The reliability of medical laboratory test results is a key determinant of healthcare quality and patient safety. ISO 15189 is the international reference standard for the accreditation of medical biology laboratories, and its 2022 revision reflects technological advances, organizational changes, and increasing requirements related to performance and risk management. The aim of this study is to conduct a comparative analysis of the major developments introduced in ISO 15189: 2022 compared with the 2012 version, in order to identify conceptual, structural, and operational changes, assess their organizational and technical implications for medical biology laboratories, and highlight the challenges related to patient safety and process performance. This study adopts a qualitative, descriptive, and comparative approach based on a systematic, clause-by-clause analysis of ISO 15189: 2012 and ISO 15189: 2022. This analysis is complemented by a targeted review of the international scientific literature and by an examination of recommendations issued by recognized organizations in the fields of medical biology and quality management. The results reveal major developments, including the reorganization of the standard’s structure in alignment with ISO/IEC 17025: 2017, the explicit and cross-cutting integration of risk management across all laboratory processes, the expansion of the scope to include decentralized medical biology examinations and point-of-care testing, and a stronger focus on patient safety, governance, and the clinical relevance of results. The 2022 version also introduces greater flexibility in demonstrating conformity. In conclusion, ISO 15189: 2022 represents a major conceptual shift, moving from a primarily document-based compliance approach toward a performance-oriented model that emphasizes proactive risk management and patient safety, thereby serving as a strategic lever for continuous improvement in medical biology laboratories.