Background

Horny goat weed refers to various herb species of the Epimedium genus, and may be known as "yin yang huo." It has limited evidence of health benefits.

Horny goat weed contains chemicals that might help increase blood flow and improve sexual function. It also contains phytoestrogens, chemicals that act somewhat like the hormone estrogen.

People use horny goat weed for erectile dysfunction (ED), sexual problems, weak and brittle bones, health problems after menopause, and other conditions, but there is no good scientific evidence to support any of these uses.

Safety Safety definitions

When taken by mouth: Horny goat weed extract is possibly safe when used short-term. A specific extract of horny goat weed containing phytoestrogens has been taken by mouth safely for up to 2 years. Another extract containing a chemical called icariin has been taken safely for up to 6 months.

But some types of horny goat weed are possibly unsafe when used for a long period of time or in high doses. Serious side effects including severe breathing problems have been reported.

Special Precautions & Warnings:

Pregnancy: Horny goat weed is possibly unsafe when taken by mouth during pregnancy. It might harm the developing fetus. Avoid using it.

Breast-feeding: There isn't enough reliable information to know if horny goat weed is safe to use when breast-feeding. Stay on the safe side and avoid use.

Bleeding disorders: Horny goat weed might slow blood clotting. This might increase the risk of bleeding. Taking horny goat weed might make bleeding disorders worse.

Hormone sensitive cancers and conditions: Horny goat weed acts like estrogen and can increase estrogen levels in some people. Horny goat weed might worsen some estrogen-sensitive conditions, such as breast and uterine cancer.

Surgery: Horny goat weed might slow blood clotting. This might increase the risk of bleeding during surgery. Stop taking horny goat weed at least 2 weeks before surgery.

Effectiveness

Dosing & administration

There isn't enough reliable information to know what an appropriate dose of horny goat weed might be. Keep in mind that natural products are not always necessarily safe and dosages can be important. Be sure to follow relevant directions on product labels and consult a healthcare professional before using.

Interactions with pharmaceuticals

Estrogens

Interaction Rating=Moderate Be cautious with this combination.

Horny goat weed might have some of the same effects as estrogen and might increase blood levels of estrogen in some people. Taking horny goat weed with estrogen might increase the effects and side effects of estrogen.

Medications changed by the liver (Cytochrome P450 1A2 (CYP1A2) substrates)

Interaction Rating=Moderate Be cautious with this combination.

Some medications are changed and broken down by the liver. Horny goat weed might change how quickly the liver breaks down these medications. This could change the effects and side effects of these medications.

Medications changed by the liver (Cytochrome P450 2B6 (CYP2B6) substrates)

Interaction Rating=Moderate Be cautious with this combination.

Some medications are changed and broken down by the liver. Horny goat weed might change how quickly the liver breaks down these medications. This could change the effects and side effects of these medications.

Medications changed by the liver (Cytochrome P450 3A4 (CYP3A4) substrates)

Interaction Rating=Moderate Be cautious with this combination.

Some medications are changed and broken down by the liver. Horny goat weed might change how quickly the liver breaks down these medications. This could change the effects and side effects of these medications.

Medications for high blood pressure (Antihypertensive drugs)

Interaction Rating=Moderate Be cautious with this combination.

Horny goat weed might lower blood pressure. Taking horny goat weed along with medications that lower blood pressure might cause blood pressure to go too low. Monitor your blood pressure closely.

Medications that slow blood clotting (Anticoagulant / Antiplatelet drugs)

Interaction Rating=Moderate Be cautious with this combination.

Horny goat weed might slow blood clotting. Taking horny goat weed along with medications that also slow blood clotting might increase the risk of bruising and bleeding.

Interactions with herbs & supplements

Caffeine-containing herbs and supplements: Horny goat weed contains an ingredient that might slow down how quickly the body processes caffeine. Taking it with caffeine-containing herbs and supplements might increase the effects and side effects of caffeine. Examples of supplements that contain caffeine include black tea, coffee, green tea, guarana, and yerba mate.
Herbs and supplements that might lower blood pressure: Horny goat weed might lower blood pressure. Taking it with other supplements that have the same effect might cause blood pressure to drop too much. Examples of supplements with this effect include andrographis, casein peptides, L-arginine, niacin, and stinging nettle.
Herbs and supplements that might slow blood clotting: Horny goat weed might slow blood clotting and increase the risk of bleeding. Taking it with other supplements with similar effects might increase the risk of bleeding in some people. Examples of supplements with this effect include garlic, ginger, ginkgo, nattokinase, and Panax ginseng.

Interactions with foods

There are no known interactions with foods.