Diabetes represents a conglomerate of diseases with chronic hyperglycaemia as hallmark. The present review discusses those diabetic cases that associate with variants in genes that affect the magnitude of the glycolytic flux and oxidative disposal of glucose by mitochondria in pancreatic beta-cells. These genetic variants result in an attenuated secretion of insulin in response to glucose stimulation. The diabetic states that associate with these genetic variants are MODY 2, thiamine responsive anaemia syndrome (TRAS) and mitochondrial diabetes. These disease states highlight the critical contribution of the carbohydrate flux through glycolysis and mitochondria and its coupling to ATP production in determining insulin secretion.