Brown adipose tissue has the capacity to consume large amounts of energy and has insulin-independent glucose uptake. The investigators have recently observed an inverse correlation between irisin levels and insulin needs of type 1 diabetes patients. Transplantation of brown adipose tissue to insulin-deficient rats normalized their blood glucose levels.

In this study 12 patients with long-standing type 1 diabetes (>10 years) and with variable exogenous insulin needs will be investigated for amount of brown adipose tissue with positron emission tomography using the tracer 18F-deoxy glucose.

Inclusion Criteria:

1. Adult patients (18 years of age or more)
2. Type 1 diabetes diagnose for more than 10 years

Exclusion Criteria:

1. Ongoing pregnancy
2. Ongoing breast-feeding
3. BMI<19
4. BMI >30
5. P-creatinine <110 µmol/l