Subjects with stable type 1 diabetes mellitus on multiple daily insulin injections including basal and bolus will be selected in order to determine the correct insulin dosing formulas. Subjects will be placed on continuous glucose sensor (CGMS) and an isocaloric diet. Subjects will have the CGMS downloaded daily and the insulin doses adjusted if necessary. Subject will do four SMBGs daily to calibrate CGMS and on last day a 7-point SMBG. subjects will be on lispro and glargine insulin. Basal insulin will be once a day.