What is HbA1c and why does it matter?

It reflects average blood glucose over roughly the previous three months by measuring glycated haemoglobin. It's less affected by day-to-day fluctuation than single readings, making it the standard for diagnosis and long-term control.

It can be misleading in anaemia, recent blood loss or transfusion, haemoglobin variants, and chronic kidney or liver disease — situations where fasting glucose is more reliable.

A 1% reduction in HbA1c is associated with meaningful reductions in microvascular complications, which is why it is used to track treatment.