Does L-arginine raise testosterone? What the research does and doesn't show

The evidence doesn't support L-arginine as a reliable way to raise testosterone. One trial found testosterone rose in male bodybuilders taking L-arginine plus vitamin C alongside a structured training program — a combination that can't isolate arginine's own effect. A separate trial testing a single dose of arginine alone found no significant testosterone change. The more consistent finding in this general area is for erectile function scores, not testosterone itself.

What the evidence doesn't support

It doesn't support L-arginine as a testosterone-boosting supplement on its own — the one trial that found a testosterone increase combined it with vitamin C and a supervised exercise program, so the result can't be attributed to arginine alone. 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 addresses. And it doesn't support extending the erectile-function-score findings below to testosterone, libido, or sperm-related outcomes — they're separate measurements from separate trials.

What the trials found

Testosterone

A 45-day randomized, double-blind, placebo-controlled 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 resistance-and-aerobic training program. The supplement group had a significant increase in serum testosterone and VO2max, and a significant decrease in body weight, BMI and body fat, compared with placebo. Growth hormone and cortisol didn't differ significantly between groups. Because the intervention combined arginine, vitamin C and supervised training, this trial can't isolate what arginine contributed on its own, and the population — competitive male bodybuilders on a structured program — isn't a general population.

A separate, differently designed trial found the opposite result for testosterone specifically. Thirty healthy, physically active men took a single 10 g dose of arginine (or placebo) in a crossover design, with blood drawn out to 24 hours. Growth hormone rose significantly (193% at 24 hours) and glucose rose modestly, but testosterone was not among the measures that changed significantly. This was a single acute dose, not a chronic-use trial, so it doesn't rule out an effect from sustained daily use — but it's a direct, controlled test of arginine alone, and it didn't find a testosterone change.

Taken together, the honest summary is that the one trial reporting a testosterone increase used a multi-ingredient, multi-intervention design that can't isolate arginine, while the one trial that isolated arginine alone found no significant testosterone change at a single dose.

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 the review's abstract doesn't specify which dose drove the result. Erectile function score is a different measurement from a testosterone level — this finding doesn't imply anything about testosterone one way or the other.

Libido and sperm volume

We haven't found a dedicated, placebo-controlled trial that isolated L-arginine alone and measured self-reported libido, or semen volume, in a general population. That's a real gap in the record, not a finding either way — it means these specific, commonly searched questions don't have a direct trial answer yet.

Outcome	Best evidence	Population / design	Result
Testosterone (combined intervention)	1 RCT	50 male bodybuilders, 45 days, arginine + vitamin C + training	Increased vs placebo — can't isolate arginine
Testosterone (arginine alone)	1 RCT	30 healthy men, single 10 g dose	No significant change
Erectile function score	Meta-analysis, 15 RCTs	1,000 men with erectile dysfunction	Improved vs placebo
Libido / sperm volume	None found	—	No dedicated trial identified

Questions people ask

Does L-arginine increase testosterone?

The record is mixed and thin. One combined-intervention trial (arginine, vitamin C and structured training together) found testosterone rose in male bodybuilders. A separate trial isolating a single dose of arginine alone found no significant testosterone change. There isn't a clean, isolated trial showing arginine alone reliably raises testosterone.

Does L-arginine increase libido or sperm volume?

No dedicated trial measuring either outcome with L-arginine alone was found for this review. That's an honest gap, not a negative result — these specific outcomes simply haven't been tested directly.

Will L-arginine help with erectile dysfunction?

A 2024 network meta-analysis of 15 trials in 1,000 men found L-arginine alone was associated with a statistically significant improvement in erectile function scores versus placebo. It isn't a substitute for a doctor's evaluation of erectile dysfunction, and the pooled trials were small and varied in dose and length.

How much L-arginine should I take for sexual health, and when?

The erectile-function meta-analysis above doesn't specify a dose or timing across its pooled trials, so there isn't a research-backed number to give here. General L-arginine dosing research (blood pressure, exercise) used doses from roughly 1.5 g/day to over 9 g/day depending on outcome — see L-arginine dosage — but none of that research measured a sexual-health outcome specifically.

When to talk to a doctor

L-arginine is not a treatment for low testosterone, erectile dysfunction, or male infertility. Persistent changes in libido, erectile function or fertility are worth evaluating with a doctor, who can check for underlying causes a supplement search won't identify. If you take medication, particularly for blood pressure or erectile dysfunction, talk to a doctor before adding L-arginine — see L-arginine and medications: what to check.

Related reading: L-arginine benefits: what the research does and doesn't show, what does L-arginine do for men, and what is L-arginine.