I just went elsewhere on this site and it said this.......
HbA1c as a diagnostic test
The HbA1c test may also be used as a way of diagnosing diabetes, particularly type 2 diabetes. The test is useful as it is affected less by short term issues such as illness, which can temporarily increase blood glucose levels.
The World Health Organisation (WHO) suggests the following diagnostic guidelines:
HbA1c below 42 mmol/mol (6.0%): Non-diabetic
HbA1c between 42 and 47 mmol/mol (6.0–6.4%): Impaired glucose regulation (IGR)
HbA1c of 48 mmol/mol (6.5%) or over: Type 2 diabetes