This study tests a special device called the **I3 Continuous Glucose Monitoring (CGM) System** for kids with **Type 1 Diabetes Mellitus (T1DM)**. T1DM is when the body can't make insulin, a hormone that helps sugar enter cells for energy, so people need insulin shots. The study checks how well the device works without changing the child's daily routine. Kids aged 2-6 will have sensors placed on their upper buttocks, while 7-17-year-olds will wear sensors at two spots for 15 days. They will visit the clinic for tests where blood sugar, also known as **blood glucose (BG)**, is measured. Kids can eat normally during visits.

• The study lasts 15 days with a few clinic visits.
• Participants will not see their CGM data during the study.
• No changes to regular insulin or food routines except for some older kids.

Children must have had T1DM for at least 6 months and be on a stable insulin plan. Some cannot join, like those with skin issues from adhesives, recent severe low blood sugar, or certain illnesses. If you have questions, talk to the study team for more details.