Used as a stable isotope-labeled internal standard in mass spectrometry-based assays for accurate quantification of nicotinamide in biological samples. Enables precise tracking of metabolic pathways involving NAD+ and its precursors in research on cellular metabolism, aging, and mitochondrial function. Commonly applied in pharmacokinetic and metabolic studies to distinguish exogenous from endogenous nicotinamide. Also utilized in studies investigating vitamin B3 metabolism and deficiency disorders.