At week 24 , the meanstandard error ( s.e. ) HbA1c decreased from baseline by -2.80.1 % with linagliptin/metformin and -2.00.1 % with linagliptin ; a treatment difference of -0.8 % ( 95 % confidence interval -1.1 to -0.5 ; p < 0.0001 ) .