Diabetes Diary: The A1C Test

  • 2 Minutes Read

Find out what the A1C test is and why you should know about it. If you have been diagnosed with diabetes, then put this post on your must-read list. Includes helpful online resources.

Diabetes Diary: The A1C Test

The A1C test can screen for diabetes as well as to monitor diabetes control. Although you can measure A1C with a finger stick using purchased kits and meters, the most accurate method is to have a lab test it using a blood draw. The A1C test measures the percentage of "glycosylated" (sugared) hemoglobin molecules in your blood and appears to be an accurate way to assess estimated average blood glucose (eAG) over a 2-3 month period. See this chart from the American Diabetes Association for a comparison of A1C and corresponding estimated average glucose values.

A1C & Diagnosing Diabetes

There are three tests that can be used to diagnose diabetes or prediabetes: A1C, fasting glucose, or the oral glucose tolerance test (OGTT).I like the A1C test for diagnosis since it is convenient (one non-fasting blood draw) yet thorough - it captures blood glucose that is rising too high from either the overnight fast and/or from meals. Technically, you could argue that the OGTT is the best since it identifies both high fasting and/or post-meal rises in blood glucose, but it is also more expensive and a nuisance to do it. You have to arrive at the lab in the fasting state and then stay there for 2- 3 hours. And drinking the test solution can be nauseating - it contains between 75 - 100 grams of glucose.

The chart below displays the American Diabetes Association's diagnostic ranges for A1C and fasting glucose. If you live outside of the United States, then please use your country's diagnostic ranges. If you like pictures then take a look at this one - it compares A1C, fasting glucose, and OGTT test values for diagnosis.

A1C Fasting Glucose
Prediabetes 5.7% to < 6.5% 100 mg/dL to < 126 mg/dL
Diabetes >=6.5% >= 126 mg/dL

A1C Goal

The A1C goal for minimizing risk of diabetes complications (especially for the kidneys, eyes, and nerves) as well as risk for hypoglycemic episodes (low blood sugar) is typically less than 7%. However, your doctor might set a higher or lower A1C goal that is individualized based upon your medical history. It is important to discuss concerns with your doctor and follow his/her recommendations. If your A1C has dropped but with the side effect of increased hypoglycemic episodes - you could be doing more harm than good as hypoglycemia itself carries increased risk.

How Often to Test

Most organizations recommend testing A1C every 3 months if A1C is above goal. Once goal is reached, it is typical to test every 6 months. Your doctor might recommend a different A1C testing plan so please follow what he/she recommends.

If you have prediabetes, then most organizations screen yearly. However, your doctor might have reason to test earlier than that based upon your medical history.

A1C & Anemia

Both the hemoglobin/red blood cell concentration in the blood as well as blood glucose control will affect the A1C value. Iron deficiency anemia will cause a low A1C value so it will not be an accurate reflection of your diabetes control nor will it accurately screen for prediabetes or diabetes. It is important to treat anemia for health reasons anyway, but especially important for diagnosis or monitoring of diabetes.

There's an app for that!

MyNetDiary's Diabetes Tracker is an iPhone app that integrates their powerful food and exercise tracker with blood glucose tracking. This is my favorite iPhone app - and if you have diabetes then I urge you to consider trying it. For more information on what the tracker can do and how to use it, please read "Tracking Diabetes with MyNetDiary."

Optimizing Control

For one-on-one or class-based diabetes self-management training, ask your doctor for a referral to a diabetes clinic or to a certified diabetes educator (CDE). CDEs are typically also nurses, dietitians, or pharmacists and they can help you with customized meal plans as well as skills related to using insulin, testing blood glucose, or simply adhering to your diabetes medication schedule. Medicare covers this type of care but check with your state if you have Medicaid or check your benefits if you have private health insurance.

More Online Resources

American Diabetes Association

Joslin Diabetes Center

Kaiser Permanente: Living Healthier with Diabetes

MyNetDiary: Diabetes Basics

National Diabetes Information Clearinghouse: The A1C Test and Diabetes>

Diabetes->Blood glucose
May 7, 2013
Katherine Isacks
Katherine Isacks, MPS, RDN, CDE - Registered Dietitian and Certified Diabetes Educator (CDE)

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