GCK and type 2 diabetes mellitus: In our experience, suspicion of GCK-MODY in contrast to type 1 diabetes at the time of diagnosis increases in the absence of DKA and islet autoantibodies, normal level of fasting C-peptide and presence of diabetes in one parent, whereas in contrast to type 2 diabetes GCK-MODY is suspected in rather normal body mass index/BMI, the absence of insulin resistance (e.g., dyslipidemia, hypertension) or modest rise in 2-h glucose level on oGTT/oral glucose tolerance test (< 4.6 mmol/L in 95% of cases, 12).