Abstract Background It has been previously shown that platelets of patients with diabetes are more reactive and less responsive to anti-platelet drugs compared with platelets from subjects without diabetes. Studies examining the effect of glycemic control on platelet reactivity have yielded conflicting data. Thus, in this study, we sought to explore the effect of tight glycemic control on platelet reactivity in patients with long standing uncontrolled diabetes. Methods The study included 30 patients with long-standing treated diabetes and a baseline HbA1c level of≥8.5%. All patients were treated with aspirin and statins. Patients were tested at baseline and after 3months of intensive glycemic and metabolic control. The treatment goal was to achieve a HbA1c level of ≤7%. Platelet reactivity was assessed by light transmission aggregation in response to 5 and 10μM ADP and to 0.5mg/ml arachidonic acid (AA). Additonally, platelet activation was assessed by plasma levels of soluble P-selectin using an enzyme-linked immunosorbent assay. Results The mean duration of diabetes from the time of diagnosis was 20.46±9.31years. Baseline HbA1c was 9.4±0.8%. Following the intensive glycemic control period, the HbA1C level decreased to 8.1±0.8% (P<0.0001). Other laboratory parameters did not change significantly except for triglyceride levels, which decreased. None of the platelet aggregation studies nor P-selectin levels differed between baseline and after 3months of intensive glycemic control. Conclusions Intensive glycemic control in patients with longstanding uncontrolled diabetes does not seem to result in a reduction in platelet reactivity.