Recently, there have been many studies on the relationship between the bone metabolism and the mechanism of diabetes. In those studies, it was shown that osteocalcin can be involved in the treatment of type 2 diabetes. Therefore, this study examined the correlation between osteocalcin and HbA1c. From January 1, 2015 to December 31, 2016, a total of 714 adults aged 40 years or older (70.8±10.4 years, 452 males), in whom both osteocalcin and HbA1c checked in a general hospital in Gwangju, were enrolled in the study. The serum calcium, total cholesterol, triglyceride, HDL-cholesterol, LDL-cholesterol, and 25-(OH) vitamin D were measured and basic information, such as the height and weight, were recorded. There was a weak negative correlation (r=？0.183, P＜0.001) between the osteocalcin and HbA1c levels in diabetic patients but a negative correlation (r=？0.251, P＜0.001) when adjusted by all other study variables. The present study showed that there was a negative correlation between the osteocalcin and HbA1c levels in diabetic patients. The relationship between the bone metabolism and the incidence of diabetes mellitus should be studied based on the influence of biological mechanisms and associated factors of bone and glucose metabolism.