Your hemoglobin A1C test measures the average of your blood glucose, commonly referred to as your blood sugar. The A1C levels are measured by looking at glucose that is bound to a protein in your red blood cells. The average lifespan of one of your red blood cells is 120 days. The A1C test looks at all the red blood cells in the sample being tested, but the result is weighted toward your glucose levels over the last 30 days having more influence on the A1C number than older levels. Not much new information would be gained by repeating the test more often than four times per year. However, your doctor may recommend it be done less often.
Why You Need A1C Testing
If you have diabetes, the goal is to keep your blood glucose levels as normal as possible for the long term. You should test daily with a glucometer, but the results are more of a spot check based on the time you took the sample while the A1C levels are an average for your blood glucose over time. Your A1C level converts to a daily average for your blood glucose. For example, the American Diabetes Association recommends A1C levels of no higher than 7.0, which converts to a daily average of 154 mg/dl.
Why Glucometer Results Are Not Enough
You probably have been advised to test using a glucometer just before meals and two hours after. This is preprandial and postprandial testing. Your doctor may have also wanted some early morning testing results and maybe a few from the middle of the night. This helps your doctor know trends of when your blood glucose is high or low.
If your doctor relied only on a single result to adjust your therapy, the result would not tell the whole story of your diabetes. A single result showing a high after a meal with lots of carbohydrates or a low because you did not eat and exercised would lead to inaccurate treatment. The A1C test shows a broader picture of your daily control.
Why Glucometer Testing Helps Lower A1C Levels
Unfortunately, there are too many people with Type 2 diabetes who are on oral medications but do not do multiple daily tests using a glucometer. This can lead to higher A1C test results due to times of the day your blood glucose is running high when it could be better controlled. Dawn phenomena is when your blood glucose spikes in the early morning hours. You may be having high blood glucose levels a couple of hours after a meal, or you may be having slight hypoglycemia after exercise.
The A1C test does not reveal any of this. In fact, hypoglycemic episodes can skew the A1C test to make it appear lower than it actually is. Daily testing using a glucometer gives the entire picture when used with the A1C test.
If you have diabetes, you should have an A1C test performed every three months. If your doctor is only recommending a twice annual test, you should inquire as to the reason. Part of it may be due to your enthusiasm and willingness to controlling your blood glucose levels to delay or prevent the onset of complications caused by high blood glucose. Your willingness and commitment to following dietary and exercise recommendations and daily testing with a glucometer shows your doctor that you will do your part in controlling diabetes. This makes the A1C test valuable to you and your doctor.