Horny Goat Weed

Supplements · Cognitive & Vitality Herbs · Supplement, Typed Supps

A traditional herb sold for libido — but there’s barely any real human research behind it.

Stage by stage

Intake (Extract capsule): Its main active compound, icariin, is absorbed in the small intestine.
Small intestine (Absorbed): Absorbed alongside other plant compounds.
Bloodstream (Circulates): Circulates throughout the body.
Blood vessels (Studied mechanism): Studied in lab settings for effects on blood vessel relaxation, similar in category to some erectile dysfunction medications, though human evidence is much thinner.

What the evidence supports

Improving erectile function or libido in humans — insufficient evidence. The active compound icariin is a weak PDE5 inhibitor in test-tube and rodent work, but there are essentially no adequately sized human trials, so the popular claim rests on mechanism rather than clinical evidence.
Supporting bone density after the menopause — limited evidence. A few small trials of icariin-containing preparations report modest effects on bone markers, but the evidence is preliminary and not specific to the products sold as horny goat weed.

Typical dose

No reliable human-trial dose has been established; products vary widely in icariin content

Upper limit: No established UL

Timing

With food, standard dosing.

Time to effect

Weeks: Any reported effect in studies.

Medication interactions

Nitrates (e.g. nitroglycerin): Because icariin has PDE5 activity — and some products are illegally spiked with sildenafil analogues — combining with nitrates risks a dangerous drop in blood pressure. (high)
Anticoagulants and antiplatelet drugs: May add to bleeding risk; effects on clotting time have been reported. (moderate)

Common myth

“Horny goat weed works like prescription medication for the same purpose.” In reality: Its supporting evidence is mostly from lab and animal studies — robust human clinical trials are notably lacking compared to actual prescription options.