Herb & supplement monograph

Horny Goat Weed Drug Interactions, Uses, Effectiveness, Safety & More

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS ·Updated July 2026

What is this page for?

First and foremost: how Horny Goat Weed interacts with medications. The heart of this page is the interaction list — every drug Horny Goat Weed is known to interact with, and how serious each one is.

But these pages have grown well beyond that into a full monograph — what Horny Goat Weed is, what people use it for and how strong the evidence is, its safety and side effects, and answers to the questions we’re asked most — written and reviewed by the clinical staff at HelloPharmacist. It’s educational information from our licensed clinical databases, not medical advice, and we don’t sell or endorse products. Our editorial policy

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Horny Goat Weed Drug Interactions: The Bottom Line

From the HelloPharmacist Editorial Team · Updated July 2026

Based on the available evidence, the overall risk of a clinically significant Horny Goat Weed drug interaction appears low for most people, since nearly all reported concerns come from lab or animal research rather than human studies. Every listed interaction is rated moderate rather than major, and almost all are theoretical, with effects that have not been reported in people.

Interactions deserving the most attention

The interaction with estrogens stands out because human research has shown horny goat weed can raise estrogen levels in some women, which could add to the effects of estrogen-containing medicines. It also deserves caution alongside blood thinners, since lab and animal studies suggest it may reduce clotting, and with blood pressure medications, where a possible pressure-lowering effect could add up. None of these effects has been confirmed in humans, but bleeding and blood pressure are areas where even a small change can matter.

What the rest of the list means

The long list of interacting medications looks alarming, but most entries exist because lab studies suggest horny goat weed may slow enzymes the body uses to clear many common drugs. That is a theoretical concern, and these predicted effects have not been reported in people. A listed interaction does not mean the combination has actually caused harm.

Check your medications against Horny Goat Weed

Based on HelloPharmacist’s Horny Goat Weed interaction data and reviewed under our editorial standards.

Interaction report

Drugs that interact with Horny Goat Weed

965 medications have a known interaction with Horny Goat Weed, graded by severity. Select any drug for the full evidence-based detail.

Don’t want to scroll the list? Just ask.

Tell us the medications you take and we’ll check each one against Horny Goat Weed using our pharmacist-reviewed interaction data.

AI summaries are generated from our Horny Goat Weed interaction data for education only — always confirm with your pharmacist. How we use AI

2,830 drugs

Read The List Like a Pharmacist

What Severity, Likelihood & Evidence Mean

Severity — How Serious It Can Be

Major. Clinically significant; generally best avoided, or used only under direct professional supervision.
Moderate. May need monitoring, a dose adjustment, or separating the times you take each one.
Minor. Generally not clinically significant, but still worth noting and mentioning to your pharmacist.
No known interaction. Checked against our sources with nothing documented — not the same as proven safety.

Likelihood — How Well It’s Documented

Likely. Well-controlled human studies have demonstrated the likely existence of this interaction
Probable. Interaction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
Possible. Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists
Unlikely. Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans.

Where This Data Comes From

Interaction records are evidence-graded and sourced from the Natural Medicines database (TRC Healthcare), the same reference used by pharmacists and hospitals.
Each drug listed above links to the full report for that exact Horny Goat Weed combination — clinical detail, likelihood, evidence level, and citations.
Content is reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

The big picture

The kinds of drugs Horny Goat Weed affects

Every type of medication (drug category) Horny Goat Weed is known to interact with. Open any category for the detail — or search your exact drug in the checker above.

All 6 drug categories Horny Goat Weed interacts with

Anticoagulant/antiplatelet DrugsAntihypertensive DrugsCytochrome P450 1a2 (cyp1a2) SubstratesCytochrome P450 2b6 (cyp2b6) SubstratesCytochrome P450 3a4 (cyp3a4) SubstratesEstrogens

Anticoagulant/Antiplatelet Drugs

Theoretically, horny goat weed might increase the risk of bleeding.
In vitro research and animal research shows that horny goat weed can inhibit platelet aggregation and thrombus formation. This effect has not been reported in humans.

Likelihood Possible Evidence D

Antihypertensive Drugs

Theoretically, horny goat weed might increase the risk of hypotension.
Laboratory research suggests that horny goat weed might have hypotensive effects. This effect has not been reported in humans.

Likelihood Possible Evidence D

Cytochrome P450 1A2 (Cyp1A2) Substrates

Theoretically, horny goat weed might increase the effects and side effects of CYP1A2 substrates.
In vitro, horny goat weed leaf extract inhibits CYP1A2. This effect has not been reported in humans.

Likelihood Possible Evidence D

Cytochrome P450 2B6 (Cyp2B6) Substrates

Theoretically, horny goat weed might increase the effects and side effects of CYP2B6 substrates.
In vitro, horny goat weed leaf extract inhibits CYP2B6. This effect has not been reported in humans.

Likelihood Possible Evidence D

Cytochrome P450 3A4 (Cyp3A4) Substrates

Theoretically, horny goat weed might increase the effects and side effects of CYP3A4 substrates.
In vitro, horny goat weed extract inhibits CYP3A4 and suppresses CYP3A4 mRNA expression. This effect has not been reported in humans.

Likelihood Possible Evidence D

Estrogens

Theoretically, concomitant use of horny goat weed with estrogens might increase their therapeutic and adverse effects.
In vitro evidence suggests that horny goat weed has estrogenic activity. In clinical research, horny goat weed has been shown to increase blood levels of estrogen in some females.

Likelihood Possible Evidence D

Monograph

Horny Goat Weed: Uses, Safety & Side Effects

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS · Reviewed July 2026 ·

The bottom line

Horny goat weed (Epimedium) is a traditional Chinese herb most often marketed for low libido and erectile problems, but solid human evidence for these uses is lacking. While short-term use seems generally tolerated by some people, quality and safety are not well studied, so talk to your pharmacist or doctor before trying it—especially if you have heart problems or take other medicines.

Scientific name: Epimedium grandiflorum
Family: Berberidaceae
Part used: Leaves and aerial parts (sometimes whole herb)
Common forms: Capsules, tablets, powders, tinctures, teas, and combination products

People commonly use it for

Erectile dysfunction
Low libido
Fatigue and low energy
Bone health
Joint and menopausal symptoms
General 'vitality' or performance

Popular and traditional uses — not proof it works. See “Uses & effectiveness” below for the evidence.

Safety at a glance

OverallUse caution

Human safety data is limited; short-term use may be tolerated but quality varies between products.

PregnancyPossibly Unsafe

When used orally. Horny goat weed might have androgenic activity. Theoretically, it might harm a developing fetus; avoid using.

Read the full pregnancy detail

BreastfeedingInsufficient reliable information

Insufficient reliable information available; avoid using.

Read the full breastfeeding detail

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center). Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

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Overview

Horny goat weed comes from plants in the Epimedium genus, a group of flowering herbs native to parts of Asia, especially China, and also found in other regions. The plant has heart-shaped leaves and small, often purple or yellow flowers. It is also called barrenwort or, in traditional Chinese medicine, yin yang huo.

The leaves and above-ground parts have been used for centuries in traditional Chinese medicine. Today it is sold as a dietary supplement in capsules, tablets, powders, teas, and liquid extracts—often promoted for sexual function and energy. It is frequently combined with other herbs in 'male enhancement' or 'vitality' blends.

How it works

The main compounds studied in horny goat weed are flavonoids, especially one called icariin. In laboratory research, icariin appears to act somewhat like a PDE5 inhibitor—the same family of action as some prescription ED drugs—which could in theory improve blood flow.

Other lab and animal studies suggest the herb's flavonoids may have antioxidant and anti-inflammatory effects and might influence bone-forming cells or hormone-related pathways. These mechanisms are mostly based on cell and animal research and do not prove the herb produces the same effects in people.

Effectiveness

Does Horny Goat Weed work?

Here’s what the research actually shows for each use — graded by Natural Medicines and reviewed by Dr. Brian Staiger, PharmD.

Evidence overview · 15 uses evaluated

15 Insufficient evidence

How to read these evidence grades

Natural Medicines’ 7-point scale. We show each rating’s label word-for-word.

1EffectiveStrong, consistent evidence it works.

2Likely EffectiveGood evidence, though not yet conclusive.

3Possibly EffectiveSome evidence suggests a benefit.

4Possibly IneffectiveSome evidence it may not help.

5Likely IneffectiveFairly strong evidence it doesn’t help.

6IneffectiveStrong evidence it doesn’t work.

7Insufficient Reliable Evidence to RateToo little research to say either way.

For Horny Goat Weed, current evidence isn’t strong enough to rate any specific use. The conditions it has been studied for are listed below.

Also studied for 15 conditions — evidence insufficient to rate

Insufficient Reliable Evidence To Rate Bronchitis