The purpose of this clinical investigation is to evaluate the accuracy of the Senseonics Continuous Glucose Monitoring System (Senseonics CGM System) measurements when compared with reference standard measurements (YSI glucose analyzer). The investigation will also evaluate safety of the Senseonics CGM System usage, while in the clinic and during home use.

Inclusion Criteria:

Subjects meeting all of the following inclusion criteria will be included in this study:

1. Males and females ≥18 years of age
2. Clinically confirmed diagnosis of diabetes mellitus for a duration of 1 year and uses insulin therapy for their diabetes management (including subjects on insulin pump therapy)
3. Subject has signed an informed consent document and is willing to comply with protocol requirements

Exclusion Criteria:

Subjects meeting any of the following exclusion criteria will be excluded from this study:

1. History of severe hypoglycemia in the last 6 months prior to study start, defined as hypoglycemia resulting in loss of consciousness or seizure
2. Diabetic ketoacidosis in the past 6 months
3. Any condition preventing or complicating the placement, operation or removal of the Sensor including upper extremity deformities or skin condition.
4. Any medical condition or illness that in the judgment of the investigator might interfere with the procedures, results or compliance during the course of this investigation, or increase the risk of induced hypoglycemia or repeated blood testing including significantly impaired hepatic function and renal failure
5. Known microvascular (diabetic) complications, including active proliferative diabetic retinopathy or macular edema, active non-proliferative retinopathy, diabetic nephropathy including active retinopathy
6. Hematocrit >50% or <30%
7. Females lactating or pregnant or intending to become pregnant during the course of the investigation
8. A condition requiring or likely to require magnetic resonance imaging