L-Alanine-d3 is intended for use as an internal standard for the quantification of L-alanine by GC- or LC-MS. L-Alanine is a non-essential amino acid. It is produced by direct β-decarboxylation of L-aspartate by L-aspartate β-decarboxylase or transamination of pyruvate in the glucose-alanine cycle and is a precursor for gluconeogenesis. Dysregulation of L-alanine metabolism is associated with various disease states, including diabetes, metabolic syndrome, ketotic hypoglycemia, and acquired acute lactic acidosis.