Measuring Your Hemoglobin A1C for Average Blood Sugar

Know Your Average Blood Sugar With An AIC Test

Diabetic testing
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Your average blood sugar can be measured by a hemoglobin A1c test. Knowing your average blood sugar is a vital part of managing your type 1 diabetes. The hemoglobin A1c test, also commonly referred to as A1c, is a measure of your blood sugar control over the past 2 to 3 months. Here’s a brief overview of the most frequently asked questions about the A1c test:

How does the A1c test measure the level of blood sugar?

To understand how the test works, we need to first learn about hemoglobin. Hemoglobin is the part of red blood cells that carry oxygen to all parts of our body. Some of the sugar that ends up in our bloodstream from the food we eat attaches to hemoglobin and stays there for the life of the red blood cell, which is usually no longer than 3 months. If you have elevated levels of sugar in your blood, as many with diabetes do, then more sugar will attach to your red blood cells over the short life of those cells. A simple blood test measures the amount of sugar in percentages.

How is the A1c test performed?

This test requires a small sample of blood and is usually done in your doctor’s office. The sample is sent to a lab for testing and the results are sent to your doctor. Home testing kits for A1c are now available. Though there is some concern among professionals that these home tests are not as accurate as those done in a lab, many people who use them find them helpful. Home testing is inexpensive and can give you important information about your management between doctor’s visits.

How do I interpret the results of an A1c test?

Everyone, regardless of whether they have diabetes, has some sugar attached to their red blood cells. A person without diabetes would typically have a hemoglobin A1c test of around 5%. Those with type 1 diabetes can have an A1c test result that is much higher -- upwards of 25% if their diabetes management is poor. Ideally, the goal is to have an A1c test below 7%. A result of 8% or more is a sign that changes need to be made to better manage glucose levels.

Why is managing my blood sugar so important?

The findings of the Diabetes Control and Complications Trial (DCCT) have conclusively shown that people with diabetes who manage their blood sugar well with A1c levels close to 7% can delay the onset or possibly even prevent diabetes-related complications that affect the eyes, kidneys, and nerves. The DCCT showed that even an A1c of 8% significantly increased the risk of these complications.

The American Diabetes Association is now promoting a new term called estimated Average Glucose (eAG) that more accurately helps you convert your A1c test result into a number that corresponds to your glucose meter in mg/dl. For example, if your A1c test came back at 7.8%, that would convert to an estimated Average Glucose of 177 ml/dl. You can view a handy chart or do your own conversion of your A1c test result at their site.

How often should an A1c test be done?

You should have an A1c test performed immediately after diagnosis and then at least twice a year. Many endocrinologists recommend that those with type 1 diabetes have this test done every 3 months. That corresponds to the typical lifespan of red blood cells and gives you a continuous picture of your diabetes management.

Can the A1c test be a substitute for daily testing?

The A1c test should be used in addition to your daily blood sugar testing. The A1c is only an average of what your blood sugar has been over the last three months. The only way you know for certain what your blood sugar level is at any given time is to test. So, it is still important that you test your blood several times each day for effective management.


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  • A1C Test. American Diabetes Association. Accessed December 19, 2008.