A key long-term marker in diabetes control is HbA1c (glycated or glycosylated haemoglobin). The higher this number, the less well controlled the diabetes is. Much of the data surrounding management of type 2 diabetes in the UK is provided by the UK Prospective Diabetes Study (UKPDS), which observed adults with type 2 diabetes over a 20-year period. 

The UKPDS study showed that for every one per cent reduction in HbA1c, there was a 35 per cent reduction in microvascular complications and a 25 per cent reduction in deaths from diabetes. It also showed that early diagnosis and more aggressive treatment of blood glucose levels is associated with better clinical outcomes.