Background: Accumulation of 3-hydroxyglutaric acid (3HGA) in body fluids is pathognomonic for type 1 Glutaric Aciduria (GA1). To date, methods for quantification of 3HGA mainly involve complex analyses using stable isotope dilution gas chromatography mass spectrometry (GC-MS). Here, we describe a simple liquid chromatography tandem mass spectrometry (LC-MS/MS) method to quantify 3HGA in dried urine spots (DUS) using DAABD-AE, a benzoxadiazole-type reagent designed for improving chromatographic and mass spectrometric properties of carboxylic acids. Material and Methods: No extraction was required and derivatization was performed directly on a 3.2-mm disc of DUS. Sample pretreatment involved heating the reaction mixture at 60°C for 45 min and 5 μl portion was analyzed by LC-MS/MS. Results: 3HGA measured in control samples (n=100) ranged between 0-7.1 mmol/mol creatinine. DUS samples from established low-and highexcretor GA1 patients revealed satisfactory results compared to those obtained previously by GC-MS (n=14).