['To examine the association between mean platelet volume (MPV) and glycated hemoglobin (HbA1c) in a large cohort of unselected outpatients.', 'We retrospectively reviewed combined results of complete blood count (CBC) and hemoglobin A1c (HbA1c) performed in all outpatients aged 18 years or older, who were referred to the outpatient clinic of our hospital for routine health check-up during the year 2013.', 'Cumulative results of both CBC and HbA1c could be retrieved for 4072 male and female outpatients aged 18 years or older. There were significant associations between HbA1c and both MPV (r=0.10; p<0.001) and platelet count (r=0.05; p<0.001), that remained statistically significant after adjusting for age and sex. After stratifying the whole sample of patients for MPV quartiles, there was a significant, positive trend of HbA1c across quartiles of MPV (p<0.001). Similar findings were found when the whole sample was stratified by clinical thresholds of HbA1c (p<0.001), with values of MPV gradually increasing from subjects with normal glucose homeostasis, pre-diabetes and diabetes.'] Is the mean platelet volume significantly associated with higher glycated hemoglobin in a large population of unselected outpatients?