Patients with systemic lupus erythematosus (SLE) have an increased risk of thrombotic events. Platelets become more active and they enlarge to release proteins from alpha granules for aggregation during the plaque formation period. Beta-thromboglobulin is one of the proteins released from alpha-granules when platelets are activated and used as a marker of platelet activation in vivo.The aim of this study was to evaluate the plasma levels of beta-thromoglobulin and mean platelet volume as markers of the presence of platelet activation in systemic lupus erythematosus patients compared with healthy controls.Thirty-seven SLE patients with a mean disease duration of 4.96 years and without any organ involvement as well as 30 healthy volunteers were included in the study. All patients were in remission of SLE.The mean beta-thromboglobulin level was 97.36 ±55.8 ng/mL in the SLE group and 72.67 ±33.5 ng/mL in the control group (p = 0.029). The mean platelet volume level was 8.27 ±1.68 fL in the SLE group and 9.16 ±1.52 fL (p = 0.031) in the controls.Elevated beta-thromboglobulin levels in systemic lupus erythematosus patients may be associated with platelet activation in the early stages of disease, whereas lower mean platelet volume levels in the same population may be due to the effects of hydroxychloroquine and the inactivity of SLE.