Horny goat weed (Epimedium) is a traditional Chinese herbal remedy widely marketed for erectile dysfunction, but does goat weed help with erectile dysfunction in practice? Whilst laboratory studies suggest its active compound, icariin, may inhibit the same enzymes targeted by prescription medicines like sildenafil, the clinical evidence in men remains limited and of low quality. Most horny goat weed products in the UK are unregulated food supplements, not licensed medicines, meaning their potency, purity, and safety are not guaranteed. This article examines the evidence, safety concerns, and NHS-recommended alternatives for managing erectile dysfunction.
Summary: Horny goat weed has not been proven to effectively treat erectile dysfunction in high-quality human trials, and it is not recommended by NICE or licensed by the MHRA for this use.
- Horny goat weed contains icariin, which may inhibit PDE5 enzymes in laboratory studies, but is far less potent than licensed medicines like sildenafil.
- Clinical evidence in men is insufficient, with no robust randomised controlled trials demonstrating meaningful benefit for erectile dysfunction.
- Most UK products are unregulated food supplements with variable icariin content, and some may contain undeclared pharmaceutical ingredients.
- Potential side effects include dizziness, nausea, and interactions with nitrates, PDE5 inhibitors, and anticoagulants, which can cause serious complications.
- NHS-recommended first-line treatments are lifestyle changes and PDE5 inhibitors (sildenafil, tadalafil, vardenafil, avanafil), which have proven efficacy and safety.
- Men with persistent erectile dysfunction should consult their GP for assessment, as it may signal underlying cardiovascular disease or diabetes.
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What Is Horny Goat Weed and How Does It Work?
Horny goat weed (Epimedium) is a traditional Chinese herbal remedy that has been used for centuries to address sexual dysfunction and low libido. The plant contains several bioactive compounds, the most studied being icariin, which is thought to be responsible for its purported effects on erectile function.
In laboratory and animal studies, icariin has been shown to inhibit phosphodiesterase type 5 (PDE5) enzymes—the same target as prescription medicines such as sildenafil (Viagra). In principle, PDE5 inhibition may increase blood flow to the penis by promoting the relaxation of smooth muscle tissue and dilation of blood vessels. However, it is important to note that icariin is far less potent than licensed PDE5 inhibitors in these preclinical models, and there is no established, standardised therapeutic dose of icariin for erectile dysfunction in humans.
The concentration of icariin varies significantly between different preparations and species of Epimedium. Most horny goat weed products sold in the UK are classified as food supplements, not licensed medicines, and are not subject to the same regulatory standards as medicines approved by the MHRA. This means the actual dose of active ingredient can be unpredictable, and the bioavailability of icariin—how much is actually absorbed and utilised by the body—remains poorly understood.
A small number of herbal products containing Epimedium may carry a Traditional Herbal Registration (THR) logo, indicating they meet certain quality and safety standards, but this does not confirm efficacy for erectile dysfunction. Whilst the theoretical mechanism is plausible based on laboratory data, the evidence supporting horny goat weed as an effective treatment for erectile dysfunction in humans is limited. Most research has been conducted in animal models or laboratory settings, and there is a lack of robust clinical trials in men with erectile dysfunction. As such, whilst horny goat weed is widely marketed as a natural remedy, its efficacy and safety profile have not been established to the standards required by the MHRA or EMA.
Evidence for Goat Weed in Treating Erectile Dysfunction
The clinical evidence supporting the use of horny goat weed for erectile dysfunction is currently insufficient and of low quality. Whilst laboratory and animal studies suggest that icariin may have PDE5-inhibiting properties, there is a significant gap in high-quality human trials that demonstrate meaningful clinical benefit.
A small number of studies have explored the effects of Epimedium extracts in men, but these are often limited by small sample sizes, lack of placebo controls, and inconsistent dosing regimens. Some preliminary research has suggested modest improvements in erectile function scores, but these findings have not been replicated in larger, well-designed randomised controlled trials. Consequently, there is no official link established between horny goat weed supplementation and clinically significant improvement in erectile dysfunction.
Furthermore, the lack of standardisation in herbal supplements means that study results may not be generalisable. Different products contain varying amounts of icariin and other compounds, making it difficult to compare outcomes or recommend specific formulations. The absence of regulatory oversight also raises concerns about product quality, purity, and the potential presence of undeclared ingredients. The MHRA has issued warnings about erectile dysfunction supplements purchased online that have been found to contain undeclared pharmaceutical agents, including analogues of sildenafil and tadalafil, which can pose serious health risks.
There are no MHRA-licensed Epimedium products for erectile dysfunction in the UK. NICE guidance on the management of erectile dysfunction (NICE CKS: Erectile dysfunction) does not currently recommend herbal supplements such as horny goat weed. Instead, evidence-based treatments with proven efficacy and safety profiles—such as PDE5 inhibitors—are advised as first-line pharmacological options. Patients considering herbal remedies should be aware that these products are not subject to the same rigorous testing and approval processes as licensed medicines, and their use should be discussed with a healthcare professional to ensure informed decision-making and avoid potential interactions with other treatments.
Safety, Side Effects and Drug Interactions
Whilst horny goat weed is often marketed as a natural and safe alternative to prescription medications, it is not without potential risks. Human safety data are limited, but reported side effects in the literature and case reports include dizziness, dry mouth, nosebleeds, nausea, and vomiting. Some users have also experienced increased heart rate and mood changes, although these effects are not well characterised in clinical studies.
Of particular concern is the potential for drug interactions. Because icariin may act similarly to PDE5 inhibitors, combining horny goat weed with prescription erectile dysfunction medications such as sildenafil, tadalafil, vardenafil, or avanafil could theoretically lead to additive effects, increasing the risk of hypotension (dangerously low blood pressure), dizziness, and cardiovascular complications. Men taking nitrates for angina or riociguat for pulmonary hypertension should avoid horny goat weed, as the combination could result in severe drops in blood pressure. Caution is also advised in men taking alpha-blockers or other antihypertensive medicines.
Additionally, horny goat weed may interact with anticoagulant or antiplatelet medications (such as warfarin or aspirin), potentially increasing bleeding risk. There is limited information on its effects in individuals with liver or kidney impairment, or on interactions with medicines metabolised by cytochrome P450 enzymes. If you take any regular medicines, it is important to check with your GP or pharmacist before using horny goat weed.
Quality and contamination are further safety concerns. Herbal supplements are not subject to the same regulatory standards as licensed medicines in the UK. The MHRA has found that some erectile dysfunction supplements purchased online contain undeclared pharmaceutical ingredients, heavy metals, or other contaminants. Patients should be cautious about purchasing supplements from unverified sources. If you choose to use a herbal product, look for the Traditional Herbal Registration (THR) logo and buy from reputable UK sources.
If you experience any suspected side effects from horny goat weed or any other supplement, you can report them via the MHRA Yellow Card scheme at yellowcard.mhra.gov.uk or through the Yellow Card app.
Anyone considering horny goat weed should discuss it with their GP or pharmacist, particularly if they have underlying health conditions, take regular medications, or are already using treatments for erectile dysfunction. Self-medicating with unregulated supplements can delay appropriate diagnosis and treatment of underlying causes of erectile dysfunction, such as cardiovascular disease or diabetes.
NHS-Recommended Treatments for Erectile Dysfunction
The NHS and NICE recommend a structured, evidence-based approach to managing erectile dysfunction, beginning with lifestyle modifications and progressing to pharmacological treatments when appropriate. First-line management includes addressing modifiable risk factors such as smoking, excessive alcohol consumption, obesity, and physical inactivity. Regular exercise, a balanced diet, and weight loss (if overweight) can significantly improve erectile function and overall cardiovascular health.
When lifestyle changes alone are insufficient, PDE5 inhibitors are the recommended first-line pharmacological treatment. These include:
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Sildenafil (Viagra)
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Tadalafil (Cialis)
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Vardenafil (Levitra)
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Avanafil (Spedra)
These medications work by enhancing the natural erectile response to sexual stimulation, and they have been extensively studied in clinical trials with proven efficacy and safety. Sildenafil 50 mg is available without prescription from pharmacies as Viagra Connect, following an assessment by a pharmacist to ensure it is safe and appropriate for you.
PDE5 inhibitors may be available on NHS prescription for men with erectile dysfunction, particularly when there is an underlying medical cause such as diabetes, cardiovascular disease, prostate surgery, or certain other conditions. NHS prescribing is subject to specific criteria, and in some cases treatment may be available if erectile dysfunction is causing severe distress. Your GP can advise on NHS eligibility and prescribing arrangements in your area.
For men who do not respond to or cannot tolerate PDE5 inhibitors, second-line treatments may include:
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Vacuum erection devices (mechanical pumps that draw blood into the penis)
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Intracavernosal injections (medications injected directly into the penis)
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Intraurethral therapy (medicated pellets inserted into the urethra)
In men with confirmed hypogonadism (low testosterone), testosterone replacement therapy may be appropriate and should be discussed with your GP or an endocrinologist.
In some cases, psychological or relationship counselling may be beneficial, particularly when erectile dysfunction has a significant psychogenic component or is affecting intimate relationships. The NHS may offer referral to psychosexual therapy services.
Surgical options, such as penile implants, are generally reserved for men with severe erectile dysfunction who have not responded to other treatments. NICE emphasises the importance of a holistic assessment, including screening for underlying conditions such as hypertension, diabetes, and depression, all of which can contribute to erectile dysfunction. Your GP may refer you to specialist services such as urology (for treatment failures or structural concerns), endocrinology (for suspected hormonal issues), or cardiology (if cardiovascular risk is high).
When to See Your GP About Erection Problems
Erectile dysfunction is very common, particularly in men over 40. Whilst occasional difficulty achieving or maintaining an erection is normal, persistent problems warrant medical evaluation. Men should consider seeing their GP if erectile difficulties occur regularly, cause distress, or affect their quality of life and relationships.
Key reasons to seek medical advice include:
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Erectile dysfunction persisting for more than a few weeks
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Sudden onset of erection problems, particularly in younger men
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Associated symptoms such as reduced libido, fatigue, or mood changes
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Concerns about underlying health conditions
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Relationship difficulties related to sexual function
Erectile dysfunction can be an early warning sign of cardiovascular disease, as the blood vessels supplying the penis are smaller than coronary arteries and may show signs of atherosclerosis earlier. A GP assessment will typically include a medical history, physical examination, and blood tests to check for conditions such as diabetes, high cholesterol, and thyroid disorders. If you have symptoms such as low libido or fatigue, your GP may arrange a morning total testosterone test to check for hypogonadism. In younger men with persistent erectile dysfunction, cardiovascular risk assessment (including blood pressure, lipids, and HbA1c) is particularly important.
You should also see your GP if you notice:
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New penile curvature, deformity, or pain (which may suggest Peyronie's disease)
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A palpable lump or mass in the testicles
Men should seek urgent medical attention if they experience:
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Chest pain or breathlessness during sexual activity
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Prolonged, painful erections lasting more than four hours (priapism)
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Sudden loss of vision or hearing after taking erectile dysfunction treatments
It is important to be open and honest with your GP about erectile difficulties, any supplements or medications you are taking (including herbal remedies), and lifestyle factors. Erectile dysfunction is a medical condition, not a reflection of masculinity, and effective, evidence-based treatments are available. Early consultation can help identify and manage underlying health issues, improve sexual function, and enhance overall wellbeing. Your GP can provide tailored advice, prescribe appropriate treatments, and refer you to specialist services if needed.
Frequently Asked Questions
Can I take horny goat weed with Viagra or other erectile dysfunction tablets?
No, you should not combine horny goat weed with prescription PDE5 inhibitors such as sildenafil (Viagra), tadalafil, vardenafil, or avanafil. Both may lower blood pressure, and taking them together could lead to dangerously low blood pressure, dizziness, and cardiovascular complications.
Is horny goat weed safe if I'm taking medication for high blood pressure or heart problems?
Horny goat weed may interact with antihypertensive medicines, nitrates, and alpha-blockers, potentially causing severe drops in blood pressure. Men taking nitrates for angina or riociguat for pulmonary hypertension should avoid it entirely, and anyone on cardiovascular medication should consult their GP or pharmacist before use.
What's the difference between horny goat weed and prescription erectile dysfunction treatments?
Prescription PDE5 inhibitors like sildenafil are licensed medicines with proven efficacy, standardised doses, and rigorous safety testing by the MHRA. Horny goat weed is an unregulated food supplement with variable icariin content, no established therapeutic dose, and insufficient clinical evidence in men with erectile dysfunction.
How do I know if a horny goat weed supplement is safe to use?
Look for the Traditional Herbal Registration (THR) logo and purchase only from reputable UK sources. The MHRA has found that some erectile dysfunction supplements sold online contain undeclared pharmaceutical ingredients, heavy metals, or contaminants, which can pose serious health risks.
Will my GP prescribe horny goat weed for erectile dysfunction on the NHS?
No, horny goat weed is not an MHRA-licensed medicine and is not recommended by NICE for erectile dysfunction. Your GP can prescribe evidence-based treatments such as PDE5 inhibitors (sildenafil, tadalafil, vardenafil, avanafil), which are available on the NHS for eligible patients with underlying medical causes or severe distress.
When should I see my GP instead of trying herbal remedies for erection problems?
You should see your GP if erectile difficulties persist for more than a few weeks, cause distress, or are accompanied by symptoms like reduced libido, fatigue, or mood changes. Erectile dysfunction can be an early warning sign of cardiovascular disease or diabetes, and your GP can arrange appropriate tests, identify underlying causes, and recommend safe, effective treatments.
The health-related content published on this site is based on credible scientific sources and is periodically reviewed to ensure accuracy and relevance. Although we aim to reflect the most current medical knowledge, the material is meant for general education and awareness only.
The information on this site is not a substitute for professional medical advice. For any health concerns, please speak with a qualified medical professional. By using this information, you acknowledge responsibility for any decisions made and understand we are not liable for any consequences that may result.
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