Used as a stable isotope-labeled internal standard in mass spectrometry-based assays for accurate quantification of oxysterols and related steroidal metabolites in biological samples. Its deuterated structure allows for reliable differentiation from endogenous compounds, improving precision in metabolic studies, clinical diagnostics, and pharmacokinetic research involving cholesterol oxidation products. Commonly applied in studies of neurodegenerative diseases, lipid metabolism disorders, and oxidative stress due to the role of oxysterols as biomarkers.