horny goat weed

Medically Reviewed on 3/16/2022

Generic Name: horny goat weed

Brand and Other Names: epimedium spp, herba epimedii, icariin, inyokaku, yin yang huo

Drug Class: Herbals

What is horny goat weed, and what is it used for?

Horny goat weed is an herbal supplement made from species of Epimedium genus of flowering plants. Horny goat weed has been used in Traditional Chinese Medicine for centuries. People take horny goat weed for erectile dysfunction, sexual problems, weak and brittle bones, high blood pressure and health problems with menopause, however, there is insufficient scientific evidence for its benefits.

An animal study found that icariin, the active compound in horny goat weed, may work like sildenafil (Viagra), a medication used to treat erectile dysfunction. Sildenafil helps maintain an erection by improving blood flow to the penis. Sildenafil works by blocking an enzyme known as phosphodiesterase 5 (PDE5) that limits blood flow. Icariin is also found to have PDE5 blocking properties but far weaker than sildenafil.

Horny goat weed may also have phytoestrogens, which are plant-based estrogens that may act like estrogen and reduce bone loss in postmenopausal women. Icariin is also believed to slow down the wearing out of cartilage in joints. Horny goat weed may have antioxidant properties.

Horny goat weed is usually available in drug and health food stores in the form of tablets, capsules, powders or tea. Suggested uses of horny goat weed include the following:


  • Do not take if you are hypersensitive to horny goat weed or any of its ingredients
  • Short-term use is possibly safe; however, long-term or high doses may cause serious side effects including severe breathing problems
  • Horny goat weed use in pregnancy and breastfeeding is possibly unsafe; avoid use
  • Do not take if you have any bleeding disorders; horny goat weed slows down clotting and may increase bleeding risk
  • Stop taking horny goat weed at least two weeks before any surgery; it may increase bleeding risk
  • Horny goat weed has estrogen-like properties and may increase estrogen level; do not take if you have estrogen-sensitive conditions such as breast or uterine cancer

What are the side effects of horny goat weed?

Side effects of horny goat weed may include:

This is not a complete list of all side effects or adverse reactions that may occur from the use of this drug.

Call your doctor for medical advice about serious side effects or adverse reactions. You may also report side effects or health problems to the FDA at 1-800-FDA-1088.


What are the dosages of horny goat weed?

There isn't enough reliable information to know what might be an appropriate dose of horny goat weed. Natural products are not always necessarily safe and dosages can be important. Follow directions on product labels and consult a healthcare professional before using.

Suggested dosage:

  • 2 capsules (1000 mg, may vary with manufacturer) orally per day
  • 3-4 capsules orally 90 minutes before sexual activity
  • May also be taken as a tea
  • Preventing osteoporosis: a specific phytoestrogen extract of Epimedium containing 60 mg icariin, 15 mg daidzein, and 3 mg genistein, along with 300 mg of elemental calcium orally every day


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What drugs interact with horny goat weed?

Inform your doctor of all medications you are currently taking, who can advise you on any possible drug interactions. Never begin taking, suddenly discontinue, or change the dosage of any medication without your doctor’s recommendation.

  • Horny goat weed has no known severe interactions with other drugs.
  • Horny goat weed has no known serious interactions with other drugs.
    • Horny goat weed may have moderate interactions with the following drugs:
      • Estrogens
      • Antihypertensive drugs
      • Anticoagulant/antiplatelet drugs
      • Medications changed and broken down by the liver:
        • Cytochrome P450 1A2 (CYP1A2) substrates
        • Cytochrome P450 2B6 (CYP2B6) substrates
  • Horny goat weed may have interactions with the following herbs and supplements:
  • Horny goat weed has no known mild interactions with other drugs.
  • Horny goat weed has no known interactions with foods.

The drug interactions listed above are not all of the possible interactions or adverse effects. For more information on drug interactions, visit the RxList Drug Interaction Checker.

It is important to always tell your doctor, pharmacist, or health care provider of all prescription and over-the-counter medications you use, as well as the dosage for each, and keep a list of the information. Check with your doctor or health care provider if you have any questions about the medication.

Pregnancy and breastfeeding

  • Avoid using horny goat weed in pregnancy. It might cause fetal harm.
  • Avoid use while breastfeeding. There isn’t enough information to know if horny goat weed use is safe in nursing mothers.

What else should I know about horny goat weed?

  • Natural products are not always necessarily safe; exercise caution.
  • Studies on horny goat weed have mainly been done in labs or on animals. There is insufficient scientific information on its safety and efficacy in humans.
  • Always check labels for ingredients; horny goat weed formulations may often contain multiple ingredients.
  • Horny goat weed is marketed as a dietary supplement and does not require extensive pre-marketing approval from the FDA. There may sometimes be discrepancy between the labeling and the actual ingredients and their amounts.
  • The FDA has warned against the use of unregistered supplements including horny goat weed because they haven’t been evaluated by the FDA for safety. Make sure you use supplements registered with the FDA.
  • The FDA has issued warnings against some horny goat weed formulations containing chemical compounds structurally similar to sildenafil, the prescription drug used to treat erectile dysfunction, which they claim to replace with the natural product.


Horny goat weed is an herbal supplement that is used for erectile dysfunction, ejaculation problems, low sexual drive, joint pain, osteoporosis, postmenopausal health problems, fatigue, heart disease, and bronchitis. Side effects of horny goat weed may include vomiting, dry mouth, thirst, nosebleed, dizziness, fainting, low blood pressure (hypotension), irregular heart rhythms (arrhythmia), severe breathing problems, muscle spasms, increased risk of bleeding, and increase in blood clotting time. Do not take horny goat weed if pregnant or breastfeeding.

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Medically Reviewed on 3/16/2022