Objective With increasing age. The incidence of obesity and diabetes are increasing. As the early or pre-diabetes has no symptoms, the timing of the screening test is very important. Although postprandial hyperglycemia is common in Korean, the fasting plasma glucose and glycosylated hemoglobin are different. It is not known that the usual serum blood glucose and glycated hemoglobin in overweight and obese Korean. Methods Data were from three rounds of nationally representative cross-sectional surveys for Korean men and women adult (7178 in 2008, 7893 in 2009, and 6740 in 2010). A stratified multistage probability sampling design and weighting adjustments were made to obtain a representative Korean population. We calculate the mean value of HbA1c and fasting glucose level according to the age. Results A healthy percentage of the population is 20s 39.0%, 30s 50.3%, 40s 56.9%, 50s 57.4%, 60s 54.2%, and 70s above 37.3%. Glycated hemoglobin(HbA1c) are 20s 6.167%, 30s 7.494%, 40s 7.780%, 50s 7.200%, 60s 6.881%, and 70s above 6.892%. (P < 0.000) Fasting glucose level are 20s 89.683 mg/dL 30s 94.007 mg/dL 40s 98.404 mg/dL 50s 97.784 mg/dL 60s 97.784 mg/dL and 70s above 103.054 mg/dL. (P < 0.000) Fasting serum triglyceride are 20s 129.674 mg/dL, 30s 154.733 mg/dL, 40s 161.562 mg/dL, 50s 161.591 mg/dL, 60s 153.709 mg/dL and 70s above 154.966 mg/dl. (P < 0.000) Conclusion Fasting glucose and TG levels are within normal range, depending on the age. Glycosylated hemoglobin level was increased sharply from the age of 30s. The reason of the mismatch may occur as the postprandial hyperglycemia is common. Further research for the effective diabetes screening test in overweight and obese Korean is needed.