This is an open-label, mono-centre, interventional study.The aim of this trial is to assess accuracy and reliability of a flash glucose monitoring system, the freestyle Libre (Abbott, CA, USA), in patients with type 1 diabetes.

Objective: To assess accuracy and reliability of a new-to-market flash glucose monitoring system, the freestyle Libre (Abbott, CA, USA), in patients with type 1 diabetes.

Study design: open-label, mono-centre interventional study. Patients will wear freestyle Libre for 14 days in the home setting. There will be no limitations in food intake or in physical activity, but patients will have at least 7 finger-stick/days. Patients will have 2 visits in our clinical center and in these visits we'll compare freestyle Libre values with blood sampling to determine glucose values with YSI, during euglycemia and during glucose excursion and induced hypo-hyperglycemia.

Study population: 48 patients will be included in this trial. Every patient will wear device for 14 days at home and during 2 visits at CRC Study endpoints: main endpoint will be the evaluation of freestyle Libre accuracy during real life compared to glucometer values and to YSI glucose values (during 2 visits). A separate analysis will be performed on the accuracy of the freestyle Libre in the hypoglycaemic (defined as a blood glucose value ≤3.9 mmol/L) and hyperglycaemic area (defined as a blood glucose value ≥10.0 mmol/L). Additionally, a separate analysis will be performed to assess device performance and accuracy per day of device life.

If patients enrolled in the study use Dexcom G4 or G5 (CGM) and wanted to continue to use it, he/she can do so. In this case we can compare the accuracy of Libre even towards Dexcom G4/G5 device.

Inclusion Criteria:

• Age > 18 years
• Diagnosis of diabetes mellitus type 1 ( diagnosed according to World Health Organization criteria ) for at least one year
• Body Mass Index ( BMI ) < 35 kg / m²
• Willingness to wear the device and to comply with the study protocol during the entire duration of the same
• No restrictions linked to glycated hemoglobin ( HbA1c )
• Signature of informed consent before any study-related procedure

Exclusion Criteria:

• Pregnancy, breast-feeding, planning pregnancy, or refuse to use contraception during the study period (for female subjects).
• Known allergies to patches or skin disinfectants used during the study.
• skin lesions, irritation, redness, edema, in the possible application of the sensor sites that may interfere with the placement of the device or the detection accuracy of test results.
• blood donations in the 3 months preceding the study.
• Use of drugs that can interfere with glucose metabolism (such as steroids) unless it is chronic therapies whose dosage has remained stable over the last 3 months and is expected to remain stable during the study period.
• serious medical or psychological conditions that in the opinion of the medical team could compromise patient safety during study participation.
• Patients enrolled in other clinical trials.
• known disorders of the adrenal glands, pancreatic tumors, or insulinomas
• Inability of the patient to comply with the study procedures