The purpose of this study is to evaluate the effectiveness and safety of the Dexcom G4 System when used as an adjuvant to blood glucose testing.

Device performance will be primarily evaluated in terms of the proportion of glucose values within a pre-specified range compared to reference values.

Safety data of the G4 System will also be collected vis-a-vis adverse event reporting characterized by the incidence and severity of Serious Adverse Device Events, and Adverse Device Events experienced by study participants.

Inclusion Criteria:

1. Age 18 years or older;
2. Have been diagnosed with insulin-requiring diabetes
3. Abstain from injecting insulin or wear an insulin pump insertion set within 3 inches from the sensor site during sensor wear;
4. Insert sensors on their own and wear 2 systems simultaneously;
5. Use only the blood glucose meter provided for all blood glucose measurements performed during sensor wear and not allow others to use this meter during the study;
6. Participate in one in-clinic session comprising of fingersticks per hour and have blood draws for the entire in-clinic session;
7. Have an intravenous catheter inserted for 4 blood draws per hour
8. Willing to perform SMBG during home use with the meter provided;
9. Refrain from the use of acetaminophen during sensor wear period and the day prior to sensor insertion;
10. Speak, read, and write English;
11. Willing and able to be compliant with provisions laid out in this protocol.

Exclusion Criteria:

1. Have extensive skin changes/diseases that preclude wearing devices 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. Allergy to medical-grade adhesives;
3. Pregnant as demonstrated by a positive pregnancy test within 72 hours of sensor insertion,
4. Dialysis treatment;
5. Hematocrit that is outside the range of 30-55% at screening visit;

Subjects that fit the inclusion criteria will be chosen from the general population