L-Arginine
Commonly used for
Heart HealthAthletic Performance
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Wellness uses
Erectile function support
This is anecdotal, and there isn't strong clinical evidence that it works for everyone.
What is it? / Overview
L-Arginine is the direct precursor to nitric oxide, a molecule that promotes vasodilation. Supplementation can improve endothelial function and may help mild erectile dysfunction, but oral citrulline generally produces larger and more sustained increases in arginine levels, making it the preferred supplement for most performance and vascular applications.
How is it used? / Administration
Form: L-Arginine free-form powder or capsules
Typical dose studied: 3–8 g/day (up to 10 g/day in some studies)
Timing: 30–60 min before exercise or between meals
L-Citrulline is generally superior for nitric oxide production because it bypasses first-pass metabolism. L-Arginine remains useful for specific clinical applications like erectile dysfunction. Arginine alpha-ketoglutarate (AAKG, arginine bound to alpha-ketoglutarate) is a common pre-workout "pump" form — controlled trials found AAKG raised plasma arginine but produced no independent blood-flow or nitric-oxide benefit beyond exercise itself, so it has no demonstrated advantage over plain L-arginine and the same contraindications above apply to it.
How well does it work? / Evidence
~ Moderate evidence
Who should avoid it?
Avoid with: Chronic coronary disease / Coronary artery disease; Heart failure / Congestive heart failure
Interacts with: PDE-5 inhibitors — monitor blood pressure; Nitrates; Antihypertensive medications
Already taking it? Citrulline is generally preferred due to superior pharmacokinetics for the same purpose. Avoid specifically in the post-MI setting: the VINTAGE MI trial found L-arginine added to standard post-heart-attack therapy did not improve vascular stiffness or ejection fraction and was associated with higher post-infarction mortality, and the AHA's complementary/alternative medicine scientific statement recommends against L-arginine use after acute MI. Theoretical, minor caution: may promote herpes simplex viral replication in someone with an active outbreak.
Research & references
Rhim HC et al. (2019). L-arginine and erectile dysfunction systematic review. World Journal of Men's Health. Alvares TS et al. (2011). L-arginine as ergogenic aid review. Sports Medicine. Maughan RJ et al. (2018). IOC consensus statement: dietary supplements and the high-performance athlete. Br J Sports Med. Schulman SP et al. (2006). L-arginine therapy in acute myocardial infarction: the Vascular Interaction With Age in Myocardial Infarction (VINTAGE MI) randomized clinical trial. JAMA. Vogel JHK et al. (2005). Integrating complementary medicine into cardiovascular medicine. ACC Foundation task force / AHA scientific statement on complementary and alternative medicine.
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