Phenmetrazine, a Schedule II stimulant once prescribed as an appetite suppressant, is a target analyte in urine drug testing and postmortem toxicology, where accurate identification is critical for clinical interpretation and cause-of-death determinations. Its structural similarity to amphetamines and other phenethylamines demands rigorous differentiation in forensic drug seizure analysis and workplace drug monitoring programs. This CRM supports accurate quantification and confirmatory testing via LC-MS/MS and GC-MS, addressing the challenges of isobaric interference and low-abundance detection in complex biological matrices.