Horny Goat Weed and Icariin: What Human Studies Actually Tested
Written by the Horsewood Formula editorial desk
Last updated · Who reviewed this page · How we write and review
Human studies of horny goat weed are few, small and short, such as 63 men for two weeks on a multi-ingredient product. No clinical dose exists; products run 250 to 500 mg. Horsewood lists 8 mg of a 10:1 Epimedium sagittatum extract with no icariin percentage, and case reports of fast heart rhythm call for care.
What have human studies of horny goat weed actually tested?
Very little, and mostly in small groups. LiverTox says the claimed sexual benefits have not been proven in rigorous controlled trials (NIDDK LiverTox, 2022).
The human work it describes is small and short. One example enrolled 63 men for two weeks, and the product they took held several ingredients. A design like that cannot show what horny goat weed does on its own.
Drugs.com reaches the same view. It says controlled human trials are lacking (Drugs.com, 2026). So the herb has a long reputation and a short research record.
| Question | What the sources report |
|---|---|
| Large placebo-controlled trial of the herb alone? | None described in the sources used here |
| Example of a human trial | 63 men, 2 weeks, a multi-ingredient product |
| Proven sexual benefit? | Not proven in rigorous controlled trials |
| Clinical dose | No studies to base a dose on |
| Typical product size | 250 or 500 mg, usually once a day |
| Heart safety | Case reports of a fast heart rhythm |
What is Epimedium sagittatum, the species on the Horsewood label?
It is the plant the Horsewood label names for its horny goat weed. The common name covers several Epimedium species, so a label that prints the Latin name tells you more than one that does not.
The label line reads Epimedium sagittatum, 8 mg, from a 10:1 extract. It adds that this equals about 80 mg of dry horny goat weed powder.
What the label does not say
It gives no icariin percentage. It also does not say which part of the plant was extracted. Both gaps make the line hard to compare with other products.
What is icariin, and how much is in Horsewood?
Icariin is the compound horny goat weed products are usually standardized to. Drugs.com notes that commercial products are standardized to icariin (Drugs.com, 2026).
The Horsewood label does not state an icariin amount or percentage. That means the icariin in one serving is not published, and nobody outside the maker can work it out from the label.
Our Horsewood ingredients page lists each of the seven label lines with the amount printed for it.
What dose of horny goat weed do products and studies use?
No clinical dose exists. Drugs.com says there are no clinical studies to base one on, and that products on the market run 250 to 500 mg.
LiverTox describes the same sizes. Tablets and capsules are usually sold at 250 or 500 mg and taken once a day.
| Measure | Horsewood label | Common products |
|---|---|---|
| Extract per serving | 8 mg | 250-500 mg |
| Dry herb equivalent | About 80 mg (label) | Not stated in the sources used here |
| Icariin stated? | No | Usually standardized to icariin |
| Servings a day | 1 serving of 2 capsules | Usually 1 tablet or capsule |
| Studied as a single herb? | No study of the finished formula | Not in rigorous trials |
Compared extract to extract, 8 mg is roughly one thirtieth to one sixtieth of a typical product. Even the 80 mg dry-herb figure is well under the low end of that range. No study shows what 8 mg does, high or low.
How should you read a 10:1 extract line like the one on Horsewood?
Read it as a recipe, not a dose. The ratio says how much raw herb was used to make the extract, and the capsule holds only the extract.
The steps below walk through the horny goat weed line one piece at a time.
- 1
Start with the dry herb
About 80 mg of dried horny goat weed goes into the process for each serving.
- 2
Concentrate it ten times
Extraction removes most of the plant mass. Ten parts of herb become one part of extract.
- 3
Look at what is in the capsule
The serving holds 8 mg of extract. That is the amount you swallow.
- 4
Check for a marker compound
A strength claim needs an icariin percentage. This label does not give one.
- 5
Compare with like for like
Set 8 mg of extract against 250-500 mg products, not against the 80 mg figure.
Why do rat and lab studies not settle the question?
Because people are not rats, and a lab dish is not a body. Animal results can point to something worth testing, but they cannot prove a human effect or a safe human dose.
The FTC holds health claims to the same standard. Its guidance says claims need good human trials, and the product's dose and formula should match what was studied (FTC, 2022).
- Animal doses rarely match what a person takes
- Lab tests on a single compound skip how the body absorbs it
- Short trials in a few people can miss side effects
- A blend of herbs hides which one did the work
No study of the finished Horsewood formula has been published. So any claim about the blend rests on research about single ingredients at other doses.
Is horny goat weed safe for the heart and blood pressure?
It has not been shown to be safe for people with heart disease. Drugs.com reports case reports of a fast heart rhythm and rash, especially in older people with heart disease (Drugs.com, 2026).
Reports of heart rhythm and blood pressure effects are the reason this herb deserves care. It is not a treatment for high or low blood pressure.
Erection problems also deserve a doctor's visit on their own. In a large study, men who developed ED had about a 25% higher risk of later heart and blood vessel events (Thompson et al., 2005). The Horsewood side effects page covers the other label ingredients.
Does horny goat weed raise testosterone?
The sources reviewed for this site do not report a human trial that shows it. Claims about testosterone usually come from ads, not from controlled studies in men.
Horsewood is not a treatment for low testosterone. If you have low energy or low desire, a blood test gives a real answer. Our post on boron and testosterone looks at another label ingredient often tied to testosterone, and the small study behind that idea.
Where does horny goat weed fit in Horsewood?
It is one small line among seven. The Horsewood serving lists 118 mg of label ingredients in total, and horny goat weed is the smallest amount at 8 mg.
That honesty about amounts is useful, because you can compare each line with the research yourself. The research simply does not give horny goat weed a proven dose to compare against.
What the horny goat weed line tells you: 0 of 5 checked
If you still want to try Horsewood as a daily routine, the pricing page lists the 2-, 3- and 6-bottle packs. The checkout shows the final total before you pay.
Horny goat weed and icariin: common questions
Common search questions, answered from the label and the sources cited on this page.
Has horny goat weed been tested in humans?
Only a little. LiverTox describes small human trials, such as one in 63 men that lasted two weeks and used a product with several ingredients. No rigorous controlled trial has proven a sexual benefit.
How much icariin is in horny goat weed?
It varies from product to product, which is why many brands state an icariin percentage. The Horsewood label does not print one, so its icariin content is not published.
What dose of horny goat weed is used?
No clinical study sets a dose. Products on the market are usually sold as 250 or 500 mg tablets or capsules, often taken once a day.
Is horny goat weed safe for the heart?
Not proven safe for people with heart disease. Case reports describe a fast heart rhythm, mostly in older adults with heart problems, so ask your doctor first if you have a heart condition or take heart medicine.
Does horny goat weed raise testosterone?
The sources used on this site do not report a human trial showing that. Horsewood is not a testosterone treatment, and low testosterone needs a blood test and a doctor.
What is Epimedium sagittatum?
It is the species of horny goat weed named on the Horsewood label. Several Epimedium plants are sold under the same common name, so naming the species is a useful detail.
Can horny goat weed lower blood pressure?
It is not a blood pressure treatment. Case reports link it to heart rhythm and blood pressure effects, so anyone on blood pressure medicine should check with a doctor or pharmacist first.
Are rat studies on horny goat weed meaningful for people?
They can suggest what to test, but they cannot prove a human effect or a human dose. The FTC expects health claims to rest on good human trials that match the product's dose and formula.
