Glycosylated Hb (GHb) will be proportional to mean plasma glucose levels during the previous 6-12 weeks. It helps determine whether you are at an increased risk of developing diabetes, diagnose diabetes and prediabetes, and monitor long-term glucose control. Advantages to using HbA1c for diagnosis include: provides an assessment of chronic hyperglycemia, no fasting is necessary, and a single test can be used for both diagnosing and monitoring diabetes.