Tribulus terrestris
Tribulus terrestris is a saponin-containing plant (standardised to protodioscin) marketed for decades as a testosterone booster. Despite its popularity, controlled human trials in healthy men consistently fail to show any meaningful rise in testosterone or muscle mass. There is weak evidence for a libido effect, likely independent of androgens.
01 Overview
Steroidal saponins such as protodioscin are claimed to raise luteinising hormone and testosterone, but this has not held up in humans: multiple RCTs in athletes and healthy men show no significant change in serum androgens or performance versus placebo. Its historical reputation rests largely on early animal studies and marketing rather than clinical data.
Some studies do report improved libido and erectile satisfaction, which may be a direct effect on nitric-oxide/sexual pathways rather than a hormonal one. Users take standardised extracts for libido and out of habit within 'test-booster' stacks. It is generally well tolerated but there are rare case reports of hepatotoxicity and, importantly, its saponins can cause athletes to fail testosterone/epitestosterone doping screens through contamination or metabolite interference.
02 Mechanism
Steroidal-saponin extract (protodioscin) claimed to raise LH and testosterone; human data do not support an androgenic mechanism, and any libido effect is likely via nitric-oxide/sexual pathways.
03 Dosing
| Tier | Dose | Route | Notes |
|---|---|---|---|
| Standardised extract | 250–750 mg/day | Oral | Commonly standardised to 40-60% saponins; often split. |
| Higher supplemental use | 750–1500 mg/day | Oral | Upper anecdotal range; no clear added hormonal benefit. |
04 Effects
| Effect | Magnitude | Evidence | |
|---|---|---|---|
| Possible libido improvementSome trials report better libido and erectile satisfaction, probably not via testosterone. | modest / subjective | Observational | |
| No meaningful testosterone increaseControlled trials repeatedly find no significant change in serum testosterone or performance in healthy men. | none in healthy men | Clinical |
05 Side effects
| Effect | Severity | Frequency | Evidence | Countermeasures |
|---|---|---|---|---|
| Doping-test interferenceTribulus use has been associated with altered testosterone/epitestosterone ratios and product contamination that can trigger positive doping screens. | Moderate | Athlete-relevant | Observational | |
| Gastrointestinal upsetStomach cramps and nausea, particularly on an empty stomach. | Mild | Common | Observational | |
| Rare hepatotoxicity / nephrotoxicityIsolated case reports describe liver and kidney injury associated with tribulus products. | Severe | Rare | Observational |