Supplement analysis backed by scientific evidence · PT · ES · DE · FR

← All supplements
Limited evidenceMen's health

Horny Goat Weed

Horny goat weed (Epimedium) has no credible human trials for erectile dysfunction — the entire premise is in-vitro PDE5 inhibition by icariin that is orders of magnitude weaker than sildenafil. Its only decent randomized data are for bone loss, and this category is a hotspot for products spiked with prescription ED drugs.

What the science says

  • Improves erectile dysfunction Limited evidence

    Icariin does inhibit phosphodiesterase-5 in vitro, but at roughly 80-fold lower potency than sildenafil, and oral bioavailability is poor. There are no adequately designed, placebo-controlled human trials of Epimedium for erectile function using validated instruments such as the IIEF. Every claim here is extrapolated from cell and rodent work.

  • Prevents postmenopausal bone loss Limited evidence

    A 24-month randomized, double-blind, placebo-controlled trial in late postmenopausal women found Epimedium-derived flavonoids (60 mg icariin plus small amounts of daidzein and genistein daily) significantly slowed bone mineral density loss at the femoral neck and lumbar spine versus placebo. This is a single trial of a specific combination product with no fracture endpoints, and it has not been replicated — it does not make Epimedium a bone therapy.

  • Delivers meaningful icariin exposure from standard supplements Limited evidence

    A randomized, double-blind, placebo-controlled trial in postmenopausal women characterizing Epimedium prenylflavonoid pharmacokinetics and effects on bone-specific alkaline phosphatase and the osteoclast adaptor TRAF6 found the extract was tolerated but did not demonstrate the clear bone-turnover changes the mechanism predicts. Absorption of prenylflavonoids is variable and heavily dependent on preparation, so "10% icariin" on a label tells you little about what reaches the bloodstream.

  • Raises testosterone Limited evidence

    No human trial has shown Epimedium raises testosterone. The claim comes from the folk name and from animal studies at doses that do not translate.

Dosage & safety

Studied doseNo effective human dose is established for sexual function. The bone trial used a combination product supplying 60 mg icariin/day for 24 months. Commercial extracts standardized to 10-20% icariin are typically taken at 500-1,000 mg/day, which is a marketing convention rather than a studied dose.
SafetyReported effects include tachycardia, palpitations, dizziness, dry mouth, nosebleeds, and case reports of hypomania and of arrhythmia including AV block; severe hepatotoxicity has been described with Epimedium-containing products. The single largest hazard is adulteration — the FDA has repeatedly issued public notifications for "male enhancement" products, including horny goat weed formulas, found to contain undeclared sildenafil, tadalafil or unapproved analogues. That combination is potentially fatal with nitrates and dangerous with alpha-blockers or in cardiac disease. Epimedium also has phytoestrogenic activity, so avoid it with hormone-sensitive cancers, in pregnancy and while breastfeeding. It may add bleeding risk with anticoagulants. Buy only third-party-tested products, and treat any product that produces a dramatic same-day erectile effect as almost certainly adulterated.

How to take it

TimingNo studied timing exists, and there is no evidence for taking it before sex.
With food?With food to reduce nausea.
Worth knowingIf a product gives you a dramatic same-day erectile effect, assume it contains an undeclared PDE5 drug and stop — that is a repeatedly documented FDA finding, not a theoretical worry.

Interactions

With medications

  • nitrates (glyceryl trinitrate, isosorbide)

    These products are repeatedly found adulterated with undeclared sildenafil or tadalafil, a combination that can cause fatal hypotension with nitrates. do not take any male-enhancement product if you use nitrates

  • alpha-blockers and antihypertensives

    The same undeclared PDE5 inhibitors cause dangerous blood-pressure drops with these drugs. do not combine; buy only third-party-tested products

  • warfarin, DOACs and antiplatelet drugs

    Epimedium may add to bleeding risk. talk to your doctor before combining

Well-established interactions only — this is not a complete list. Always tell your doctor and pharmacist what you take.

Frequently asked questions

Does horny goat weed work for erectile dysfunction?

There are no adequately designed human trials of horny goat weed (Epimedium) for erectile function, so the evidence is limited. The idea rests on lab data showing its icariin inhibits PDE5 at roughly 80-fold lower potency than sildenafil, with poor oral absorption.

Does horny goat weed raise testosterone?

No human trial has shown horny goat weed raises testosterone. The claim comes from its folk name and from animal studies at doses that do not translate to people.

Is horny goat weed safe?

Horny goat weed has been linked to palpitations, dizziness, nosebleeds, arrhythmia and severe liver toxicity. The biggest hazard is adulteration: the FDA has repeatedly found male-enhancement products, including horny goat weed formulas, spiked with undeclared sildenafil or tadalafil.

Can I take horny goat weed with nitrates or blood pressure drugs?

No. Horny goat weed products are repeatedly found to contain hidden PDE5 drugs, which can cause fatal blood-pressure drops with nitrates and dangerous drops with alpha-blockers. If you take nitrates, avoid male-enhancement products altogether.

Scientific references

Related in Men's health