Abstract Background Inappropriate retesting and test request are considered causes of laboratory overutilization. The former can be managed through minimum retesting intervals (MRI) and the latter with expert rules in the laboratory information system (LIS). The aim of this study was to assess the effectiveness of both tools. Methods We performed a retrospective analysis of 14 laboratory routine tests subject to MRI or expert rules among 6 hospitals and 65 primary care centers from March 2018 through December 2023. Both tools were gradually implemented in the LIS (Servolab4®, Siemens, Berlin, Germany). Data from an export software was used for analysis (Health Analytics, Siemens Healthineers, Madrid, Spain). Results During the observation period, a total of 493.640 tests requests were analyzed and 60.151 violations were counted (Table 1). All violations represented an economic saving of 494.603€ (8.760€ per month). The most popular rejected test was 1,25-DihydroxyvitaminD (34,5%), followed by thyroid peroxidase antibodies (20,3%) and 25-HydroxyVitaminD (19%). These three tests were responsible for 73,8% of the total cost savings. Conclusions The real cost estimation of inappropriateness is difficult to assess, but the generated costs for the health system are certainly high and not negligible. Moreover, addressing overutilization would ensure standardization and high-quality care.