Used as a stable isotope-labeled internal standard in mass spectrometry-based assays for the quantification of cholestanol and related oxysterols in biological samples. Its deuterated structure allows for accurate differentiation from endogenous compounds during analysis, improving precision in metabolic studies. Commonly applied in research on cholesterol metabolism, particularly in investigations of neurodegenerative diseases and inborn errors of metabolism such as cerebrotendinous xanthomatosis. The 5α,6α-epoxy configuration enhances its utility in studying oxidative cholesterol pathways.