The purpose of the investigation is to obtain sufficient preliminary information about the performance of the TrueVie Continuous Glucose Monitoring (CGM) device to identify any need for any design modifications.

After being informed about the study and potential risks, all participants giving written informed consent will be screened for participation. Qualifying participants will insert CGM sensors and come to 3 clinic visits at the beginning, middle and end of the 15 days intended sensor life. At the clinic visits participants are served two meals and perform a brief period of exercise of moderate intensity while blood samples are drawn according to a planned schedule timed to coincide with the TrueVie measurements.

Inclusion Criteria:

1 Type 1 diabetes mellitus 2. Must be and have been in stable treatment regimen for at least 3 months with a multiple daily insulin dosing regimens or Continuous Subcutaneous Insulin Infusion (CSII), irrespective of delivery device(s).

3. Must have normal exercise tolerance.

Exclusion Criteria:

1. Skin adhesive tolerance issues in the area of sensor placement
2. HbA1c > 9%.
3. Insulin meal dosing based on fixed dose regimens.
4. Absence of established corrective factor for high glucose.
5. Hematocrit below 10% under the lower limit of the normal range.
6. Body mass index < 20 kg/m2.
7. Inadequate intravenous access on arms.
8. Absence of moderate exercise tolerance per history
9. Pregnancy, planned pregnancy within the study period, or unwillingness to use reliable contraception during the study period.
10. Planned MRI, CT scan or diathermic procedure for the duration of the study.
11. Any medical history of malignant melanoma or breast cancer.
12. Medical history of any other cancers within the last five years except adequately treated basal cell or squamous carcinoma of the skin, or cervical carcinoma in-situ.
13. History of alcohol or drug abuse within the last year.
14. Any condition that in the opinion of the investigator may interfere successful completion of study procedures.
15. Participation in other clinical trials involving receipt of investigational drug that cannot be disclosed within the last 30 days.
16. Inability or unwillingness to conform to the required protocol procedures including giving informed consent.

Patients with type 1 diabetes