Used as a stable isotope-labeled internal standard in mass spectrometry and nuclear magnetic resonance (NMR) studies to track metabolic pathways and quantify propionic acid and its derivatives in biological samples. Its deuterated form allows for clear differentiation from non-labeled compounds, improving accuracy in analytical measurements. Commonly applied in pharmaceutical research, metabolic profiling, and environmental analysis where precise tracing of organic acids is required. Also employed in synthesis of deuterated compounds for kinetic isotope effect studies.