Process, based on established criteria, of evaluating and controlling the medical necessity for services and providers’ use of medical care resources. Reviews are carried out by allied health personnel at predetermined times during the hospital stay to assess the need for the full facilities of an acute care hospital. In managed care systems such as an HMO, reviews are done to establish medical necessity and appropriateness or efficiency of health care services, thus curbing costs. UR is also monitored by both insurers and employers. Also called medical review, continued stay review, utilization , and management control .