Guanidinoacetic acid (Standard) is methylated in the liver to creatine and is involved in the regulation of energy metabolism that can be used as a standard for quantitative assays to study the creatine synthesis pathway, inherited metabolic disorders (e.g., guanidinoacetic acid methyltransferase deficiency), neurological disorders, and as a nutritional supplement to enhance athletic performance.Guanidinoacetic acid is a regulator of AMP-activated protein kinase (AMPK), can act as an inhibitor to down-regulate miR - 133a expression, and is an antagonist of the GABAC receptor.