HbA1c (Glycated Hemoglobin)
Definition
Measures, as a percentage, how much of the hemoglobin in red blood cells is coated with glucose (sugar). Because red blood cells live for about three months, this test reflects the average blood sugar level over the past 2 to 3 months. It is not affected by daily fluctuations.
Purpose
Used for screening and diagnosis of type 2 diabetes and prediabetes. In people with diabetes or prediabetes, it allows monitoring of blood sugar control and the effectiveness of treatment.
Results
American Diabetes Association (ADA) diagnostic thresholds:
| HbA1c | Interpretation |
|---|---|
| Below 5.7% | Normal |
| 5.7% to 6.4% | Prediabetes |
| 6.5% and above | Diabetes |
Normal Values
Below 5.7%. However, the individual target value varies with age and general health status; you should discuss your target with your physician.
Risks and Limitations
The risk of the blood draw is very low. The main limitation of the test: its reliability decreases in conditions that affect red blood cells, such as anemia, blood disorders, kidney failure and liver disease. It cannot be used to diagnose gestational diabetes (pregnancy diabetes) or type 1 diabetes. In addition, the diagnostic performance of HbA1c differs between ethnic groups; international guidelines (WHO, EASD, ADA, IDF, Diabetes UK) diverge from one another in their definition of prediabetes.