What does L-arginine do for men? What the research does and doesn't show

Most of L-arginine's best-studied outcomes — erectile function, exercise performance, blood pressure — come from all-male or male-skewed trial samples, so there's more to say here than on a general or female-specific page. Erectile function scores have the most consistent trial support; testosterone and fertility-adjacent evidence is thinner and more mixed.

What the evidence doesn't support

It doesn't support L-arginine as a treatment for erectile dysfunction, low testosterone, or male infertility — those are diagnoses for a doctor, not outcomes a supplement search resolves. It doesn't support the idea that L-arginine reliably raises testosterone; the one trial reporting an increase combined it with vitamin C and supervised training, and a separate trial isolating arginine alone found no significant testosterone change. And it doesn't support carrying any of the doses below over to a general "good for men" recommendation — each trial used its own dose for its own specific outcome.

What the trials found

Erectile function

A 2024 systematic review and network meta-analysis pooled 15 randomized, placebo-controlled trials in 1,000 men with erectile dysfunction. Compared with placebo, L-arginine on its own was associated with a statistically significant improvement in erectile function scores. The pooled trials were small and varied in dose and duration, and this isn't a substitute for a doctor's evaluation of erectile dysfunction — see does L-arginine raise testosterone for the full breakdown of this and related findings.

Exercise performance

A 2020 meta-analysis of 15 studies, predominantly in male or male-majority samples, found a statistically significant improvement in both aerobic performance (large effect, high inconsistency between trials) and anaerobic performance (small effect, low inconsistency between trials). The doses used ranged from 0.15 g/kg body weight taken 60-90 minutes pre-exercise (acute) to 1.5-12 g/day over 4-8 weeks (chronic), depending on which type of performance was measured.

Testosterone: mixed, thin evidence

A 45-day randomized trial gave 50 male bodybuilders either 3,000 mg/day L-arginine plus 500 mg/day vitamin C, or placebo, while everyone followed the same structured training program. Testosterone rose significantly in the supplement group — but the intervention combined three things (arginine, vitamin C, supervised training), so the result can't be attributed to arginine on its own. A separate, differently designed trial gave 30 healthy men a single 10 g dose of arginine alone and found growth hormone rose significantly, while testosterone was not among the measures that changed. The honest summary: the trial that isolated arginine alone found no testosterone effect; the trial that found an effect didn't isolate arginine.

Libido and fertility-adjacent outcomes: a gap, not a finding

We haven't found a dedicated, placebo-controlled trial isolating L-arginine alone and measuring self-reported libido or semen-quality outcomes in men. That's a real gap in the record — these specific, often-searched questions don't have a direct trial answer yet, one way or the other.

Questions people ask

What does L-arginine do for men, and what's it good for?

Based on the trial evidence: a documented improvement in erectile function scores in men with erectile dysfunction, an improvement in exercise performance at gram-level doses, and a mixed, unresolved record on testosterone. See L-arginine benefits: what the research does and doesn't show for the underlying findings and their limits.

How much L-arginine per day for men?

There's no single dose that applies across every outcome — the exercise research used 1.5-12 g/day depending on what was measured, the blood pressure research identified roughly 4 g/day and up, and the erectile-function meta-analysis didn't specify a dose. See L-arginine dosage for the full breakdown by outcome.

Which L-arginine is best for men?

This page doesn't recommend a specific brand or product. Whatever you're comparing, check the form (plain L-arginine vs. L-arginine HCl), the dose per serving against the research above, and how it's tested — see how to choose a good L-arginine.

How much L-arginine for male fertility?

No dedicated, placebo-controlled trial testing L-arginine's effect on male fertility outcomes was found for this review, so there's no dose to report here. Fertility concerns are worth raising with a doctor for proper evaluation rather than addressing with a supplement dose pulled from unrelated research.

When to talk to a doctor

L-arginine is not a treatment for erectile dysfunction, low testosterone, or male infertility. If you have any of those diagnosed, or take medication — especially for blood pressure or erectile dysfunction — talk to a doctor before adding L-arginine. See L-arginine and medications: what to check and who should not take L-arginine.

Related reading: does L-arginine raise testosterone, L-arginine benefits, and L-arginine dosage.