Used as an internal standard in mass spectrometry for accurate quantification of tenofovir in biological samples such as plasma, serum, and urine. Enables reliable measurement in pharmacokinetic studies, therapeutic drug monitoring, and bioavailability assessments. Its deuterated structure allows clear differentiation from non-labeled tenofovir, minimizing interference and improving analytical precision in LC-MS/MS workflows. Commonly applied in clinical and pharmaceutical research involving antiretroviral therapy for HIV and hepatitis B.