Inclusion Criteria:

• Type 1 diabetes mellitus diagnosed for at least 12 months prior to signature of informed consent,
• Sub-optimal glycemic control (7.5%<HbA1c<9.5%).
• Patient treated by continuous subcutaneous insulin infusion (CSII) for at least 6 months prior signature of informed consent.
• Patient treated within the practice of the investigator's center at least 6 months prior signature of informed consent.
• Patient has no preliminary experience with the sensor function of the Paradigm REAL-Time or the Guardian® REAL-Time for the 4 months prior signature of informed consent.

Exclusion Criteria:

• Existing pregnancy or intention to conceive (as assessed by investigator).
• Hearing or vision impairment so that glucose display and alarms cannot be recognized.
• Three or more incidents in the last 12 months of severe hypoglycaemia with documented Blood Glucose below 50mg/dL (if possible), resulting in unconsciousness, hospitalisation or third party assistance, where recovery follows treatment with glucose or glucagon or similar.
• History of hypoglycemic unawareness as assessed by the investigator.
• Alcohol or drug abuse, other than nicotine.
• Documented cutaneous allergy or disease (allergy to sensor or components of the sensor, psoriasis, staphylococcus, exanthema etc.).
• Any documented concomitant chronic disease known to affect diabetes control (e.g. altered renal function, active cancer undergoing treatment, Crohn's disease, ulcerative colitis, Mb Addison disease) or any concomitant pharmacological treatment that might modify glycemic values (e.g chronic corticosteroid therapy), eating disorders and morbid obesity (defined as adults : Body Mass Index >35 and children Body Mass Index > 2 standard deviations. for age) as assessed by the investigator.
• Any other medical, social or psychological condition that, in the investigator's opinion, makes the patient unable to comply with the study protocol and all study procedures.
• For pediatric subjects: does not have a reliable support person.
• Plans to travel for extended periods (3+ weeks) where the devices cannot be supplied or replaced and/or medical support is limited (eg. exotic countries, remote places).
• Participation in another clinical study, on-going or completed less than 3 months prior to signature of Patient Informed Consent.