Horny goat weed (epimedium): what research found

Before you start

Good to know before you start

What are the horny goat weed side effects?

MSK lists sweating or feeling hot (in high doses), a rapid irregular heartbeat, and changes in energy and mood. It gives no rates and says toxicity and safety evaluations are lacking. A pharmacist-reviewed WebMD page names dry mouth, nausea, upset stomach and vertigo as common and says allergic reactions can be serious. EBSCO's research article calls its safety unknown.

Four individual reports

Four reports, each one person's story, not a rate:

• Rash. A 77-year-old man developed a vasculitic rash after ginkgo and/or horny goat weed remedies; it settled when he stopped.
• Heartbeat. A 66-year-old man with congestive heart failure was hospitalised with chest pain and a new symptomatic arrhythmia; he reported taking epimedium daily for two weeks.
• Muscle spasms. A man aged 33 took epimedium bought online for a month and reached hospital with severe spasms and raised creatine kinase and creatinine; he improved and was told to stop.
• Liver tests. A 53-year-old man with raised liver tests had taken the herb daily for over a year; he improved with supportive care and was advised to avoid it, but other medicines, including atorvastatin, were stopped too.

For the 66-year-old man, EBSCO notes his product might have been adulterated, so it is unclear whether the herb caused his symptoms.

Horny goat weed and the liver

The picture is mixed. The abstract of NIH's LiverTox entry says oral forms have not been linked to raised liver enzymes or clinically apparent liver injury. A 2024 review of one species, Epimedium koreanum, says crude extracts show potential hepatotoxicity and calls for more research.

What the bone trials reported on side effects

The bone meta-analysis reports mostly mild stomach reactions or skin allergies, seen in both groups in the trial that gave counts. One trial recorded some liver values above the normal range (AST in one person, ALP in four) that returned to normal. Only 2 of the 10 trials mentioned adverse reactions.

What are the horny goat weed interactions?

Hidden drugs in some products

Prescription drugs have been found in some products marketed for sexual use, including one named for horny goat weed:

• Recall posted by FDA, 6 May 2025. A company announced a voluntary recall of one lot (250214PRO) of a horny goat weed capsule product sold online, after it was found tainted with undeclared sildenafil and propoxyphenylsildenafil.
• A 2015 lab study of 150 herbal supplements marketed for sexual enhancement found 61% adulterated with PDE-5 inhibitors. Only 31% could be considered true herbal products.

FDA keeps a database of such products. It says they pose a serious health risk and that its list covers only a small fraction of contaminated products. FDA does not approve supplements before sale.

For gummy labels in general, see our buyer's checklist for gummies.

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