All subjects will participate in one, 8-hour in-clinic session on Day 1, 4, or 7 of the study to collect accuracy information against a laboratory standard (YSI) and against SMBG. During the in-clinic session, subjects will have venous blood draws for evaluation of the YSI blood glucose measurements. Carbohydrate consumption and insulin dosing may be manipulated during the in-clinic session to ensure a wide range of glucose values. For the duration of this study, subjects will be instructed to use G4 System information as an adjunct to (and not as a replacement for) standard SMBG guidance of diabetes self-management.