Used as an internal standard in mass spectrometry and liquid chromatography-mass spectrometry (LC-MS) analyses for the accurate quantification of carbamazepine in biological samples such as plasma, serum, and urine. Its deuterated structure provides a distinct mass difference from non-labeled carbamazepine, allowing clear differentiation during detection and minimizing interference from matrix components. This ensures high precision and reliability in therapeutic drug monitoring, forensic toxicology, and pharmacokinetic studies.