Strong
HbA1c
Glycated haemoglobin reflects average blood glucose across roughly the preceding two to three months, which makes it considerably harder to game than a single fasting glucose taken after a careful week. Chronic hyperglycaemia glycates proteins throughout the body, driving microvascular damage in the retina, kidney and nerves as well as macrovascular disease.
Why it grades Strong
The global diagnostic and monitoring standard for diabetes. The DCCT and UKPDS trials established that glycaemic control reduces microvascular complications, and the WHO and ADA diagnostic thresholds are built directly on that evidence base.