Tribulus Terrestris for Erectile Dysfunction

Tribulus terrestris may give a small improvement in erectile dysfunction, but the trials disagree. A 2026 meta-analysis of eight studies found that, against placebo, Tribulus raised scores on the IIEF-5 erection questionnaire by a mean of 3.23 points (95% CI 1.89 to 4.58), with no difference in testosterone or in side effects [1]. The largest trial, of 180 men with mild to moderate ED, found a 2.70-point gain over placebo on the IIEF after 12 weeks [2].

The rest of the evidence is less encouraging. A 30-man trial of 800 mg a day for 30 days found no difference from placebo [3]. A 2025 systematic review judged half its studies low quality and rated the evidence for ED low [4], and a 2026 meta-analysis of 14 herbal trials called the Tribulus evidence insufficient [5]. Proven treatments exist: every PDE5 inhibitor beat placebo across 179 randomised trials [6], and the American Urological Association asks clinicians to discuss all suitable options with each man [7].

Tribulus is marketed for testosterone, but that claim has not held up in people. In 21 healthy young men, 4 weeks of 10 or 20 mg per kg of body weight a day left testosterone, androstenedione and luteinising hormone no different from placebo [8]. In men with ED, the 2026 meta-analysis found no difference in total testosterone between Tribulus and placebo [1], and a 2024 systematic review of testosterone boosters, which included four Tribulus studies, found most products fail to raise testosterone [9]. NIH's LiverTox notes that hormonal effects seen in animals have not been reproduced consistently in humans [10].

The main active compounds are thought to be steroidal saponins such as protodioscin [11]. A 2016 review concluded the androgen explanation was wrong and pointed to animal studies suggesting Tribulus acts on the lining of blood vessels and on nitric oxide, the signal that relaxes penile tissue so it can fill with blood [12].

The nitric oxide evidence comes from animals, and no study has shown it in men with ED [12]. Small testosterone rises (60-70 ng/dL, of low clinical magnitude) were seen only within the Tribulus groups of men with low testosterone, not against placebo [4]. So even when erection scores improve, we don't know why, which also makes it hard to know which extract or dose matters for erectile function.

The largest positive trial used a Bulgarian extract standardised to furostanol saponins: two 250 mg tablets three times a day after meals, so 1,500 mg of extract a day, for 12 weeks [2]. An uncontrolled pilot in older men with low testosterone used 750 mg a day in three doses for 3 months [13]. The trial that found no benefit used 800 mg a day, split into two doses, for only 30 days [3].

Across the studies in a 2025 review, doses ran from 400 to 750 mg a day for 1 to 3 months [4]. LiverTox lists the usual daily dose as 250 to 750 mg, so the 1,500 mg used in the largest trial is twice the top of that range; it warns that high doses may be harmful, particularly in people with liver disease or cirrhosis, and notes that Tribulus also turns up in many multi-ingredient products sold for sexual problems [10]. An analysis of 25 ED supplements sold in Italy found 80% had no expected efficacy; most were blends with ingredients at negligible doses or without evidence [14].

The strongest single trial randomised 180 men aged 18-65 with mild or moderate ED, including men with high blood pressure, diabetes or metabolic syndrome, to the standardised extract or placebo for 12 weeks; 86 in each group finished. IIEF scores improved more on Tribulus (difference 2.70, 95% CI 1.40 to 4.01, P < 0.0001), as did intercourse satisfaction, orgasm, desire and overall satisfaction, with no difference in side effects [2].

A smaller double-blind trial gave 30 men aged 40 and over 800 mg a day or placebo for 30 days. IIEF-5 rose from 13.2 to 15.3 on Tribulus and from 11.6 to 13.7 on placebo, with no difference between groups (P = .79), and testosterone did not change [3]. In 70 older men with partial androgen deficiency, ED and urinary symptoms, the abstract reports IIEF-5 rising from 10.7 to 16.1 over 3 months on Tribulus, but gives no direct comparison with the placebo group [11]. An uncontrolled pilot in 30 similar men reported higher testosterone and IIEF-5 scores after 3 months [13].

The 2026 meta-analysis pooled eight studies and found Tribulus beat placebo on both the IIEF-5 (mean difference 3.23) and the longer IIEF-15 (14.44), with no change in testosterone and no excess of side effects [1]. A 2023 meta-analysis also listed Tribulus with ginseng and L-arginine among the supplements able to improve male sexual function [14].

Other reviews are cooler. A 2018 meta-analysis of herbal ED treatments found two Tribulus trials (202 men) with mixed results [16]. A 2025 systematic review of 10 studies (483 men) found Tribulus improved ED in 3 of the 5 studies that measured it, rated half the studies low quality, and concluded the evidence was low [4]. A 2026 meta-analysis of 14 herbal trials (1,227 men) judged the Tribulus evidence insufficient [5], and a 2026 synthesis for French urology societies named ginseng, L-arginine and pine bark as the only modest signals, and found the evidence does not support routinely recommending herbal treatments [17].

The trials were small and short, used different extracts and doses, and measured outcomes in different ways. For better-studied supplements, see Korean ginseng for ED and L-arginine for ED; the evidence for maca and pine bark extract is also preliminary.

Many products combine Tribulus with other ingredients, which hides its own effect. In a single-blind trial of 177 men with mild to moderate ED, a blend of the alga Ecklonia bicyclis, Tribulus and glucosamine oligosaccharide improved IIEF-15 scores by a mean of 11.54 points more than placebo after 3 months [18]. In 98 men given a tablet of protodioscin, ginseng extract and L-arginine for 3 months, IIEF-5 scores improved in men without diabetes but not in men with diabetes compared with placebo [19]. Neither trial can say how much came from Tribulus, and products with ginseng or L-arginine owe some of their effect to those ingredients.

In the trials, side effects were no more common than on placebo: in the 2026 meta-analysis [1], in the 180-man trial, which reported no drug-related serious adverse events [2], and across herbal ED trials in a 2018 review [16]. LiverTox describes Tribulus as well tolerated but possibly linked to mild stomach discomfort, nausea or indigestion [10]. In the 3-month trial in older men, the liver enzyme AST and PSA, a prostate blood marker, rose slightly but significantly on Tribulus, while urinary symptoms did not worsen [11].

The plant itself causes serious liver injury in grazing animals. LiverTox says Tribulus extracts at typical doses have not been convincingly linked to liver injury in humans, but that high doses should be considered potentially harmful, particularly in people with liver disease or cirrhosis [10]. Rare case reports describe a 36-year-old man with priapism lasting 72 hours after taking a Tribulus supplement, who needed surgery and had worse sexual function afterwards [20], and a 71-year-old man on long-term atorvastatin who developed rhabdomyolysis, a dangerous breakdown of muscle, after adding Tribulus [21]. None of the trials lasted more than 3 months.

The clearest warning comes from a case report: a man taking atorvastatin developed rhabdomyolysis with mild liver inflammation after starting Tribulus. Its authors cite research suggesting Tribulus is a moderate inhibitor of CYP3A4, the liver enzyme that clears many statins and other common medicines [21]. This rests on one case, but it is reason to check with your prescriber if you take a statin or other CYP3A4-cleared drugs.

No trial tested Tribulus with PDE5 inhibitors such as sildenafil or tadalafil; a 2024 network meta-analysis of nutraceutical ED trials found only L-arginine and a carnitine mixture of some use, mainly alongside these drugs [22]. Because Tribulus raised PSA slightly in one trial [11], tell your doctor if you are having PSA tests.