The purpose of the study is to test the accuracy benefit of having two glucose sensors (over one sensor alone) when they are positioned: 2mm, 10mm, 20mm, or 30mm apart. It is not yet known how close two sensors can be and still work correctly.

An artificial pancreas system will likely require multiple glucose sensing elements to function safely. It is not yet known how close two glucose sensors can be placed and still work properly. Meaning, if one is reading inaccurately,and the other is positioned adjacent to it, will it read inaccurately also, defeating the purpose of having two sensors. Twenty adult subjects with Type 1 diabetes will wear four Medtronic REAL-Time glucose sensors during two separate 10-hour studies. The inter-sensor distances of each pair to be tested will be: 2, 10, 20, and 30mm apart. The sensors will be inserted the day prior to the study day to allow for signal stabilization and calibration. During the study day, arterialized venous blood will be drawn every 15 minutes to measure blood glucose. The sensor values and interstitial values will be recorded from each sensor receiver at each time point. Subjects will be fed two standardized meals and given pre-meal insulin based on their typical insulin to carbohydrate ratio.

Inclusion Criteria:

1. Type 1 diabetes mellitus diagnosed for at least 6 months
2. Current usage of multiple daily injections or subcutaneous insulin pump treatment
3. Age 18-65 years
4. HbA1c of 6.0 - 9.5% at screening visit
5. BMI 21-35
6. Willingness to follow all study procedures, including attending all clinic visits
7. Willingness to sign informed consent and HIPAA documents

Exclusion Criteria: Subjects presenting with any of the following will not be included in the study.

1. Pregnancy or Lactation: for women of childbearing potential there is a requirement for a negative urine pregnancy test.
2. Renal insufficiency (serum creatinine of 2.0 mg/dL or greater). Serum ALT or AST equal to or greater than 3 times the upper limit of normal; hepatic synthetic insufficiency as defined as a serum albumin of less the 3.3 g/dL; or serum bilirubin of over 2.
3. Hematocrit of less than or equal to 34%.
4. Congestive heart failure, NYHA class III or IV.
5. Visual impairment preventing reading of glucose meter values.
6. Active coronary artery disease as manifested by unstable angina, or a myocardial infarction or therapeutic coronary percutaneous procedure (e.g., PTCA, stent placement) or CABG within the past 4 months.
7. Active foot ulceration.
8. Severe peripheral arterial disease characterized by ischemic rest pain or severe claudication.
9. Cerebrovascular accident within the past 6 months.
10. Active alcohol abuse, substance abuse, or severe mental illness (as judged by the principal investigator).
11. Active malignancy, except basal cell or squamous cell skin cancers.
12. Major surgical operation within 30 days prior to screening.
13. Seizure disorder (epilepsy).
14. Any concurrent illness, other than diabetes, that is not controlled by a stable therapeutic regimen.
15. Currently administration of oral or parenteral corticosteroids.
16. Use of an investigational drug within 30 days prior to screening.
17. Bleeding disorder, treatment with warfarin, or platelet count below 50,000.

clinical practice Type 1 patients