In previous study the investigators proved that blood glucose after eating pizza margherita could be managed with a simple wave bolus of insulin in pediatric patients with type 1 diabetes under controlled conditions. Participants in this previous study were Predictive Low Glucose Suspended (PLGS) System users. In this study the investigators want to demonstrate that blood glucose after the meal pizza margherita could also be managed with simple wave bolus of insulin in real life. The investigators will include just the patients with Hybrid Closed Loop (HCL) System.

The investigators will enroll all patients with type 1 diabetes using of Hybrid Closed Loop (HCL) Systems (Medtronic MiniMed 780 G insulin pump system, Tandem T: Slim X2 insulin pump) followed in a diabetes center. The patients aged between 8- 18 will be included in the study just in a condition of using HCL Systems at least 3 months. Patients with HbA1c >8.5 % (69 mmol/mol), celiac disease, other food allergies will be excluded. The investigators will ask to parents feeding children with a pizza margherita which contains 100 grams of carbohydrates. Even if the patients could choose to consume pizza in different restaurants, the investigators will suggest having the pizza prepared with 200 grams of dough (which contains about 100 grams of carbohydrate). To validate the results the investigators will compare, for each patient, the data of glucose sensor and insulin pump after pizza consumption with those resulting from the consumption of a meal with the same macronutrient content. Patients should not consume anything else for 12 hours after the pizza (and after the meal containing the same macronutrient content). For this reason, patients will be encouraged to have these meals for dinner.

The aim of the study is comparing pizza with another meal which contains similar macronutrients. Second goal of this study is evaluating the blood glucose profile after eating pizza comparing the competency of two different Hybrid Closed Loop (HCL) Systems (Medtronic MiniMed 780 G insulin pump system, Tandem T: Slim X2 insulin pump) to manage blood glucose after eating pizza.

The investigators will collect data from both Carelink (for Medtronic device) and from Diasend (from Tandem device). All data will be exported in an excel file.

Demographic and clinical characteristic of enrolled patients (sex, BMI, Zscore BMI), HbA1c) will be collected from their medical records.

Observation period: from the dinner bolus to the next 10 hours of fasting.

Data from glucose sensor:

Endpoints from the sensor data will be evaluated:

• Percentage of time in targets with sensor glucose (SG) cut-offs of <54 mg/dl, ≤54>70mg/dl, ≥70<140mg/dl, ≥70 <180; ≥180<250 mg/dl and ≥250 mg/dl
• Coefficient of variation (%)
• Average Sensor Glucose SD (mg/dl) Times in target will be evaluated over the entire observation period (10 hours after bolus), from the bolus administration to 2 hours after administration, and from 2 to 5 hours after administration.

Data about insulin dose:

Endpoints from insulin pump will be evaluated:

• Total insulin dose (IU): it will be calculated as the sum of total basal insulin (IU) and total bolus insulin (IU) infused during the entire observation period.
• Total bolus amount (IU and %)
• Autocorrection bolus amount (IU and %)
• Autobasal amount (IU and %)

Data about carbohydrates amount:

Total carbohydrates amount entered during the observation period

Data about automatic mode:

Percentage of time in AutoMode during the observation period

The investigators will compare data of:

• "Pizza consumption" vs "control meal";
• "Medtronic pizza management" vs "Tandem T slim pizza management"

Inclusion Criteria:

• The patients aged between 8- 18 will be included in the study just in a condition of using HCL Systems at least 3 months

Exclusion Criteria:

• Patients with HbA1c >8.5 % (69 mmol/mol), celiac disease, other food allergies will be excluded.

We will enroll all patients with type 1 diabetes using of Hybrid Closed Loop (HCL) Systems (Medtronic MiniMed 780 G insulin pump system, Tandem T: Slim X2 insulin pump) followed in our diabetes center.