NutriDex

The Supplement Research Compendium
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L-Arginine

Nitric-oxide amino acid that modestly lowers blood pressure.

Moderate evidence ⚡Performance🫀Heart & Metabolic

✚ Updated · How we grade evidence

Evidence tier
Moderate
Research weight
Citations
6 verified / 6
Classification
Performance
❝
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.

OutcomeEvidenceEffectStudies
Lower blood pressureTwo meta-analyses (11 and 22 RCTs) agree on ~5-6 mmHg systolic / ~2-3 mmHg diastolic reduction. Strong ↑ benefit · small 2
Improve erectile dysfunction (with pycnogenol)3-RCT meta-analysis: arginine+pycnogenol improved IIEF by ~8.9 points, but trials small and combination-dependent. Moderate ↑ benefit · moderate 1
Improve endothelial function (flow-mediated dilation)8-RCT meta-analysis found no significant effect on flow-mediated dilation once heterogeneity considered. Moderate — no effect · negligible 1
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.

Caution
Blood-pressure drugs
L-arginine can lower blood pressure and may add to antihypertensive drugs, risking hypotension.
L-arginine is a nitric oxide precursor that promotes vasodilation, compounding blood-pressure drugs. L-arginine potentiates pulmonary vasodilation (PubMed)
Caution
Nitrates & ED drugs (PDE5 inhibitors)
L-arginine with nitrates or ED drugs (sildenafil, tadalafil) may cause an additive drop in blood pressure.
L-arginine raises nitric oxide and cGMP-driven vasodilation, adding to nitrates and PDE5 inhibitors. Sildenafil-induced hypotension and nitrates (PubMed)

Key Studies

Meta-analysis Rhaman 2023 ✓ PubMed
Meta-analysis (3 RCTs, 184 men): L-arginine plus pycnogenol improved IIEF erectile score by 8.9 points vs placebo.
Meta-analysis Makama 2025 ✓ PubMed
Meta-analysis: in prevention trials L-arginine cut pre-eclampsia risk (RR 0.52) and severe pre-eclampsia (RR 0.23); low-certainty.
Meta-analysis Mahdavi 2022 ✓ PubMed
Dose-response meta-analysis (22 RCTs): L-arginine reduced systolic BP by 6.40 mmHg and diastolic by 2.64 mmHg.
Meta-analysis Viribay 2020 ✓ PubMed
Meta-analysis (18 studies): large but heterogeneous aerobic effect (ES 0.84, I²=89%); small anaerobic effect (ES 0.24).
Meta-analysis Rodrigues-Krause 2018 ✓ PubMed
Meta-analysis (8 RCTs, n=469): no significant effect of L-arginine on flow-mediated dilation (SMD 0.30, CI -0.85 to 1.46).
Meta-analysis Dong 2011 ✓ PubMed
Meta-analysis (11 RCTs, n=387): oral L-arginine lowered systolic BP 5.39 mmHg and diastolic 2.66 mmHg vs placebo.
6 sources cited · 6 verified Search all studies on PubMed ↗

Common questions about L-Arginine

What is L-Arginine used for?

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 6 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 26 Jun 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 2026-06-26}
}

For medical claims, citing the underlying primary studies linked above is preferred. NutriDex is an educational reference, not medical advice.

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