This study tests a device called the I3 Continuous Glucose Monitoring (CGM) system for children with Type 1 Diabetes Mellitus (T1DM). T1DM is a condition where the body doesn’t produce insulin, a hormone that helps control blood sugar. Participants will wear tiny sensors that track their blood sugar levels. Kids aged 2-6 will have two sensors placed on their upper buttocks, while older kids aged 7-17 will have three sensors in different places on their body. Children will continue their regular daily activities and will not see the sensor data to manage their blood sugar. The study involves several clinic visits to check blood sugar levels, with some blood samples taken from older participants (7-17 years old). The study will last 15 days, during which participants will visit the clinic for blood sampling and device check-ups.

• Participants aged 2-6 will have one 4-hour clinic visit.
• Participants aged 7-17 will have three clinic visits, each lasting 6 hours.
• Participants will continue their regular diabetes care and will not change their diet.