Animal and human studies have shown an association between serum 25-hydroxyvitamin D (25(OH)D) level and insulin secretion and sensitivity. Accordingly, an association between 25(OH)D and glycated haemoglobin (HbA(1c)) is to be expected, and this was tested for in the present study. The Tromsø Study is a longitudinal population-based study initiated in 1974. In the sixth Tromsø Study conducted in 2007-2008, 12,984 subjects aged 30-87 years attended. After exclusion of current smokers and subjects with diabetes, the dataset consisted of 8643 subjects available for the present analyses. The correlation between serum 25(OH)D and HbA(1c) was -0.07 (p