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

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;