The purpose of this pilot study is to evaluate performance of the SEVEN System and the Navigator System when both devices are worn concurrently by subjects with type 1 diabetes mellitus.

Inclusion Criteria:

1. Age 18 years or older;
2. Have been diagnosed with type 1 diabetes and are on multiple daily injections (MDI) or Continuous Subcutaneous Insulin Infusion (CSII) insulin therapy;
3. Willing not to inject insulin or wear an insulin pump infusion set within 3 inches from either Sensor site;
4. Willing to participate in an 8-hour in-clinic session on study Days 5, 10, and 15 and be willing to take 4 fingersticks per hour and have 4 blood draws per hour for the 8-hour duration of each of these in-clinic sessions;
5. Willing to take a minimum of 6 fingersticks per day during home use;
6. Willing to refrain from the use of acetaminophen during this study and for at least 24-hours prior to enrollment;
7. Willing not to schedule an magnetic resonance (MRI) scan, computed tomography (CT) scan, x-ray, for the duration of the study;
8. Able to speak, read, and write English.

Exclusion Criteria:

1. Have extensive skin changes/diseases that preclude wearing the Sensor on normal skin (e.g., extensive psoriasis, recent burns or severe sunburn, extensive eczema, extensive scarring, extensive tattoos, dermatitis herpetiformis) at the proposed wear sites;
2. Subjects who have a known allergy to medical-grade adhesives;
3. Are pregnant as demonstrated by a positive pregnancy test within 72 hours of insertion;
4. Have a hematocrit that is less than 30%, or greater than 55%;
5. Current participation in another investigational study protocol (if a subject has recently completed participation in another drug study, the subject must have completed that study at least 30 days prior to being enrolled in this study);
6. Have any condition that, in the opinion of the Investigator, would interfere with their participation in the trial or pose an excessive risk to study staff handling venous blood samples (e.g., known history of hepatitis B or C).

Adults with type 1 diabetes mellitus