Abstract Background Clinical laboratory testing, essential for medical diagnostics, represents a significant part of healthcare activity, influencing around 70% of critical clinical decisions. The automation of laboratory equipment has expanded test menus and increased efficiency to meet the growing demands for clinical testing. However, concerns about misutilization remain prevalent. In Belgium, primary care has seen a dramatic increase in lab test usage, but recent utilization data is lacking. Methods We conducted a comprehensive retrospective analysis of laboratory test utilization trends within the primary care settings of Belgium over a ten-year period, spanning from 2012 to 2021, incorporating a vast dataset of 189 million test records for almost 1.5 million persons. This was the first study to integrate the metadata from both the INTEGO & THIN databases, which are derived from the two major electronic medical record (EMR) systems used in primary care in Belgium, providing a comprehensive national perspective. This research provides crucial insights into patient-level patterns, test-level utilization, and offers international perspectives through comparative analysis. Results We found a subtle annual increase in the average number of laboratory tests per patient (ranging from approximately 0.5-1%), indicative of a deceleration in growth in laboratory test ordering when compared to previous decades. We also witnessed stability and consistency of the most frequently ordered laboratory tests across diverse patient populations and healthcare contexts over the years. Conclusions These findings emphasize the need for continued efforts to optimize test utilization, focusing not only on tackling overutilization but on enhancing the diagnostic relevance of tests ordered. The frequently ordered tests should be prioritized in these initiatives to ensure their continued effectiveness in patient care. By consolidating extensive datasets, employing rigorous statistical analysis, and incorporating international ...