In Vitro: Malonylcarnitine and Glutarylcarnitine are important diagnostic metabolites in the screening of dried blood spots by tandem mass spectrometry. The urinary excretion of glutarylcarnitine is a specific biochemical marker of glutaric acidemia type I (GA-1). The urinary excretion of glutarylcarnitine is an informative tool in the biochemical diagnosis of glutaric acidemia type I.