 This is a prospective, non-randomized, open label study to evaluate the performance of the C8 MediSensors non-invasive Optical Glucose MonitorTM on individuals with diabetes mellitus. Capillary blood samples will be obtained throughout a daily study session; the study session may last for up to 12 hours. Blood glucose will be measured on a YSI blood glucose analyzer. Subjects may adjust food intake and insulin administration so device performance is evaluated across a broad range of glucose concentrations. Glucose measurements will be time matched and paired for comparison. Skin effects and adverse events will be evaluated. 