What the evidence says. Graded moderate: meta-analyses consistently show real but modest blood-pressure reductions and benefit in erectile dysfunction, but performance and endothelial effects are heterogeneous and often null, and most trials are small and short. (Moderate evidence: Several controlled trials; effects real but modest or context-dependent.)
What is L-Arginine?
L-Arginine is a performance supplement used for lower blood pressure. NutriDex grades the human evidence as Moderate. L-arginine is a conditionally essential amino acid and the body's substrate for making nitric oxide, a vasodilator. Pooled meta-analyses of randomized trials show oral arginine (4–24 g/day) lowers systolic blood pressure by roughly 5–6 mmHg and diastolic by about 2–3 mmHg versus placebo — modest but real. In erectile dysfunction, doses of 1.5–5 g/day, especially combined with pycnogenol, improve IIEF scores meaningfully in small trials. Effects on flow-mediated dilation are inconsistent and mostly non-significant once outliers are removed. For exercise, arginine shows a large but highly heterogeneous and publication-biased aerobic effect and only a small anaerobic one, so sports-nutrition bodies do not endorse it as a proven ergogenic aid. In pregnancy, arginine may reduce pre-eclampsia risk, though evidence is low-certainty. Overall, benefits are genuine but modest, and trials are largely small and short.
Purported Benefits
✓Lower blood pressure
✓Support blood-vessel function
✓Help erectile dysfunction (often with pycnogenol)
✓Possible aerobic performance edge
Evidence by outcome
The same supplement can be well-proven for one use and unproven for another — here is the human evidence graded outcome by outcome.
Outcome
Evidence
Effect
Studies
Lower blood pressureTwo meta-analyses (11 and 22 RCTs) agree on ~5-6 mmHg systolic / ~2-3 mmHg diastolic reduction.
Enhance aerobic exercise performanceLarge but highly heterogeneous, publication-biased aerobic effect (I²89%); small anaerobic effect. Not endorsed as ergogenic.
Mixed
↔ mixed
1
Reduce pre-eclampsia riskPrevention-trial meta-analysis found reduced pre-eclampsia risk (RR 0.52), but rated low-certainty.
Preliminary
↑ benefit · moderate
1
Dosing & Compounds
Typical Dose
Typically 4–6 g/day (up to 24 g/day in BP trials), split; ~10 g taken 60–90 min pre-exercise for performance.
Active Compounds
L-arginine (free amino acid)
Safety & Cautions
⚠
Generally well tolerated; high doses (>9 g/day) commonly cause GI upset, bloating and diarrhea. Because it lowers blood pressure and dilates vessels, it can add to antihypertensives, nitrates and PDE5 inhibitors (e.g. sildenafil), risking hypotension. Caution after a recent heart attack — a trial in post-MI patients found increased mortality with added arginine. May lower blood sugar (additive with antidiabetic drugs) and can worsen herpes outbreaks in susceptible people; avoid combining with blood thinners or other vasodilators without medical advice. Educational only — always check with your doctor or pharmacist before combining L-Arginine with any medicine.
L-Arginine drug interactions
Known or theoretical interactions between L-Arginine and common medications — educational, not exhaustive. Always check with your doctor or pharmacist before combining L-Arginine with any medicine.
L-Arginine is most often taken for Lower blood pressure, Support blood-vessel function, Help erectile dysfunction (often with pycnogenol), Possible aerobic performance edge. Nitric-oxide amino acid that modestly lowers blood pressure.
Does L-Arginine work — what does the evidence say?
Moderate evidence. Several controlled trials; effects real but modest or context-dependent. L-arginine is a conditionally essential amino acid and the body's substrate for making nitric oxide, a vasodilator. Pooled meta-analyses of randomized trials show oral arginine (4–24 g/day) lowers systolic blood pressure by roughly 5–6 mmHg and diastolic by about 2–3 mmHg versus placebo — modest but real. In erectile dysfunction, doses of 1.5–5 g/day, especially combined with pycnogenol, improve IIEF scores meaningfully in small trials. Effects on flow-mediated dilation are inconsistent and mostly non-significant once outliers are removed. For exercise, arginine shows a large but highly heterogeneous and publication-biased aerobic effect and only a small anaerobic one, so sports-nutrition bodies do not endorse it as a proven ergogenic aid. In pregnancy, arginine may reduce pre-eclampsia risk, though evidence is low-certainty. Overall, benefits are genuine but modest, and trials are largely small and short.
What is the typical dose of L-Arginine?
Typically 4–6 g/day (up to 24 g/day in BP trials), split; ~10 g taken 60–90 min pre-exercise for performance.
Is L-Arginine safe? Any cautions or side effects?
Generally well tolerated; high doses (>9 g/day) commonly cause GI upset, bloating and diarrhea. Because it lowers blood pressure and dilates vessels, it can add to antihypertensives, nitrates and PDE5 inhibitors (e.g. sildenafil), risking hypotension. Caution after a recent heart attack — a trial in post-MI patients found increased mortality with added arginine. May lower blood sugar (additive with antidiabetic drugs) and can worsen herpes outbreaks in susceptible people; avoid combining with blood thinners or other vasodilators without medical advice.
How many studies support L-Arginine?
NutriDex cites 8 sources for L-Arginine, graded "Moderate".
Does L-Arginine interact with any medications?
Yes — known or theoretical interactions include: Blood-pressure drugs (caution), Nitrates & ED drugs (PDE5 inhibitors) (caution). This is educational and not exhaustive; always check with your doctor or pharmacist before combining L-Arginine with any medicine.
Cite this page
APA
Peh, D. (2026). L-Arginine: Benefits, Dosage, Side Effects & Evidence. NutriDex — The Supplement Research Compendium. Retrieved 16 Sept 2026, from https://nutridex.info/s/l-arginine
BibTeX
@misc{nutridex_l_arginine,
author = {Peh, Daryl},
title = {L-Arginine: Benefits, Dosage, Side Effects \& Evidence},
year = {2026},
howpublished = {NutriDex --- The Supplement Research Compendium},
url = {https://nutridex.info/s/l-arginine},
note = {Reviewed by Dr Daryl Peh, MBBS Singapore, MMed FM. Accessed 2026-09-16}
}
For medical claims, citing the underlying primary studies linked above is preferred. NutriDex is an educational reference, not medical advice.