β-Hydroxyisovaleric Acid-d8 is the isotope labeled analog of β-Hydroxyisovaleric Acid; a metabolite of the essential amino acid Leucine. It is synthesized in the human body and studies suggest that β-Hydroxyisovaleric Acid may have an effect on increasing muscle weight and strength. The presence of elevated β-Hydroxyisovaleric Acid is a sensitive marker of biotin deficiency and may indicate the presence of a genetic disorder such as biotinidase deficiency or holocarboxylase synthetase deficiency.