Tribulus Terrestris: Zero Evidence for Testosterone
Tribulus terrestris is sold across gym retail as a “natural testosterone booster,” but in healthy men with a placebo control it does not raise testosterone. A 2025 systematic review in Nutrients pooling 10 trials in 483 men found no robust androgen effect — the only small bumps (a clinically minor 60–70 ng/dL) came from men who were hypogonadal at baseline, not those with normal levels — and cleaner trials in young men and elite rugby players likewise showed no change in testosterone, strength, or body composition. The one nuance is that a few small, low-certainty trials suggest tribulus might modestly help erectile function, but that signal is independent of testosterone and most plausibly comes from nitric-oxide effects, not the hormonal axis. The original claim traces to a rodent-to-human translation failure, and because herbal “test booster” blends are a recurring source of contamination with undeclared anabolic agents, tested athletes should be especially wary of the category.
The Origins of the Claim
The testosterone story traces back to Eastern European athlete anecdotes from the 1970s and 1980s, plus animal studies suggesting that the steroidal saponins in the plant (chiefly protodioscin) might stimulate luteinizing hormone (LH) production and, indirectly, testosterone. Some rodent studies did report changes in sexual behavior and hormone markers. The mistake was assuming the same mechanism would carry over to healthy human men. Rats and humans regulate the hypothalamic-pituitary-gonadal axis differently, and compounds that move LH in rodents often do nothing to it in humans. This rodent-to-human translation failure is one of the most common sources of inflated supplement claims, and tribulus is a textbook example. A 2014 systematic review covering both human and animal data concluded that the human evidence does not support a testosterone-raising effect and that marketing claims are unsubstantiated; the authors proposed that any physiological response is more plausibly explained by nitric-oxide-mediated effects than by a change in androgen levels [5].
Results across human placebo-controlled trials
What the Clinical Trials Show
When tribulus is tested in healthy men with a placebo group, the testosterone signal disappears. In one of the cleaner trials, Neychev and Mitev gave young men (aged 20–36) 10 or 20 mg/kg of body weight per day of a standardized tribulus extract for four weeks and measured testosterone, androstenedione, and LH at six time points. There was no significant difference from placebo on any of the three hormones; all values stayed within the normal range [2]. In athletic populations the result is the same for performance: a five-week, double-blind, placebo-controlled trial in elite rugby players (450 mg/day) found no extra gain in strength or lean mass beyond training alone, and no change in the urinary testosterone-to-epitestosterone ratio [3]. An eight-week trial in resistance-trained men (about 3.2 mg/kg/day) likewise found no improvement in body composition or performance over placebo [4].
The largest synthesis to date is a 2025 systematic review in Nutrients that pooled 10 studies covering 483 men aged 16 to 70 across a range of health conditions [1]. Doses ran from 400 to 750 mg/day for one to three months. Eight of the ten studies reported no significant change in the androgen profile; the only two that showed a small intra-group rise in total testosterone (a clinically minor 60–70 ng/dL) involved men who were hypogonadal at baseline, not healthy men with normal levels. The reviewers rated methodological quality as low in half the studies (Jadad score) and concluded there is no robust evidence that tribulus raises testosterone.
The Libido and Erectile-Function Question
The more nuanced finding is that tribulus may do something for sexual function that is unrelated to testosterone. In the same 2025 review, three of five trials that assessed erectile dysfunction reported improvement on tribulus — but the certainty is low, the trials were small and short, and the benefit appeared even though testosterone did not move [1]. The leading mechanistic explanation is that tribulus saponins increase nitric oxide release, which would improve erectile response without touching the hormonal axis [5]. That is a meaningfully different claim from "natural testosterone booster," and the evidence is still too thin and too low-quality to support a clinical recommendation. If erectile dysfunction is the actual concern, it warrants medical evaluation rather than a gym-shelf saponin extract.
Why It Remains on Shelves
Under the U.S. Dietary Supplement Health and Education Act, products do not have to prove efficacy before sale; the burden falls on regulators to prove harm afterward. Manufacturers therefore lean on rodent studies, centuries of traditional use, and mechanistic hypotheses — none of which substitute for placebo-controlled human trials. Consumers reasonably but mistakenly assume that nationwide retail availability implies proof of effect. There is also an anti-doping wrinkle: although one trial found tribulus did not push the urinary T:E ratio past the World Anti-Doping Agency threshold [3], herbal "test booster" blends are a recurring source of contamination with undeclared anabolic agents, so tested athletes should be cautious about products in this category regardless of the headline ingredient.
Sources
- Vilar Neto JO, de Moraes WMAM, Pinto DV, et al. "Effects of Tribulus (Tribulus terrestris L.) Supplementation on Erectile Dysfunction and Testosterone Levels in Men—A Systematic Review of Clinical Trials." Nutrients, 2025;17(7):1275. PMID 40219032.
- Neychev VK, Mitev VI. "The aphrodisiac herb Tribulus terrestris does not influence the androgen production in young men." Journal of Ethnopharmacology, 2005;101(1-3):319-23. PMID 15994038.
- Rogerson S, Riches CJ, Jennings C, et al. "The effect of five weeks of Tribulus terrestris supplementation on muscle strength and body composition during preseason training in elite rugby league players." Journal of Strength and Conditioning Research, 2007;21(2):348-53. PMID 17530942.
- Antonio J, Uelmen J, Rodriguez R, Earnest C. "The effects of Tribulus terrestris on body composition and exercise performance in resistance-trained males." International Journal of Sport Nutrition and Exercise Metabolism, 2000;10(2):208-15. PMID 10861339.
- Qureshi A, Naughton DP, Petroczi A. "A systematic review on the herbal extract Tribulus terrestris and the roots of its putative aphrodisiac and performance-enhancing effect." Journal of Dietary Supplements, 2014;11(1):64-79. PMID 24559105.