World wide the prevalence of type 2 diabetes is increasing and 30-50% of patients are undiagnosed. Early detection and intervention may decrease the risk of late diabetic complications, and thus clear guidelines for early detection and diagnosis of type 2 diabetes are needed. We recommend those individuals with either previous gestational diabetes; obesity (BMI > 30 kg/m2) and/or two or more relatives with diabetes should be considered eligible for testing for diabetes. In order to make the diagnosis two diabetic glucose values on separate days are required. The diagnosis may be made using plasma glucose or capillary whole blood, but quality control measures are essential for glucose measurements in general practice as well as in departments of clinical biochemistry.