Glucose, insulin and glycated hemoglobin levels in oral glucose tolerance test (OGTT) are the basis for the diagnosis of insulin resistance, pre–diabetes, type 1 and type 2 diabetes mellitus. Both in Europe and the United States, the accepted values for the reference range of glucose and insulin in OGTT change every few years. Glucose and insulin levels at 60 and 120 minutes are the most widely used plasma biomarkers, regardless of the new biomarkers and indices, such as hyperinsulinemic–euglycemic clamp, HbA1c, HOMA–IR, etc. In this study, insulin and glucose levels were monitored in 100 clinically healthy controls. The obtained results are discussed on the background of the available new literature data on glucose and insulin.