Used as a stable isotope-labeled internal standard in mass spectrometry and liquid chromatography-mass spectrometry (LC-MS/MS) for accurate quantification of progesterone in biological samples such as serum, plasma, and urine. Its isotopic enrichment allows clear differentiation from endogenous progesterone, improving measurement precision in clinical diagnostics, hormone research, and pharmacokinetic studies. Also employed in metabolic studies to trace progesterone pathways without altering biological activity.