GCK and diabetes mellitus: Only two mutations have been reported that cause exceptionally high postprandial glucose levels.26 Additionally, HbA1c levels are lower in GCK‐MODY than other types of MODY and diabetes.4 In a recent study, HbA1c reference range in GCK‐MODY children was 5·6–7·3% (37·7–56·3 mmol/mol) and provided good sensitivity and specificity for discriminating hyperglycaemia likely to be caused by a GCK mutation.6 Although the HbA1c levels in this study were within expected range except one, the glucose increments in OGTT were slightly higher than expected.