The use of deuterium in the pharmaceutical industry has expanded in recent years as medicinal chemists seek to design compounds with improved and favorable metabolic profiles, hoping to increase the success rate of compounds in the clinic. As a result, process and analytical chemists face new challenges in terms of tracking isotopologues and isotopomers to ensure the quality of intermediates and active pharmaceutical ingredients through manufacture. The work presented herein describes the discovery of an overdeuterated isotopologue, which spurred the development of a simple mitigation strategy. The risk associated with utilizing the overdeuterated isotopologue is examined by kinetic studies of a downstream C–H functionalization reaction.