The HbA1c test is a laboratory test, which indicates blood glucose control over last three months. HbA1C is formed when glucose in the blood binds irreversibly to hemoglobin to form a stable glycated hemoglobin complex. Since it is irreversible, it stays through out the life span of red blood cells i.e. 90-120 days. Therefore HbA1c testing serves as a reliable indicator of overall glucose control of previous 90 days.
Monitoring HbA1C allows doctor to assess long-term compliance with management protocols, such as diet, exercise and medication. The test shows whether the blood glucose is close to normal or too high. An HbA1c test result between 4 to 6 % is considered normal. HbA1C value less than 7% in a diabetic means blood glucose is under control. A change in a treatment plan is almost always needed if the test result is over 8%. Studies conducted in people with diabetes have shown that lower the HbA1c number, greater the chance of staying healthy & will slow or prevent the development of serious eye, kidney and nerve disease.
People with diabetes should get the HbA1C test at least two times a year if their blood glucose is in the target range and stable. If they are taking insulin, if their treatment changes or if their blood glucose stays too high, they should get the HbA1C test at least every 3 months until their blood glucose level improves.
It is important to note that HbA1c testing is not considered as replacement of blood glucose testing. The blood glucose test is a real-time measurement of glucose, while the HbA1C test value gives an idea of average blood glucose levels over preceding 3 months.
When interpreting the test one should keep in mind that results differ depending on the test method used. Some labs measure hemoglobin A1 (which is different from hemoglobin A1c).