Used as a stable isotope-labeled internal standard in mass spectrometry for accurate quantification of 7-dehydrocholesterol in biological samples. Enables precise measurement in metabolic studies, especially in research related to cholesterol biosynthesis and disorders like Smith-Lemli-Opitz syndrome. Its deuterated structure allows differentiation from endogenous 7-dehydrocholesterol, improving analytical accuracy in LC-MS/MS assays. Also applied in photobiological studies to trace vitamin D3 synthesis pathways under UV exposure, due to its role as a precursor in vitamin D formation.