An HbA1c blood test is a test which looks at how much sugar your red blood cells have been exposed to in the last 3 months. It is useful as it tell you about your average sugar level rather than a finger prick test which just tells you what your sugar level is right there and then. The results are related but not directly e.g. an HbA1c of 48mmol/mol suggests an average sugar level of around 7.8mmol/L. HbA1c can be used to diagnose Pre-Diabetes or Diabetes as shown in the illustration. If you have no symptoms (e.g. thirst, weight loss) then two readings of 48 or above are needed to make a diagnosis of Type 2 Diabetes.