus, 2021).

Don’t take horny goat weed if you’re on certain medications, including (MedlinePlus, 2021): 

• Estrogens

• Drugs that lower blood pressure

• Blood thinners

Let your healthcare provider know about any dietary supplements and medications you’re taking.

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How we reviewed this article

Every article on Health Guide goes through rigorous fact-checking by our team of medical reviewers. Our reviewers are trained medical professionals who ensure each article contains the most up-to-date information, and that medical details have been correctly interpreted by the writer.

Current version

March 17, 2022

Written by

Michael Martin

Fact checked by

Chimene Richa, MD

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About the medical reviewer

Chimene Richa, MD

Dr. Richa is a board-certified Ophthalmologist and medical writer for Ro.