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What is L-arginine?

Eggs, meats, milk, soy proteins, peanuts, and walnuts are all sources of arginine. The physiologically active form, L-arginine, is obtained by breaking down proteins. Arginine also may be synthesized in the laboratory. Because L-arginine may be synthesized in the body, it is classified as a nonessential amino acid in adults. However, in children and in people with certain conditions (eg, infection, trauma), L-arginine synthesis may become compromised and then may be considered semi-essential.

What is it used for?

Traditional/Ethnobotanical uses

L-arginine is a nonessential amino acid that may play an important role in the treatment of heart disease due to its block arterial plaque buildup, blood clots, platelet clumping, and to increase blood flow through the coronary artery. L-arginine is commonly sold as a health supplement claiming to improve vascular health and treat erectile dysfunction in men. L-arginine, which is promoted as a human growth stimulant, has also been used in bodybuilding. In the 1800s, it was first isolated from animal horn.

What is the recommended dosage?

L-arginine has been studied at oral doses of 6 to 30 g/day for a variety of conditions. Many formulations have been used.


Absolute contraindications have not been identified. L-arginine is not recommended in patients following an acute heart attack.


Specific information regarding safety and efficacy during pregnancy and breast-feeding is lacking, although several trials have been conducted in pregnant women without notable ill effects.


L-arginine has unpredictable effects on insulin and cholesterol-lowering agents. L-arginine may increase the effects of isosorbide mononitrate and other nitric oxide donors, such as glyceryl trinitrate and sodium nitroprusside.

Side Effects

L-arginine has few reported adverse reactions. Nausea and diarrhea have been reported infrequently. Bitter taste may occur with higher doses. Due to its ability to dilate blood vessels, low blood pressure may occur. Intravenous preparations containing L-arginine hydrochloride have a high chloride content that may increase the risk for metabolic acidosis in patients with electrolyte imbalances. Low potassium and high serum urea nitrogen levels may occur in patients with kidney and/or liver impairment.


High concentrations of nitric oxide, which can be produced by L-arginine, are considered toxic to brain tissue.


1. L-arginine. Review of Natural Products. Facts & Comparisons [database online]. St. Louis, MO: Wolters Kluwer Health Inc; October 2010.

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