Used as a stable isotope-labeled internal standard in mass spectrometry and chromatography for accurate quantification of docosahexaenoic acid (DHA) in biological samples such as plasma, serum, and tissues. Its deuterated structure allows differentiation from endogenous DHA during analysis, improving measurement precision in metabolic studies, nutritional assessments, and clinical diagnostics. Commonly applied in research on omega-3 fatty acid metabolism, brain development, and inflammatory processes.