The A1c value reflects median glycemia over roughly 3 months. The performance of the test is generally excellent, and it is the primary tool for assessing glycemic control. In addition, A1c has a strong predictive value for diabetes complications, highlighting its importance in the initial assessment and routine care of patients with diabetes.
However, the A1c test is an indirect measure of average glycemia and thus is subject to limitations. For example, conditions that affect red blood cell turnover (eg, hemolytic and other anemias, glucose-6-phosphate dehydrogenase deficiency, recent blood transfusion, use of drugs that stimulate erythropoiesis, end-stage kidney disease, and pregnancy) may lead to incongruities between the A1c result and the patient's true mean glycemia, per the ADA.
Hemoglobinopathies, such as sickle cell trait, may distort A1c levels. Clinicians should also consider hemoglobin variants, especially when the A1c result does not correlate with the patient's CGM or BGM levels. Though a certain amount of variability in the relationship between average glucose levels and A1c exists among individuals, mean glucose and A1c generally correlate with one another over time.
Learn more about blood glucose monitoring in patients with diabetes.
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Cite this: Anne L. Peters. Fast Five Quiz: Type 2 Diabetes and Glucose Monitoring - Medscape - Dec 20, 2022.