Visit three (4-14 days after visit 2, research facility) This will be as visit 2 with participants given the alternative treatment (DPPIV inhibitor or no treatment). Participants will be asked to keep glucose-lowering therapy identical between visits 2 and 3, to attend the research department at a similar time of day as visit 2 and to take evening insulin prior to visit 3 at the same time and dose as prior to visit 2.