L-Arginine

Arginine · L-Arg

Snapshot

Indications	Contraindications
Blood pressure lowering¹ Vasculogenic erectile dysfunction² Hypertensive disorders of pregnancy³ Fetal growth restriction⁴ Wound healing⁵ Radiation-induced oral mucositis⁶ Sickle cell disease⁷ Exercise capacity⁸	Prior myocardial infarction⁹ Glaucoma or herpes simplex¹⁰

L-arginine is a conditionally essential amino acid and the substrate for nitric oxide (NO) synthesis, which drives vasodilation and tissue blood flow¹¹. Supplementation follows from that effect: blood pressure lowering, vasculogenic erectile dysfunction, hypertensive disorders of pregnancy, wound healing, and exercise capacity¹¹.

For blood pressure, a meta-analysis of five small ambulatory-monitoring trials found oral l-arginine lowered 24-hour, daytime and nighttime blood pressure, though the authors note few studies were available¹². In pregnancy, meta-analyses found better birth outcomes in women with prior poor outcomes or hypertensive disorders^{3, 4}. Arginine-enriched enteral nutrition in critically ill patients did not reduce infection¹³. In adults with long coronavirus disease 2019 (COVID), a 2022 single-blind randomized trial of arginine plus vitamin C found better walking distance, grip strength, and fatigue than placebo¹⁴. Products listing L-arginine are on the market, mostly capsules and powders; see Form comparison.

Health Canada labeling contraindicates use after a heart attack⁹. Per Health Canada labeling, practitioner advice is sought before use with cardiovascular, erectile dysfunction, or blood-thinning medication⁹.

Last updated October 16, 2026. Read how we make monographs.

In the full monograph

79 sources, 63 studies

When to useThe situations practitioners use it for, each with the reason and the study behind it.
SafetyWho should avoid it, who needs extra care, and the side effects reported in studies.
InteractionsThe medicines and supplements it interacts with, the effect of each, and what labeling says to watch.
Protocol notesThe doses used in studies, how and when they were taken, and how the forms on the market compare.
How it worksWhat it is and how it works in the body, in plain terms.
Published studiesThe studies behind each use, popular claims checked against them, and trials still under way.
Word of mouthWhat patients and practitioners report online, kept separate from the clinical evidence.
Clinical perspectiveA closing read of where the evidence is solid, where it is thin, and what has not been studied.

Snapshot

In the full monograph

Sources