According to the guidelines for GCK-MODY diagnosis, mild fasting hyperglycemia (5.5-8.0 mmol/L), small increase in OGTT (<4.6 mmol/L) at 120 min, negative autoantibodies, and MODY diagnosed in one of the parents are key indications for the genetic screening for GCK mutations. This evidence concerns the gene GCK and MODY.