Trial to Evaluate the Efficacy and Safety of Gemigliptin Compared With Placebo Added on Insulin Alone or on Insulin in Combination With Metformin in Type 2 DM (ZEUS II Study)

For patients who have been taking metformin, the patients who had taken at least 1000 mg of metformin daily and continue the same dosage and administration as before participant in the study

"doing exercise with about intermediate intensity(50\~70%) for ≥150minutes in total over at least 3 times(every other day) weekly should be recommended and regualr diet without greater changes in life style as much as possible during the whole study period.~the questionnaire regarding diet/exercise will be collected at -week2, week 1 week 7, week 13, week 19, week 25"