What Is Icariin? How to Read the Label.

The short answer: Icariin is a flavonoid, a type of plant compound, made by Epimedium, the plant group better known as horny goat weed. Makers often measure it to standardize Epimedium extracts. Our Horny Goat Weed & Maca Capsules list 1,000 mg of Epimedium extract per 2-capsule serving, and 100 mg of that is icariins, so the extract is 10% icariins. A percentage tells you concentration. It can't tell you how well a product works.

Key takeaways

• Icariin is a flavonol glycoside, meaning a plant flavonoid with sugar groups attached, and NIH's PubChem database traces it to several Epimedium species.
• An icariin percentage is simple division: milligrams of icariin over milligrams of extract, so 100 mg in 1,000 mg works out to 10%.
• The same 100 mg of icariin can come from 1,000 mg of a 10% extract or about 167 mg of a 60% one, so compare icariin milligrams, not extract milligrams.
• The federal sources we read give icariin neither a daily amount nor an upper limit, so the directions printed on a bottle are the only dosing guide you'll get.

Our stake, up front: Betterly sells Epimedium formulas, and only one of them prints an icariin number. That label and one with no icariin line are the worked examples below, our own gaps included.

What is icariin, and where does it come from?

Icariin is a flavonol glycoside, a flavonoid with two sugar groups attached, made by plants in the Epimedium genus, the herbs sold as horny goat weed.

Flavonoids are pigment-like compounds found all through the plant world, and flavonols are one branch of that family. NIH's PubChem entry for icariin says it comes from several Epimedium species and is thought to be the main active ingredient of Herba Epimedii, the traditional Chinese herb known as yinyanghuo.

Note the hedge in "thought to be." LiverTox, the NIH reference that tracks liver effects of drugs and supplements, puts the number of chemical constituents identified in the plant above 200. Its horny goat weed record lists icariin next to two relatives, icaritin and epimedin, as flavonoids believed to be active.

So "icariin" on a bottle means one measured compound, not the whole herb. Our label names the species, Epimedium sagittatum, and the "aerial" parts, meaning the leaves and stems above ground.

What does "standardized to icariin" mean on a supplement label?

"Standardized to icariin" means the maker measured icariin in each batch of Epimedium extract and adjusted batches so the stated amount stays consistent.

The NIH Office of Dietary Supplements (ODS) lays this out in its botanical supplements background sheet. Makers choose particular chemicals, known as markers, then measure them and adjust each batch to match. Nothing in U.S. law makes a maker do this, ODS points out, and the word has no legal definition here. In practice, "standardized" is a promise about sameness. It isn't a grade.

In a perfect world, the measured chemical would also be the one that acts in your body. For most herbs, ODS explains, that chemical hasn't been identified. For Epimedium, that makes icariin a sensible marker, not a proven one.

Under 21 CFR 101.36, the federal rule behind Supplement Facts panels, a maker may list a constituent such as icariin under its ingredient with its own per-serving weight. Because that's optional, plenty of Epimedium labels leave it off. Ours prints it in parentheses beneath the extract's name. The same rule has an extract with its solvent removed listed at its dried weight, which makes our 1,000 mg a weight of extract powder, not raw leaves or pure icariin.

The math: 100 mg of icariins divided by 1,000 mg of extract is 10%. One quirk: our panel says "icariins," plural, and doesn't define the word or name the test behind it, so we can't break it down further.

How do 10%, 20%, 40%, 60% and 98% icariin extracts compare?

Icariin extracts labeled 10% to 98% differ in how much icariin each milligram carries, so a 60% extract holds six times the icariin per milligram of a 10% one.

Online, you'll find Epimedium extracts sold at 20%, 40% and 60%, and icariin powders labeled 98%. Here's each figure in milligrams:

A higher percentage doesn't change what icariin is, only how much of it sits in each milligram and how much of the rest of the plant comes along.

ODS notes that a single chemical can be isolated from a botanical and sold as a supplement, and a 98% powder comes close to that. At our 10% end, nine-tenths of the extract is something other than icariin, and our panel doesn't say what.

No federal source we read compares these grades in people, so we don't rank them.

From our shop: Horny Goat Weed & Maca Capsules — 1,000 mg of Epimedium sagittatum extract per 2-capsule serving, with 100 mg of icariins stated on the extract's own row, which works out to a 10% extract.

What can't an icariin percentage tell you?

An icariin percentage can't tell you whether a product works, how good it is, what fills the rest of the extract, or how icariin was measured.

• It can't show that a product works. LiverTox says effects reported for Epimedium extracts in people haven't been proven in rigorous prospective controlled trials.
• It can't vouch for quality, since ODS warns that "standardized" on a label is no guarantee of a high-quality product.
• It can't name the rest of the extract. On our label, that's 900 mg per serving.
• It can't show how icariin was measured. Supplement Facts panels skip the test method, ours included.

How much icariin is in a serving, and is there a set dosage?

No federal source we read sets an icariin dosage. Betterly's Horny Goat Weed & Maca Capsules supply 100 mg of icariins per 2-capsule serving, about 50 mg per capsule.

LiverTox describes horny goat weed tablets and capsules of 250 or 500 mg, usually once a day, without saying how much icariin they hold. LiverTox sets no upper limit for the herb or for icariin, and no other federal page we checked does either.

Each of our capsules works out to 500 mg of extract. The same capsule at other grades would hold:

• 50 mg of icariin at 10%
• 100 mg at 20%
• 300 mg at 60%
• 490 mg at 98%

Two identical-looking capsules can differ sixfold between the 10% and 60% grades. Never take extra capsules to match another product's icariin, or go past a label's suggested use.

Some labels don't allow the math at all. Our Tribulus, Zinc & Magnesium Capsules carry 50 mg of horny goat weed (Epimedium sagittatum, aerial) per 3-capsule serving. The row doesn't say "extract" and gives no icariin figure, so any icariin number for it would be a guess.

Only the top row answers the icariin question outright. For the bottom row, our guide to how a proprietary blend hides amounts shows what ingredient order can still tell you.

What do the 1 mg ingredients on our label add?

Our Horny Goat Weed & Maca label's 1 mg longjack and polypody extracts are too little to judge from the label alone, even with 100:1 and 20:1 ratios.

A ratio isn't a percentage. A percentage reports a measured marker in the finished extract. A ratio, as ODS describes it, compares the weight of dried plant that went in with the finished product that came out.

Read literally, 1 mg of the 100:1 longjack extract (Eurycoma longifolia root) traces back to about 100 mg of dried root, and 1 mg of the 20:1 polypody extract to about 20 mg of plant. Neither ratio says which compounds made it through. Our explainer on extract ratios and powders runs the same arithmetic on mushroom labels.

The rest of the panel is small too: every other row is 62.5 mg or less, from maca powder down to those two 1 mg extracts. We sell the formula exactly as our manufacturing partner specifies it (our quality page explains that setup), so we can't give you the reasoning behind each small row.

How should you take an icariin supplement, according to the label?

Take Betterly's Horny Goat Weed & Maca Capsules as the label says: 2 capsules once a day, and don't go over that dose.

Sixty capsules make 30 servings. The directions set no time or meal, so tie it to a habit you already have. The shell is gelatin, and the label lists the formula as gluten free and lactose free.

The tribulus capsules read differently: 3 capsules before bedtime, from a bottle of 90, in a vegetable capsule labeled vegan and gluten free. Each serving also carries 200 mg of magnesium (48% DV) and 30 mg of zinc (273% DV), so total those against any other magnesium or zinc you take. The ODS zinc fact sheet gives an adult upper limit of 40 mg a day from all sources, and its magnesium fact sheet gives 350 mg a day from supplements and medicines.

Pick one of our Epimedium formulas, not two. These two share Epimedium, longjack and saw palmetto rows, and with no icariin figure on the tribulus label, your combined icariin total couldn't be worked out. A third, our Tribulus & Ginseng Women's Libido Capsules, lists Epimedium inside a blend with no amount. Switching to another brand instead? Redo the division from that bottle's own serving size.

From our shop: Tribulus, Zinc & Magnesium Capsules — 750 mg of tribulus, 200 mg of magnesium (48% DV) and 30 mg of zinc (273% DV) per 3-capsule vegan serving, plus 50 mg of horny goat weed with no icariin figure, so choose it instead of, not alongside, the Horny Goat Weed & Maca Capsules.

When don't you need an icariin supplement?

You don't need a new icariin supplement, or a higher grade, just because a bigger percentage looks stronger.

A 60% or 98% figure measures concentration, and none of our sources ties a higher grade to anything beyond the number itself. We don't sell a purified icariin product anyway.

Nor do you need a fresh bottle to size up yours: if its panel prints extract weight and icariin, the division above answers the question. And pass on adding an Epimedium formula whose panel names no marker, since you'd have no way to count what it adds.

Our Targeted Support collection shows each Epimedium formula we carry with its full panel.

Who should check with a healthcare provider before taking icariin?

Talk to a healthcare provider before trying icariin if you take any medicine, are pregnant, nursing or under 18, have surgery booked, or manage a medical condition.

The bottles set the baseline. Our Horny Goat Weed & Maca caution sends anyone pregnant, nursing, under 18 or with a medical condition to a physician first. The tribulus label's warning goes further: no use at all if pregnant or lactating.

Two more flags come from the ingredients. PubChem lists "phytoestrogen," a plant compound with estrogen-like activity, among icariin's roles, so if you've been advised to avoid such compounds, mention icariin by name. Our Horny Goat Weed & Maca panel also carries 30 mg of L-phenylalanine per 2-capsule serving, which matters if your diet restricts that amino acid.

For medicines, hand a pharmacist the full panel. For surgery or dental work, put the product on the medication list your care team asks for.

FAQ: icariin

Is icariin the same as horny goat weed?

No, icariin isn't the same as horny goat weed. Icariin is one compound inside the plant. Horny goat weed is a nickname covering the whole Epimedium genus, which LiverTox says holds more than 200 identified constituents. A horny goat weed product may not state its icariin content, so check the panel for an icariin line under the extract.

Are icariin benefits proven?

No, icariin has no benefit proven in rigorous human trials in the federal sources we read. PubChem says icariin is only thought to be the main active ingredient of Herba Epimedii, and LiverTox lists it among flavonoids believed to be active in the plant. Neither wording is a finding in people. Our review of what horny goat weed research does and doesn't show walks through the human studies LiverTox summarizes.

What does "icariin 60" mean on a bottle?

In the listings we found, "icariin 60" refers to an Epimedium extract sold as 60% icariin. At that grade, every 100 mg of extract would hold 60 mg of icariin, and a 500 mg capsule would hold 300 mg. A product name isn't a measurement, though, so confirm the extract weight and icariin milligrams on the Supplement Facts panel.

Is pure icariin powder safer than an Epimedium extract?

No federal source we read shows that pure icariin powder is safer or riskier than an Epimedium extract. A 98% powder concentrates one compound, so each milligram carries far more icariin, and there's no federal upper limit to measure it against. Keep to the label's suggested use, and run it past a healthcare provider first if you're on any medication.

What is icariin found in?

Icariin is found in plants of the Epimedium genus. PubChem notes reports of it in species such as Epimedium brevicornu and Epimedium truncatum. Our capsules list Epimedium sagittatum, from the plant's leaves and stems. A different species on another label isn't a red flag: LiverTox's notes cite a review counting 52 species in the genus.

What time of day should you take icariin?

Our Horny Goat Weed & Maca label gives no time of day, only 2 capsules once a day, so any consistent time follows the directions. Our tribulus capsules differ: their label says 3 capsules before bedtime.

Sources

• Icariin (CID 5318997), PubChem (National Library of Medicine, National Institutes of Health)
• Horny Goat Weed, LiverTox (NCBI Bookshelf, National Institutes of Health)
• Botanical Dietary Supplements: Background Information for Consumers (NIH Office of Dietary Supplements)
• 21 CFR 101.36, Nutrition labeling of dietary supplements (Electronic Code of Federal Regulations)
• Zinc: Fact Sheet for Consumers (NIH Office of Dietary Supplements)
• Magnesium: Fact Sheet for Consumers (NIH Office of Dietary Supplements)

If this left you looking for somewhere to start, read horny goat weed extract with 100 mg of icariins — its amounts per serving are listed on the page. For the practical questions this raises, how dosing, sourcing and subscriptions work is answered in one place.