Homovanillic acid-13C6,18O (Vanilacetic acid-13C6,18O) is the 13C- and 18O-labeled Homovanillic acid (HY-N0384). Homovanillic acid (Vanilacetic acid) is a dopamine metabolite found to be associated with aromatic L-amino acid decarboxylase deficiency, celiac disease, growth hormone deficiency, and sepiapterin reductase deficiency[1].