This study will be conducted in subjects with Type 1 diabetes mellitus on multiple daily insulin injections to determine the correct insulin dosing formulas. Subjects will be evaluated using continuous glucose monitoring.

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.

Inclusion Criteria:

• Age: >17 years
• Type 1 diabetes
• Diabetes duration > 3 months
• On treatment with multiple daily injections either one or more basal insulin injections each day for 6 weeks
• HbA1c <9.0%
• Stable HbA1c in the proceeding 3 months (i.e., change <1%)
• Demonstrated adherence to visits and instructions
• Attend a class in meal carbohydrate content estimation or have demonstrated knowledge of carbohydrate counting

Exclusion Criteria:

• Major stress event during or for 6 weeks before the evaluation
• Taking a medication that can alter insulin sensitivity
• Within one week of menses
• Unstable eating or activity pattern
• Pregnancy
• Weight gain of > 1.5 kg during the preceding 3 months
• Serum creatinine of >1.5 mg/dl
• Active liver disease
• Evidence of autonomic neuropathy, especially gastroparesis
• Any antidiabetic medication other than insulin
• Treatment with continuous subcutaneous insulin infusion