Research review
What does L-citrulline do for men? What the research does and doesn't show
L-citrulline is marketed toward men mainly because most of its research recruited men, not because of a male-specific mechanism. That research found a small exercise-performance benefit, improved erection hardness in one small trial of men with mild erectile difficulty, and no testosterone change in the one trial that measured it.
Most of L-citrulline's exercise-performance and erectile-function research happens to have been done in men, which is why the ingredient gets marketed toward men specifically — not because of anything male-specific in how it works. What that male-heavy research base actually found: a small exercise-performance benefit, improved erection hardness in one small trial of men with mild erectile difficulty, and no change in testosterone in the one trial that measured it.
What the evidence doesn't support
It doesn't support L-citrulline as a testosterone booster — the one trial that measured testosterone directly, in young male athletes, found no significant change. It doesn't support L-citrulline as a treatment for erectile dysfunction as a diagnosed condition, or a substitute for prescription treatment — the one positive erectile-function trial's own authors describe citrulline as less effective than standard PDE-5 inhibitor medication. And it doesn't support a male-specific mechanism behind any of citrulline's research: the nitric-oxide pathway it works through operates the same way in men and women, so a study population being mostly men reflects who researchers happened to recruit, not a male-only effect.
What the trials found
A 2019 meta-analysis pooled 12 studies (198 participants, predominantly men) testing a single citrulline dose — at least 3 g, given 30 or more minutes before high-intensity strength or power exercise — against placebo. The pooled result favored citrulline by a small but statistically significant margin (standardized mean difference 0.20, 95% CI 0.01-0.39, p=0.036); every individual study's own confidence interval still crossed the line of no effect.
A 2010 randomized, crossover trial gave 41 men a single 8 g dose of citrulline malate or placebo before a bench-press training session. Repetitions completed increased significantly from the third set onward with citrulline malate, reaching 53% more repetitions than placebo by the final set, and muscle soreness 24 and 48 hours later was about 40% lower. About 15% of participants reported stomach discomfort.
A 2025 randomized, double-blind trial gave 33 resistance-trained men 8 g/day of plain L-citrulline, 12 g/day of citrulline DL-malate, or placebo, alongside 6 weeks of resistance training. Upper-body muscular endurance improved significantly more in both citrulline groups than placebo, with no meaningful difference between the two forms.
A 2011 single-blind, sequential trial gave 24 men (mean age 56.5) with mild erectile dysfunction a placebo for one month and 1.5 g/day of L-citrulline for a second month. Erection-hardness score improved from mild dysfunction to normal function in 50% of men on citrulline, versus 8.3% on placebo (p<0.01). Monthly intercourse frequency rose from about 1.4 to 2.3. The trial's own authors call citrulline less effective than PDE-5 inhibitor medication and suggest it as an option specifically for men reluctant to use that medication, not a replacement for it.
A 2025 randomized, controlled trial gave 40 young male basketball players either L-citrulline (6 g/day), sodium bicarbonate, both combined, placebo, or an active control, alongside 4 weeks of sprint-interval training. Physical performance improved more in every supplemented group than placebo. Resting testosterone did not change significantly in any group, though the supplemented groups showed lower cortisol than the others.
Why the research skews male
Sports-supplement and urology research has historically recruited men more than women for practical and funding reasons, not because citrulline's mechanism is male-specific — it converts to arginine and feeds nitric-oxide production in blood vessels the same way regardless of sex. That's the honest explanation for why "L-citrulline for men" returns more research than "L-citrulline for women": the studies exist, not that the effect does.
Questions people ask
What does L-citrulline do for men?
In the trials above: a small improvement in high-intensity exercise performance and muscular endurance, and improved erection hardness in men with mild erectile dysfunction in one small trial. Testosterone didn't change in the one trial that measured it.
What does L-arginine and L-citrulline do for men?
We didn't find a trial testing that specific combination. The trials above tested L-citrulline (or citrulline malate) on its own; L-arginine appeared only combined with citrulline in a watermelon-extract blood-pressure trial, not as a men's-specific combination product.
Does L-citrulline increase testosterone in men?
The one trial that measured it directly — 6 g/day for 4 weeks in young male athletes — found no significant change.
Is L-citrulline good for men over 60?
The erectile-function trial above averaged 56.5 years old, and the exercise trials skewed younger. We didn't find a trial specifically testing men over 60, and no trial has run past 6 weeks of daily use at any age.
When to talk to a doctor
L-citrulline is not a treatment for low testosterone or erectile dysfunction, and nothing above should stand in for a doctor's evaluation of either. If erectile difficulty or a suspected hormonal issue is ongoing, or if you take a PDE-5 inhibitor, nitrate, or blood-pressure medication, talk to a doctor before adding L-citrulline.
Related reading: L-citrulline benefits: what the research does and doesn't show and does L-citrulline raise testosterone?.
Sources
- Acute Effects of Citrulline Supplementation on High-Intensity Strength and Power Performance: A Systematic Review and Meta-Analysis A 2019 meta-analysis pooling 12 studies (198 people) found a small but statistically significant benefit of a single citrulline dose (at least 3 g, taken 30+ minutes before exercise) on high-intensity strength and power performance, though every individual study's own result could still have been due to chance.
- Citrulline malate enhances athletic anaerobic performance and relieves muscle soreness A 2010 crossover trial in 41 men found a single 8 g dose of citrulline malate before a bench-press session increased the number of repetitions completed as the sets went on, and reduced next-day and two-day muscle soreness by about 40%, compared with placebo; about 15% of participants reported stomach discomfort.
- Changes in resistance training performance, rating of perceived exertion, and blood biomarkers after six weeks of supplementation with L-citrulline vs. L-citrulline DL-malate in resistance-trained men: a double-blind placebo-controlled trial A 2025 six-week trial in 33 resistance-trained men found that daily L-citrulline (8 g) or citrulline malate (12 g) improved upper-body muscular endurance more than placebo and raised a blood marker of nitric-oxide production, with no meaningful difference between the two citrulline forms on any measured outcome.
- Oral L-citrulline supplementation improves erection hardness in men with mild erectile dysfunction A 2011 single-blind trial in 24 men with mild erectile dysfunction found that 1.5 g/day of L-citrulline for a month improved erection hardness in half the men, versus about 8% during a placebo month, with no adverse events reported — the study's own authors describe it as less effective than standard PDE-5 inhibitor medication.
- Combined Vs. Single Supplementation of L-Citrulline and Sodium Bicarbonate During Sprint Interval Training in Basketball Players: Effects on Physical Performance and Hormonal Adaptations A 2025 trial in 40 young male basketball players found that 6 g/day of L-citrulline for 4 weeks, alongside sprint-interval training, improved physical performance more than placebo but did not significantly change resting testosterone; cortisol, a stress hormone, was lower in the supplemented groups.
*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.