Observational Study to Evaluate the Effectiveness and Safety Study of the Dexcom G4™ Continuous Glucose Monitoring System

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;