The purpose of this study is to determine whether a real-time continuous glucose monitoring system is able to improve HbA1c in patients suffering from type 1 diabetes compared to conventional finger prick glucose measurements. In addition it will investigate whether number of episodes with serious hypoglycemia is changed in those same patients, and whether quality of life (health status and treatment satisfaction) increases.

Inclusion Criteria:

1. Diabetes Mellitus, Type 1 > 3 years.
2. For practical reasons patients should live in Trondheim, Malvik, Melhus or Klæbu.
3. Level of HbA1c (measured by DCA 2000) between 7 and 10 % and/or experience blood glucose < 3 mmol/L (verified by finger-prick measurement) at least once a week and/or at least one episode with serious hypoglycemia the previous half a year.(Defined as need of help from others)
4. Only patients who use insulin pumps or multi-injection regime (=3 daily injections with short term acting insulin or insulin analogue + at lest one daily injection with NPH-insulin or long term acting insulin analogue.

Exclusion Criteria:

1. Patients with other diseases such as untreated hypothyroidism, adrenal gland failure, celiac disease, renal failure, unstable coronary heart disease, serious psychiatric disorder, or mental retardation.
2. Patients who are not able to learn how to use the continuous glucose monitoring system given a reasonable amount of effort.
3. Patients who are not able to do the glucose measurements, insulin dose change and diary notes which the study demands.
4. Unsuited for participating from any other cause.