Osteocalcin, a bone-derived protein, has recently been reported to affect energy metabolism, this study aimed to evaluate the effects of osteocalcin level on blood glucose concentration and insulin level in type II diabetic Sudanese patients. In this cross-sectional study, one hundred fifteen type II diabetic patients were enrolled in the study (34 males and 81 females) with ages ranging between 18 and 90 years. Total osteocalcin, undercarboxylated osteocalcin, and insulin were measured using ELISA technique. Fasting blood glucose and lipid profile were measured by a spectrophotometer. Mean serum osteocalcin concentration in diabetic patients was significantly lower than those in control subjects (p ≤ 0.001). Undercarboxylated osteocalcin in diabetic patients was significantly lower than in control subjects (p ≤ 0.001). Fasting insulin was significantly higher in diabetic subjects compared to control subjects (p ≤ 0.001). Osteocalcin was negatively correlated with insulin and FBS (r = −0.530; p ≤ 0.001), (r = −0.373; p ≤ 0.001) respectively. Undercarboxylated was negatively correlated with insulin and FBS (r = −0.634; p ≤ 0.001), (r = −0.297; p ≤ 0.001) respectively. Total osteocalcin and undercarboxylated osteocalcin levels of diabetic patients were lower than those of the healthy control subjects. Fasting serum insulin was higher in patients compared to control subjects. Total osteocalcin and undercarboxylated osteocalcin were negatively correlated with Fasting serum insulin and FBS.