The aim of this study is to assess the results of inspections in the last three years of drug abuse testing in medical laboratories according to the latest regulations in Turkey. The on-site inspections of medical laboratories for drugs abuse testing performed in Alcohol and Drug Addiction Treatment Centers during 2014-2016 are described, and laboratory processes and performance evaluated. The performance of 35 laboratories in 2014, 62 laboratories in 2015, and 94 laboratories in 2016 were scored as the sum of the scores for all answers on the inspection form. An inspected laboratory was considered to have an unconformity if the total score was less than 2/3 of maximum score. The total scores of inspections and the number of laboratories with between years were compared using one-way analysis of variance and slope Chi-square for trend test, respectively. Total scores increased statistically significantly from 35.9 +/- 16.2 in 2014, to 43.5 +/- 16.3 in 2015 and 49.1 +/- 1.3 in 2016 (p < 0.001). The laboratories with unconformities decreased statistically significantly from 57% in 2014 to 37% in 2015 and 22% in 2016 (p < 0.001). The published legislation and the inspections contributed to national standardization and improved quality of service in medical laboratories for drug abuse testing.