The investigators hypothesize that the use of an oral dose of Terbutaline or a 20% basal reduction will be able to prevent nocturnal hypoglycemia after an afternoon exercise session. This is a randomized three period cross-over study including treatment with Terbutaline, a 20% basal reduction for six hours, or no treatment (control).

In this study, a minimum of 16 youth with type 1 diabetes will be recruited. All subjects must have been diagnosed with type 1 diabetes for at least one year and on an insulin pump for at least one month. Subjects are between the ages of 10 and 17 years, inclusive, have an HbA1c less than 10.0% and normal thyroid function. Subjects can not have had a severe hypoglycemic episode in the last three months, any other illness or treatment that may affect the wearing of a continuous glucose monitor or the completion of the study as determined by the investigator. Subjects may not use drugs containing pseudoephedrine within 48 hours of the study visits.

This study consists of three overnight visits at the Clinical Translational Research Center. Meals eaten during the study will be consistent for each of the three visits.

Subjects will participate in a standardized afternoon exercise session on a treadmill as has been done in previous Diabetes Research in Children Network studies. Exercise will begin at 4pm and must be completed by 6pm. Dinner will be eaten at the end of the exercise.

At 9pm, treatment will be given as determined by the randomization group the subject is assigned to. The treatment includes either an oral dose of 2.5mg Terbutaline, a 20% basal reduction for six hours or no treatment as the control. Blood glucose levels will be measured every 30 minutes until 6am.

Inclusion Criteria:

• Clinical diagnosis of Type 1 Diabetes and using daily insulin therapy for at least one year.
• Age 10 to 17 years, inclusive.
• HbA1c < 10.0%.
• BMI 5-95th % for age and gender.
• Stable Continuous Subcutaneous Insulin Infusion regimen for at least 1 month and not anticipating a change prior to the subject's completion of the study.
• Subject uses a downloadable insulin pump.
• Normal thyroid function (measured within the previous year).
• For females, subject not intending to become pregnant during the study.
• No expectation that subject will be moving out of the area for the duration of the study.
• Informed consent form signed and understood by the parent/guardian and Child Assent form signed/understood by subjects.

Exclusion Criteria:

• The presence of a significant medical disorder (including epilepsy, or any cause of seizures other than hypoglycemia) that in the judgment of the investigator will affect the wearing of the sensors or the completion of any aspect of the protocol.
• A recent injury to body or limb, Addison's disease, muscular disorder or disease in the judgment of the investigator that will affect the completion of the exercise protocol.
• Asthma which has been medically treated within the last year.
• Medically diagnosed cardiac disease, hypertension, or autonomic dysfunction.
• Use of pseudoephedrine 48 hours prior to the visit (if used in the 48 hours prior to the scheduled visit, the visit will be deferred)
• Severe hypoglycemia resulting in seizure of loss of consciousness in the 3 months prior to a visit.
• Active infection (if at the time of the scheduled visit and infection is present, the visit will be deferred).
• Anticipating a significant change in exercise regimen between visits (i.e. starting or stopping an organized sport).
• Treatment with systemic or inhaled corticosteroids in the last 6 months.
• Current treatment with B-blockers or presenting with high blood pressure.
• Inpatient psychiatric treatment in the past 6 months for either the subject or the subject's primary care giver.
• Current use of oral/inhaled glucocorticoids or other medications, which in the judgment of the investigator would be a contraindication to participation in the study
• Known allergy to Terbutaline
• Treatment with atenolol (Tenormin), carteolol (Cartrol), labetalol (Normodyne, Trandate), metoprolol (Lopressor), nadolol (Corgard), phenelzine (Nardil), propranolol (Inderal), sotalol (Betapace), theophylline (Theo-Dur), timolol (Blocadren), tranylcypromine (Parnate), other medications for asthma, heart disease or depression.
• Treatment with ephedrine, phenylephrine, phenylpropanolamine, or pseudoephedrine.
• The presence of an irregular heart beat, increased heart rate glaucoma or an overactive thyroid gland.