BackgroundThere is limited data on platelet alterations in children with type 1 diabetes mellitus (T1DM). We planned to study the effect of glycemic control and duration of T1DM on platelet morphology in children with T1DM. MethodsWe conducted an observational study on 260 children; 130 with T1DM (cases) and 130 healthy controls, in a tertiary care pediatric hospital. Platelet indices including Platelet count (PLT), Mean Platelet Volume (MPV), Platelet Distribution Width (PDW), Platelet-Large cell ratio (P-LCR), Plateletcrit (PCT) were measured, and their means were compared between cases and controls and various subgroups among the cases. ResultsThe MPV, PDW and P-LCR were significantly higher (p < 0.05) in cases when compared to controls and in children with suboptimal glycemic control compared to optimal control. PLT was considerably lower in cases compared to controls. In children with new-onset T1DM, only PDW was significantly raised when compared to controls. MPV and P-LCR had a significant positive correlation with duration of T1DM. ConclusionsChildren with T1DM have altered morphological parameter(s) which progress over time. Poor glycemic control is a significant risk factor for abnormal platelet indices.