Does horny goat weed increase testosterone levels in patients with low testosterone?

Horny Goat Weed and Testosterone: Evidence-Based Analysis

Horny goat weed (Epimedium species) does NOT increase testosterone levels in men with low testosterone, and there is no credible evidence supporting its use for this purpose. 1

What Horny Goat Weed Actually Does

The active compound in horny goat weed is icariin, which functions primarily as a phosphodiesterase type 5 (PDE5) inhibitor—similar to sildenafil (Viagra)—rather than as a testosterone booster 2. The mechanism is fundamentally different from testosterone replacement:

• Icariin may improve erectile function through PDE5 inhibition and potential neurotrophic effects on penile tissue, but this occurs independently of testosterone levels 2
• Animal studies show icariin increases neuronal nitric oxide synthase (nNOS) expression in penile tissue, which supports erectile function through improved blood flow, not hormonal changes 2
• No randomized controlled trials demonstrate testosterone elevation in humans taking horny goat weed 1

Evidence Quality Assessment

A systematic review of popular male testosterone supplements found that 68% of ingredients received C or D grades for contradicting, negative, or lacking evidence 1. Horny goat weed specifically:

• Was identified as one of the most common ingredients in over-the-counter testosterone supplements 1
• Has no published RCT evidence showing testosterone increases in humans 1
• Lacks any whole-product studies demonstrating efficacy for testosterone enhancement 1

Clinical Implications for Low Testosterone

If you have confirmed biochemical hypogonadism (morning total testosterone <300 ng/dL on two separate occasions with symptoms), the European Association of Urology strongly recommends against using supplements like horny goat weed and instead recommends evidence-based testosterone replacement therapy 3, 4.

For men with erectile dysfunction and low testosterone:

• The European Association of Urology recommends testosterone therapy as first-line treatment for hypogonadal patients with mild erectile dysfunction 3
• For more severe erectile dysfunction, combination therapy with PDE5 inhibitors (like sildenafil) and testosterone produces superior outcomes 3
• Horny goat weed's PDE5-inhibiting effects are vastly inferior to prescription medications and provide no testosterone benefit 1, 2

What Actually Increases Testosterone

Based on high-quality evidence, interventions that modestly improve testosterone in men with obesity-associated secondary hypogonadism include:

• Weight loss through low-calorie diets, which can reverse obesity-associated hypogonadism by improving testosterone levels 1-2 nmol/L 3
• Regular physical activity, with results correlating to exercise duration and weight loss 3
• Prescription testosterone replacement therapy remains the only treatment with substantial, clinically meaningful effects on testosterone levels 4

Supplements with Limited Evidence

A scoping review identified only a select few nutraceuticals with modest effects in well-controlled trials of men with low testosterone 5:

• Zinc (in deficiency states)
• Vitamin D (in hypovitaminosis D)
• Ashwagandha
• Mucuna

However, even these agents produce modest effects that do not directly translate into clinical benefits, and their use must be personalized by physicians 5.

Critical Caveat

The European Association of Urology explicitly recommends against testosterone therapy in eugonadal men (those with normal testosterone levels), even for weight loss, cardiometabolic improvement, cognition, vitality, or physical strength 3, 4. This same principle applies to supplements: if your testosterone is normal, neither prescription therapy nor supplements are appropriate.

Bottom Line Algorithm

1. If you have symptoms of low testosterone (diminished libido, erectile dysfunction): Get two morning testosterone measurements (8-10 AM) 4
2. If testosterone is confirmed low (<300 ng/dL): Pursue prescription testosterone replacement therapy, not supplements 3, 4
3. If you have erectile dysfunction with normal testosterone: Use PDE5 inhibitors (sildenafil, tadalafil), not horny goat weed 3
4. If you have obesity-associated low testosterone: Attempt weight loss and exercise first, then consider prescription therapy if unsuccessful 3
5. Never use horny goat weed expecting testosterone increases—the evidence simply does not exist 1