L-arginine benefits: what the research does and doesn't show

The evidence doesn't support L-arginine as a treatment for erectile dysfunction, high blood pressure, or as a guaranteed exercise booster. What exists is a mixed research record: some meta-analyses report a real, measurable effect at specific doses, others find the trial quality too poor or inconsistent to draw a firm conclusion, and none of it describes what any particular product does.

What the evidence doesn't support

It doesn't support L-arginine as a treatment or cure for erectile dysfunction, hypertension, or heart disease, and nothing below should be read as a reason to use it in place of a doctor's evaluation or a prescribed treatment for any of those. It also doesn't support the idea that a specific milligram amount reliably produces a specific outcome — the trials below used a wide range of doses, several found effects only above certain thresholds, and heterogeneity (meaning the trials didn't agree well with each other) was flagged in more than one of the reviews. None of this research describes a particular product's effect; it describes what happened in specific trial populations, at specific doses, for a specific amount of time.

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 trials were small and used different doses and durations, so how large and how reliable that improvement is remains uncertain. The review's abstract doesn't specify which dose or duration of L-arginine drove this result, and the authors' overall framing was that most nutraceutical options for erectile dysfunction show limited effectiveness, with L-arginine among the few exceptions.

Blood pressure

The best-controlled data here is a 2022 dose-response meta-analysis of 22 randomized, placebo-controlled trials, which found L-arginine supplementation was associated with a mean decrease in systolic blood pressure of 6.40 mmHg and diastolic blood pressure of 2.64 mmHg compared with placebo, across trials lasting 4 or more days. The decrease showed up regardless of whether participants started with normal or high blood pressure, and regardless of sex, health status or body weight. A meta-regression in the same analysis linked a larger dose to a bigger diastolic change, and the authors identified 4 g/day as the smallest dose associated with a systolic effect in their non-linear modeling — but doses above 9 g/day showed no further significant change. An earlier 2016 umbrella review of 7 meta-analyses found a similar pattern — a 2.2 to 5.4 mmHg decrease in systolic and 2.7 to 3.1 mmHg in diastolic blood pressure among hypertensive adults, plus a 4.9 mmHg diastolic decrease in pregnant women with gestational hypertension, and a shorter hospital stay after surgery in 2 of 3 relevant meta-analyses — while explicitly flagging that 5 of the 7 meta-analyses it reviewed showed statistically significant heterogeneity, meaning the individual trials didn't agree well with each other. Both reviews describe a real, replicated pattern; both also come with real caveats about trial quality and consistency.

Exercise performance

A 2020 systematic review and meta-analysis pooled 15 trials comparing arginine supplementation with placebo on aerobic (at or below VO2max) and anaerobic (above VO2max) exercise performance. It found a statistically significant improvement in both aerobic performance (a large effect size, though with high heterogeneity — meaning wide disagreement between the pooled trials) and anaerobic performance (a small effect size, with low heterogeneity). Based on the trials it reviewed, the authors describe an acute protocol of 0.15 g per kg of body weight taken 60-90 minutes before exercise, and separately describe chronic protocols of 1.5-2 g/day for 4-7 weeks for aerobic performance or 10-12 g/day for 8 weeks for anaerobic performance — different doses and durations depending on which kind of performance is being measured, none of them small amounts.

Questions people ask

What are the benefits of L-arginine?

The most-studied findings are a measurable decrease in blood pressure in several meta-analyses, a statistically significant improvement in erectile function scores in a 2024 network meta-analysis, and an improvement in exercise performance in a 2020 meta-analysis — each at specific doses well above what a typical low-dose capsule provides, and each with real caveats about trial consistency that the summaries above spell out.

Does L-arginine help with ED?

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; the trials were small and varied in dose and length. It isn't a substitute for those medications or for a doctor's evaluation of erectile dysfunction.

Is L-arginine good for blood pressure?

Multiple meta-analyses report a measurable decrease in blood pressure with L-arginine supplementation, with one dose-response analysis identifying 4 g/day and up as the range associated with an effect, and no additional change reported above 9 g/day. This is a research finding about the ingredient in trials, not a treatment claim, and it isn't a substitute for prescribed blood pressure medication or a doctor's care.

Does L-arginine increase size?

We found no trial testing L-arginine for that specific outcome. The erectile-function research above measured standardized function scores in men already diagnosed with erectile dysfunction, which is a different question.

Is L-arginine good for the heart?

The clearest heart-related finding above is the blood pressure research. We haven't found the same strength of trial evidence directly tying L-arginine supplementation to heart disease outcomes (heart attack, stroke) themselves, as opposed to a blood pressure number, and it is not a treatment for heart disease.

What does L-arginine do for the body, generally?

Outside the specific outcomes above, L-arginine's basic biochemistry — what it is and how the body processes it — is covered separately; see what is L-arginine for that rather than this research summary.

When to talk to a doctor

L-arginine is not a treatment for erectile dysfunction, high blood pressure, or heart disease, and none of the research above should be used as a reason to delay a doctor's evaluation or to adjust a prescribed medication. If you have diagnosed erectile dysfunction, hypertension, or heart disease, or if you take medication for any of those, talk to your doctor before adding L-arginine — see L-arginine and medications: what to check and who should not take L-arginine for specifics.

Related reading: how much L-arginine should you take a day, what is L-arginine, and how to choose a good L-arginine supplement.