Twenty (20) children with T1DM will be recruited for these studies. These children will be subjects of the Texas Children's Hospital Diabetes Care Center. The subjects must be:

1. Between 12-21 years of age at the time of enrollment.

2. Have been diagnosed with diabetes for at least 2 years and in good control (HbA1C less than 8.5%).

3. Be on continuous subcutaneous insulin infusion using an insulin pump.

4. Subjects must be otherwise healthy except for their T1DM and treated hypothyroidism.

5. Menstruating women must have a negative pregnancy test.

6. Hemoglobin equal to or > 12 g/dL before each study.

7. Weight more than 44 kg. -

1. Age greater than 22 years or less than 12 years at the time of study

2. Any chronic disease: leukemia, asthma, inflammatory bowel disease, cystic fibrosis, juvenile rheumatoid arthritis, etc or on treatment that might directly or indirectly affect glucose homeostasis, except for diabetes and hypothyroidism stable on medications

3. Anemia (hemoglobin less than 12mg/dl)

4. Lack of a supportive family environment

5. Positive pregnancy test in menstruating young women

6. Evidence or history of chemical abuse

7. Hgb A1C greater than or equal to 8.5 % in a diabetic subject

8. BMI > 90 % tile for age or < 10 % tile for age

9. Weight less than 44 kg. -