The purpose of the study is to evaluate if supplementation with vitamin D in a dose of 40.000 IU per week will result in improved metabolic control in patients with type 2 diabetes.

The purpose of the study is to evaluate if supplementation with vitamin D in a dose of 40.000 IU per week will result in improved metabolic control in patients with type 2 diabetes.

We will include 70 patients with type 2 diabetes. They will be treated with 40.000 IU cholecalciferol per week (or placebo) for 6 months. Metabolic control will be evaluated with measurements of glycated hemoglobin, home glucose measurements, and fasting blod glucose and serum insulin. Only subjects using insulin at bedtime combined with metformin during the day will be included.

Inclusion Criteria:

• Type 2 diabetes for at least 1 year
• age 21-75 years
• long-acting insulin at bedtime
• metformin during the day
• for women of child bearing age use of reliable method of birth control

Exclusion Criteria:

• serum creatinine above 130 umol/l for men and above 110 for women
• systolic blood pressure > 175 or diastolic > 104 mmHg
• heart disease
• serum calcium > 2.54 mmol/l
• history of renal stones