Treatment goals in diabetes concentrate on reducing the risk of vascular complications, largely through setting targets for glycated haemoglobin (HbA1c). These targets are based on epidemiological studies of complication development, but so far have not adequately addressed the adverse effects associated with lowering HbA1c towards the normal range. Glucokinase (GCK) mutations cause a monogenic form of hyperglycaemia (GCK-MODY) characterised by fasting hyperglycaemia with low postprandial glucose excursions and a marginally elevated HbA1c. Minimal levels of vascular complications (comparable with nondiabetic individuals) are observed in GCK-MODY, leading to the hypothesis that GCK-MODY may represent a useful paradigm for assessing treatment goals in all forms of diabetes. In this review, we discuss the evidence behind this concept, suggest ways of translating this hypothesis into clinical practice and address some of the caveats of such an approach.