It is known that there is considerable variation in treatment response to glucose lowering therapy in type 2 diabetes but, to date, there has been no description of any subgroups that respond with a dramatic 5 percentage point (31 mmol/mol) change in HbA1c, as observed in individuals with HNF1A-MODY. The gene discussed is HNF1A; the disease is type 2 diabetes mellitus.