Ninety percent of patients with type-1-diabetes will develop late-diabetic complications in the eyes, kidneys, nervous- or cardiovascular-system. Poor glycaemic control is an important risk-factor for development of these late-diabetic complications. The Diabetes Control and Complications Trial (DCCT)-study showed, that improved glycaemic control can prevent the development and progression of these late-diabetic complications. Until now treatment with insulin- and diet-therapy has been the only treatment-modalities available to improve the glycaemic control in patients with type-1-diabetes. A substantial number of these patients still have long-standing poor glycaemic control despite intensive treatment with insulin- and diet-therapy.

The antidiabetic drug metformin has shown to be able to improve the glycaemic control in combination with insulin and furthermore reduce both mortality and the risk of developing cardiovascular disease in patients with type-2-diabetes.

Only few small studies have investigated the effect of treatment with metformin in patients with type-1-diabetes. These studies have suggested a positive effect of metformin in these patients too.

Method:

100 patients with type-1-diabetes with persistent poor glycaemic control i.e. HbA1c > 8.5% during the last 12 months are eligible. Patients are treated for one month with placebo. Hereafter half of the patients will be treated with metformin and the other half continues with placebo for 12 months both as add-on therapy. All patients are continuing ongoing treatment with insulin throughout the study. Before and after the start of treatment with metformin the effect on glycaemic control and other known risk-factors for development of cardiovascular disease i. e. blood-pressure, fasting lipids, urine-albumine-excretion, endothelial dysfunction, inflammation, fibrinolysis etc. is assessed.

This study will show if treatment with metformin can improve the glycaemic control and hereby the prognosis of patients with type-1-diabetes with persistent poor glycaemic control despite intensive treatment with insulin- and diet-therapy. This group of patients suffers the highest risk of developing late-diabetic complications with reduced quality of life and life-expectancy as a consequence.

Inclusion Criteria:

• HbA1c > 8.5% for more than one year prior to enrolment.
• Diabetes-duration > 5 years.
• Age at onset of diabetes < 35 years
• Fasting C-peptide < 300 pmol/l
• Age > 18 years at enrolment.

Exclusion Criteria:

• Clinical or biochemical signs of kidney-, liver- or heart-failure.
• Other coexisting serious morbidity, which will affect the study-participation or outcome of the study i.e. cancer.
• Known abuse of any medication or alcohol
• Hypoglycaemia unawareness.
• Pregnancy or planned pregnancy in the study-period.