The trials and tribulations of determining HbA targets for diabetes mellitus.

Glycated haemoglobin (HbA) is considered the gold standard for predicting glycaemia-associated risks for the microvascular and macrovascular complications of diabetes mellitus over 5-10 years. The value of HbA in the care of patients with type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM) is unassailable, yet HbA targets remain contentious. Guidelines from diabetes care organizations recommend conflicting HbA targets - generally between 6.5% and 8%. However, all such organizations advocate for individualization of HbA targets, leaving both health-care providers and their patients confused about what HbA target is appropriate in an individual patient. In this Review, we outline the landmark T1DM and T2DM trials that informed the current guidelines, we discuss the evidence that drives individualized HbA targets, we examine the limitations of HbA, and we consider alternatives for monitoring glycaemic control. Ultimately, in synthesizing this literature, we argue for an HbA target of <7% for most individuals, but emphasize the importance of helping patients determine their own personal goals and determinants of quality of life that are independent of a particular glycaemic target. We also recognize that as newer technologies and anti-hyperglycaemic therapies emerge, glycaemic targets will continue to evolve.