L-Citrulline is a neutral, non-essential α-amino acid and an important component of the urea cycle in the liver and kidneys. It is a rare non-protein amino acid in dietary sources, but it is found in relatively high levels in watermelon. In the body, L-Citrulline undergoes metabolic conversion in the kidneys to L-Arginine. Compared to oral L-Arginine, L-Citrulline effectively raises plasma levels of L-Arginine because it is transported to intestinal cells without being metabolically lost to arginase, bypasses hepatic metabolism, and is transported to the kidneys where it is converted to L-Arginine.