Clinical and Laboratory Standards Institute guideline C52—Toxicology and Drug Testing in the Medical Laboratory helps medical laboratories develop procedures for analyzing drugs of abuse and other compounds. C52 provides guidance on clinical toxicology testing from the initial consultation through final result reporting and interpretation, and includes a variety of specimen types, analytical procedures, and instrumentation. This guideline discusses the most common purposes for clinical toxicology testing, including the support of emergency medicine, obstetrics and gynecology, neonatology, pediatrics, psychiatry, pain management, and addiction medicine. The primary objective is to ensure high-quality standards are maintained throughout the entire testing process, from specimen collection, processing, and analysis, through results reporting and interpretation.