Horny Goat Weed at 8 mg of a 10:1 Extract: What Is Known About Epimedium in Men, and What Is Not

By AlphaSteel Team · Last updated September 26, 2026 · 10 min read · Ingredient row

The horny goat weed row on the panel

The last row of the AlphaSteel Supplement Facts panel reads “Horny Goat Weed (Epimedium sagittatum)”, and beneath it, in smaller type, “From 10:1 extract, equivalent to approximately 80 mg of dry Horny Goat Weed powder”. The amount column says 8 mg. Of the seven actives, this is the smallest by weight: five rows print 20 mg, tongkat ali prints 10 mg, and horny goat weed prints 8.

The two numbers on the row are different kinds of number, and it is easy to read them as one. The 8 mg is the weight of extract in a two-capsule serving. The 80 mg is the weight of dried herb that the label says went into making that extract, ten times as much, because the ratio is 10:1. Only the first can be set beside a study’s dose, for the reasons the post on the tongkat ali ratio gives at length, and the rest of this post uses it.

Horny goat weed is also the ingredient on this panel that carries the most reputation and the least clinical evidence. The name does the marketing, and the research is more modest than the name.

One name, many plants

‘Horny goat weed’ is a common name for members of the genus Epimedium. A review of the genus counts about 52 species and more than 260 compounds isolated from them, with the prenylated flavonoids as the major constituents and the chemical markers used to tell species apart. It lists a long run of common names, from barrenwort and bishop’s hat to yin yang huo, and describes the genus as used in traditional Chinese medicine for, among other things, sexual dysfunction and osteoporosis (Ma 2011).

Which species is in the capsule therefore matters, and the AlphaSteel panel does name one: Epimedium sagittatum. That is more than a bare ‘horny goat weed’, and it is the same species used in a human trial discussed below. Identifying a species is harder than it sounds. One research group that set out to standardise an Epimedium extract wrote that the plant is not cultivated, so taxonomically identified samples had to be sourced, and the species had to be authenticated by phylogenetic, chemical and bioresponse profiling (Yong 2007). The label cannot show you that work. It can only name the species and ask you to trust the supplier.

That same paper made a point the marketing leaves out. Despite the plant’s colloquial name and the internet advertising of it as a herbal ‘Viagra’ for men, the authors found that Epimedium extracts are strongly oestrogenic in their tests, because of prenylflavone phytoestrogens. It is a reminder that a plant with one reputation can have a different measured profile, and that the reputation is not evidence.

Icariin, the compound everyone quotes

Almost every claim about horny goat weed goes through one compound, icariin, a prenylated flavonoid. The best-known laboratory paper screened plant extracts traditionally used for male impotence against human phosphodiesterase-5, the enzyme that sildenafil and similar medicines block. Of the extracts tested, only one from Epimedium brevicornum was active, at 80 per cent inhibition at 50 micrograms per millilitre, and its active compound icariin had an IC50 of 5.9 micromolar. A chemically modified derivative was 80 times more potent, close to sildenafil (Dell’Agli 2008).

Read that sentence twice before repeating it, because it is often quoted as if it said something else. The derivative, not icariin, matched sildenafil. Icariin itself was 80 times weaker than that derivative, and the finding is an enzyme assay in a dish, on a different Epimedium species from the one on the AlphaSteel panel. It gives a reason to take the plant seriously and to ask questions about medicines that act on the same enzyme. It does not show that a capsule does anything of the kind.

Animal work goes a step further. In rats with an injury to the cavernous nerve, four weeks of daily icariin by gavage at 1, 5 and 10 mg per kilogram the group given the low dose showed higher erectile pressure responses than controls, and icariin also encouraged nerve outgrowth in cultured ganglia (Shindel 2010). A narrative review of icariin and erectile function pulled that and related work together and concluded that icariin and some derivatives could be a potential treatment, and that more high-quality clinical and basic research was needed (Niu 2022). Rats given milligrams per kilogram are a long way from a man taking 8 mg, and the review says as much by asking for clinical work.

What reaches the blood of men who take it

Absorption is the step the enthusiastic accounts skip, and it has been measured in men. Thirty healthy men each received a single oral dose of 370, 740 or 1,110 mg of a standardised Epimedium prenylflavonoid extract, or placebo, in a randomised trial, and blood was sampled over 48 hours. The extract was well tolerated and no adverse effects were seen. The main compounds that appeared in serum were icariside II, peaking at about four hours, and desmethylicaritin, which peaked at about 24 hours. Icariin, icariside I and icaritin were below the limit of detection (Teo 2019).

That result fits with the review of icariin above, which reports that 91.2 per cent of icariin is converted to icariside II by gut bacteria after it is swallowed (Niu 2022). Put together, the picture is that the compound in the laboratory papers, icariin, is largely not the compound in the bloodstream. What circulates is a set of metabolites, and their behaviour was studied here for bone and safety, not for men’s sexual function; the authors framed the work around osteoporosis prevention.

This does not mean horny goat weed does nothing. It means the neat story, plant to icariin to enzyme to effect, skips steps that have not been shown in people.

The human studies that measured something

The human trials of Epimedium that exist measured other things. The one that used the same species as the label is a small crossover trial in 29 men with Gulf War illness, testing three botanicals in turn, one of which was Epimedium sagittatum as a 20 per cent icariin extract at 500 mg and then 1,000 mg a day (100 and 200 mg of icariin), for 30 days at each dose. Epimedium did not reduce symptom severity at either dose. The authors called their results preliminary and the sample small. Participants taking antihypertensive medication were not allowed to take the Epimedium, which is worth noticing (Younger 2021).

A longer trial looked at bone. One hundred late postmenopausal women were given a daily combination of 60 mg icariin, 15 mg daidzein and 3 mg genistein from Epimedium, or placebo, for 24 months, with calcium for all. Bone density was maintained on the treatment and fell on placebo, and serum oestradiol and endometrial thickness did not change (Zhang 2007). That is a different plant species, sex and outcome from anything on the AlphaSteel label, and it belongs here only because it shows how long some people have taken Epimedium flavonoids under observation.

What this desk did not find is a randomised trial of Epimedium or icariin on sexual function in men. It searched PubMed on 26 September 2026 with terms for Epimedium, icariin, erectile dysfunction and men, and the results were laboratory papers, reviews and the studies above. A search is not proof of absence, and a reader who finds a trial should tell us. Until then the honest summary is that the men’s-function case for horny goat weed rests on laboratory and animal work.

The 8 mg beside the amounts studied

Amounts are taken from the abstracts and, for Younger 2021, the methods section of the open-access paper. Multiples are this desk’s arithmetic: the study amount divided by 8 mg, rounded. The Younger paper’s discussion section quotes 1,000 and 2,000 mg a day where its methods say 500 and 1,000 mg; this post uses the methods figures, and if the larger ones are right the multiples double.

On the like-for-like measure of extract weight, the label amount is between one part in 46 and one part in 139 of the doses in the two men’s studies. Read the 80 mg on the label as a dry-herb equivalent and the gap looks smaller, but that is the wrong comparison, since the trials dosed extract.

It is possible to overstate the point in the other direction. The trial extracts were characterised by their own standardisation, one at 20 per cent icariin, and the label does not print a standardisation figure. If the extract in the capsule were as rich in icariin as that one, which the panel does not say, 8 mg of it would carry about 1.6 mg of icariin, against 100 to 200 mg in the trial. If it were less rich, the figure would be lower. In neither case can the label be shown to deliver a trial-scale amount, and this website does not claim that it does.

Where this leaves the row

Horny goat weed is a real plant with a real chemistry and a long traditional record. In the laboratory its compound icariin inhibits an enzyme that men’s medicines target. In men, the compound largely does not arrive in the blood as icariin, and no trial this desk could find has tested it for the purpose its name suggests. At 8 mg, the row on this panel is a small share of a seven-ingredient formula, whose label makes three support statements and no claim about erections.

That last point matters for how to read the label. AlphaSteel is sold for energy, male vitality and confidence with the usual dietary-supplement wording, and no published trial of it as a finished product has been found. The horny goat weed row is one of seven, and this post says nothing about how the seven behave together, because nobody has published that.

The interaction question is separate, and it is real enough that the label’s caution and the interaction checklist should be read before the first capsule by anyone taking a prescription for blood pressure, heart rhythm or erectile function, or a nitrate. Both the laboratory finding above and the exclusion of blood-pressure medicine users from the Epimedium arm of the trial point the same way. This post does not repeat the checklist, and it is not a substitute for asking a prescriber.

Questions to put to any horny goat weed label

• Which species? The genus has about 52. The AlphaSteel panel names Epimedium sagittatum, which is the right kind of answer.
• Which part, and how concentrated? The panel prints a 10:1 ratio and a dry-herb equivalent, and no icariin percentage. A ratio describes the recipe; a marker figure describes the content.
• Compare extract with extract. The 8 mg is what to set beside a study’s dose, not the 80 mg.
• What was actually measured? Enzyme assays, rats, absorption in healthy men and symptom scores in men with another condition are four different things, and none of them is a trial of the label claim.
• Who should ask first? Anyone on a prescription, for the reasons above. The side effects and safety page and the label caution say the same.

If you came to this post to find out whether the horny goat weed on the AlphaSteel label is a reason to buy, the fair answer is that it is a reason to read the label closely, which is what the rest of this website is for. The how to take it page sets out the routine, and the 60-day window is there so that your own experience can decide.