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What Is Horny Goat Weed?

The Herb That Is Often Called a "Natural Viagra"

Cathy Wong is a nutritionist and wellness expert. Her work is regularly featured in media such as First For Women, Woman's World, and Natural Health.

Meredith Bull, ND, is a licensed naturopathic doctor with a private practice in Los Angeles. She helped co-author the first integrative geriatrics textbook, "Integrative Geriatric Medicine."

Verywell / Anastasiia Tretiak

Horny goat weed is a plant used in traditional Chinese medicine. As its nickname, “natural Viagra,” implies, some people use horny goat weed to improve sexual function and arousal.

This article discusses the possible health benefits and side effects of taking horny goat weed. It also shares recommended doses and what to look for when buying this supplement.

Also Known As

  • Epimedium
  • Yin yan huo
  • Dâm dương hoắc

What Is Horny Goat Weed Used For?

The health and sexual benefit claims for horny goat weed go back thousands of years.

According to folklore, a Chinese goat herder noticed that his flock had heightened sexual activity after eating the plant. This led to the discovery of the plant's aphrodisiac (sexually stimulating) qualities. So, if you were wondering where this herbal remedy got its name, now you know.

Horny goat weed contains chemical compounds known as phytoestrogens , plant-based substances that have the same effects as the estrogen your body produces. This is why some people suggest that it can influence hormones and bone health.

Alternative medicine practitioners propose that horny goat weed is useful in complementary therapy to treat certain conditions.

Some claim that horny goat weed can improve circulation by thinning the blood. It has also been used to relieve symptoms of premenstrual syndrome (PMS), sharpen memory, and boost energy.

Few studies have looked at the benefits of horny goat weed. The main studies are in vitro (conducted in test tubes) or animal studies. Erectile dysfunction and bone disorders are the two most common conditions that have been studied.


Horny goat weed is sometimes used in alternative medicine. This herbal supplement may improve blood circulation and help treat bone diseases like osteoporosis and osteoarthritis.

Erectile Dysfunction

Quality research is lacking, but some evidence suggests horny goat weed can help males who have certain types of sexual dysfunction.

Horny goat weed contains a substance called icariin . Icariin can block a protein linked with erectile dysfunction called phosphodiesterase type 5 (PDE5).

PDE5 basically limits the increase in blood flow to the penis that is needed for an erection. Erectile dysfunction happens when there's not enough blood flowing to the penis.

Normally, the body curbs PDE5 levels. In people who have erectile dysfunction, PDE5 might not be controlled the way it should be.

Scientists found that icariin acts in the same way as Viagra ( sildenafil ) by blocking PDE5 activity. However, the action was weak, even in a test tube study. Compared to icariin, Viagra was 80 times more effective.

That’s not to say horny goat weed won't improve a man’s ability to have an erection. The supplement may increase blood flow enough to trigger an erection in people who have mild to moderate erectile dysfunction.

Bone and Joint Health

Phytoestrogens are plant-based estrogens found in horny goat weed and other plants. They can imitate the action of estrogen. Low estrogen levels after menopause can cause bone loss. Some alternative medicine practitioners suggest phytoestrogens can help treat this bone loss.

Scientists tested this theory in a 2007 study.

In the study, 85 late-postmenopausal women took either a placebo (sugar pill) or a phytoestrogen supplement extracted from horny goat weed. They all took 300 milligrams (mg) of calcium per day as well.

Two years later, horny goat weed extract appeared to help prevent bone loss. The phytoestrogen group had better bone turnover markers (the measure of how much new bone is being made to replace old bone tissue).

Horny goat weed wasn’t linked with any negative effects that women experience when taking estrogen, such as endometrial hyperplasia (irregular thickening of the uterine wall). In some cases, endometrial hyperplasia can lead to cancer of the uterus.

Additionally, a 2018 animal study looked at the effects of icariin, the substance extracted from horny goat weed. They found that icariin can help slow the breakdown of cartilage in the joints that causes osteoarthritis.

Cartilage is a tissue that helps cushion the joints and prevents bones from rubbing together. When there’s not enough cartilage to absorb shock, you may experience osteoarthritis symptoms like joint inflammation and stiffness.


Research found that the phytoestrogen in horny goat weed can help prevent bone loss in post-menopausal women. The women in the study also didn't experience any negative effects from the supplement.

Possible Side Effects

According to the National Institutes of Health (NIH), appropriate doses of horny goat weed are considered safe. High doses can be toxic to the kidneys and liver.

Talk to your healthcare provider before you use horny goat weed to treat any chronic condition. They can check to see if it would interact with any drugs you’re taking, such as blood thinners or blood pressure medications.

Certain people shouldn’t take horny goat weed:

  • Women who are pregnant or breastfeeding
  • People with bleeding disorders
  • Individuals with low blood pressure or irregular heartbeat
  • Women with hormone-sensitive conditions (endometriosis, uterine fibroids, and cancers of the breast, ovaries, or prostate)

Since horny goat weed can slow blood clotting, don’t use it before surgery.

Dosage and Preparation

You can find horny goat weed in many drug and health-food stores. It's available as a capsule, powder, tablet, or tea.

Some practitioners believe that an appropriate dose is 5 grams per day. However, more evidence is needed to recommend a specific dose.

Always check the label of any horny goat weed product you purchase. Similar varieties may have unwanted effects. Epimedium saggitatum and Epimedium grandiflorum are normally used in Chinese medicine.

What to Look For

Before taking this herbal supplement, talk to your healthcare provider. There are different variations of horny goat weed. Plus, not all of them are considered safe for all people. Your dosage and whether it's safe for you depends on several factors. These include your age, sex, and medical conditions.

If you do choose to take this supplement, the NIH recommends looking for a Supplement Facts label on the product you buy. This label contains important information, such as the amount of active ingredients per serving. It will also list other ingredients that may affect your health.

Look for a product that contains a seal of approval from a third-party organization that provides quality testing. These organizations include U.S. Pharmacopeia,, and NSF International.

A seal of approval from one of these organizations doesn't guarantee that the product is safe or effective. But it does assure you that it was properly made, contains the ingredients listed on the label, and doesn't have harmful levels of contaminants.


Horny goat weed is an herbal supplement that some people use to treat erectile dysfunction and stimulate sexual arousal. Some research suggests it has other positive effects, especially on bone health.

People who have certain conditions shouldn't take this supplement. Talk with your healthcare provider to determine if it's right for you.

Goat weed plant seeds

Photo 1. Mass of goatweed, Ageratum conyzoides.

Photo 2. Young group of goatweed plants, Ageratum conyzoides, with maturing flowers.

Photo 3. Seedlngs at flowering, goatweed plants, Ageratum conyzoides.

Photo 4. Goatweed, Ageratum conyzoides, with terminal and axillary flowers.

Goatweed; it is also known as billygoat weed (or billy goat weed, even billy-goat weed), tropic ageratum, blue flowered groundsel.

Ageratum conyzoides; previously, known by a large number of different names in the genera Ageratum, Cacalia and Eupatorium. It is also said to be Ageratum conyzoides subspecies conyzoides. It is a member of the Asteraceae.

A similar species, Ageratum houstonianum, is recorded in the Pacific islands (Fiji, French Polynesia, New Caledonia, Papua New Guinea).

Asia, Africa, North, South and Central America, the Caribbean, Oceania. It is recorded from Australia, American Samoa, Cook Islands, Federated States of Micronesia, Fiji, French Polynesia, Guam, Kiribati, Marshall Islands, Nauru, New Caledonia, Northern Mariana Islands, Palau, Papua New Guinea, Samoa, Tonga, Vanuatu, and Wallis & Futuna.

A native of tropical America, South and possibly Central America, and the Caribbean.

A major invasive weed in many regions of the word, capable of covering extensive areas (Photo 1). It occurs in natural habitats – grasslands, forests, wetlands, banks of water courses, coastal dunes – and also in disturbed habitats associated with human activities: crops (light and heavy soils), pastures, plantations, orchards, wastelands and roadsides.

Goat weed prefers moist, fertile soils; it is not suited to the dry less fertile soils of atolls.

Goatweed is an annual, erect, branching herb, 0.5-1 m high (Photo 2). Stems are soft becoming woody with age. Leaves, oval, but broader at the base, up to 7.5 cm long (Photo 3). Both young stems and leaves are covered with fine white hairs. When crushed the leaves have the smell of a male goat, hence the name. Plants have 4-18 flowerheads in a branched flat-topped cluster at the top of the stems or less commonly from branches off the main stem (Photos 4&5). Within each flowerhead, there are 30-50 white, light blue or violet flowers (Photos 6&7). The individual flowerheads are surrounded by two to three rows of leaf-like structures (Photo 5). The fruits are small, brown and one-seeded (Photo 8). The plants have shallow fibrous roots.

Another species Ageratum houstoniarum is similar (Photos 9&10): it has a larger number of flowers in each flower-head, 75-100, compared to 60-75 in Ageratum conyzoides, and the female parts of the flower, the style, are clearly seen above the green leaf-like structures surrounding the groups of flowers (Photo 11).

Spread occurs associated with the trade in ornamental plants, which subsequently escape from gardens. The weed is also spread as a contaminant of seed of other species, and also on people’s clothing as well as on machinery.

The impact from goatweed is both economic and environmental. It flowers year round, completes its life-cycle within 2 months, and produces large amounts of seed resulting in heavy infestations that lower crop yields, and are costly to control. Also, the growth of this weed over large areas (from coast to over 3000 masl) impacts biodiversity by preventing native species from establishing.

Goatweed is reported a problem in the following crops: maize (Ghana, Nigeria, the Philippines), peanut (Ghana, Indonesia, Sri Lanka), upland rice and chillies (Indonesia), cotton (Uganda), tea (Taiwan, India, Indonesia, Mauritius and Sri Lanka), cocoa (Brazil), potatoes (Colombia), oil palm (Nigeria), and over-grazed pastures (Australia, Hawaii, India). Yields are lower than expected, and labour costs for weed management are high.

It is poisonous to humans. Ingesting goat weed is said to cause liver lesions and tumours. There is a report of a mass poisoning in Ethiopia as a result of contamination of grain.

Goatweed hosts plant pathogens. For instance, it is a symptomless carrier of bacterial wilt (Ralstonia solanacearum), a host of the banana nematode (Radopholus similis), as well as the root knot nematatode (Meloidogyne javanica). There are reports as a host of virus diseases.

Probably, only eaten for medicinal purposes; the weed is used in many traditional medicines, covering a large number of common complaints. A wide range of chemical compounds including alkaloids, flavonoids, chromenes, benzofurans and terpenoids have been isolated from this species according to the IUCN. Insecticides and herbicides are included in the list of uses.

There is a high risk of goatweed becoming an invasive weed when grown outside its natural range. Once established, it is extremely difficult to control. Countries not yet infested should consider all likely pathways for entry, and apply quarantine measures accordingly. Special consideration should be given to the part played in the spread of this weed by the domestic and international trade in ornamental plants, as well as its use in traditional medicines. Seeds can be bought on the internet..

Ageratum conyzoides is on the Global Invasive Species Database (2020) of information about alien and invasive species that negatively impact biodiversity, managed by the Invasive Species Specialist Group of the IUCN Species Survival Commission.

Little known.

  • Physical & Mechanical
    • Hand weed (the weed is shallow rooted) where practical, before the plants have set seed. Follow-up as required.
    • Plough and disc the land, preferably before the plants have flowered and set seeds. Goatweed needs light to germinate, so burying the seeds should control its germination.
    • If practical, flood-fallow the land for a short period.
    • Treat vehicles and farm machinery. Wash down vehicles first before moving from areas where the weed occurs to those weed-free. Wash to remove soil and seed.
    • Ensure seeds are not carried on clothes between infested and ‘clean’ areas.

    In Australia: glyphosate (and Fiji); glufosinate-ammonium, are registered. In Fiji, 2,4-D.

    Note, EU approval to use glyphosate ends in December 2022; its use after that date is under discussion.

    When using a pesticide, always wear protective clothing and follow the instructions on the product label, such as dosage, timing of application, and pre-harvest interval.
    Recommendations will vary with the crop and system of cultivation. Expert advice on the most appropriate herbicides to use should always be sought from local agricultural authorities.

    Photo 5. Close-up flowerhead cluster, goatweed, Ageratum conyzoides. Note, each flowerhead surrounded by green, leaf-like structures.

    Photo 6. Close-up flowerhead, goatweed, Ageratum conyzoides.

    Photo 7. White flowers, goatweed, Ageratum conyzoides.

    Photo 8. Seeds, goatweed, Ageratum conyzoides.

    Photo 9. Blue billy goat weed, Ageratum houstonianum.

    Photo 10. Blue billy goat weed, Ageratum houstonianum.

    Photo 11. Comparison between flower-heads of Ageratum conyzoides (left) and Ageratum houstonianum (right).

    AUTHORS Grahame Jackson, Aradhana Deesh & Mani Mua
    Adapted from Billygoat weed (Ageratum conyzoides) (2018) Weeds of SE Qld and Northern NSW. Lucidcentral. (; and additional information from CABI (2019) Ageratum conyzoides (billy goat weed). Invasive Species Compendium. ( Photos 1,2,5&10,11 Sheldon Navie, Queensland, Australia. Photo 4 Minghong Photo of Ageratum conyzoides. Photos 8&9 Forest & Kim Starr. Starr Environmental,

    Produced with support from the Australian Centre for International Agricultural Research under project HORT/2016/185: Responding to emerging pest and disease threats to horticulture in the Pacific islands, implemented by the University of Queensland, in association with the Pacific Community and Koronivia Research Station, Ministry of Agriculture, Fiji.