The number of people with diabetes in the UK is almost 1.8 million and this is continuing to rise, according to recent figures. But only about half of these are currently diagnosed. It is obviously essential to ensure that these people are diagnosed as early as possible and then managed appropriately to ensure they receive the best possible care to minimise long-term complications. In this article, we review how to diagnose diabetes accurately, based on good practice recommended in standard two of the National Service Framework (NSF) for Diabetes. What should we be measuring in people who present with the classic symptoms and in those who do not to ensure an accurate diagnosis of diabetes?