BackgroundGrade inflation which is known as the awarding of higher grades than students deserve in higher education has been observed since the 1960s. There is comprehensive evidence that document the allegations, prevalence, and severity of grade inflation in higher education in universities around the world for the past 10 years.MethodsThis study analyzes the change in the ratio of graduates with a “very good (>2.99)” degree in medical education in Turkey within a 15-year-long period in terms of the grade inflation (when all other factors are constant), and factors that affect the overall achievement grades. The analyses were carried out using the grade point average (GPA) of 9,618 students who graduated from the medical schools of 25 Turkish universities, and grades of 288,540 students for 7,597 courses. In doing so, the “real” university random effects estimator modelling considering the differences in universities with correlation, ANOVA, t-test and ANCOVA analyses were carried out.ResultsThe results revealed that there was a marginal increase in grades in medical training before graduation. Twenty-nine percent grade inflation was detected in line with the relevant findings in literature and this figure is one of the highest that has been reported so far. It was also detected that the ratio of graduates with a “very good (>2.99)” degree was 17% in 2005 and it increased to 46% in 2020. Additionally, the class size, academic rank of the instructors, grades, course contents, types of the universities (public & non-profit private), accreditation of the program, and the age of the medical schools were considered as important determinants of the difference in course grades.ConclusionThese results show that both the uncontrolled expansion of medical schools in Turkey and the decrease in quality cause a significant increase in grades. Moreover, an important finding is that accreditation slows down the grade inflation. Both the course grades following the accreditation process and the inflation in the graduation grades (grade inflation) slowed down significantly in the accredited medical schools. This finding is an important example for the necessity of accreditation for universities, which is referred to as the “gold standard” to improve the quality of medical education.