L-citrulline, like L-arginine and L-ornithine, is involved in the metabolism of ammonia waste in the urea cycle, and in the vasodilation pathways.* Carbamoyl phosphate is converted to citrulline in the ornithine carbamoyltransferase reaction, and when endogenous supplies of ornithine carbamoyltransferase are insufficient, supplemental L-citrulline may be useful.* Free form amino acid, high purity, well tolerated.