Hemoglobin Never Forgets: Managing your diabetes with the A1C test

An A1C test measures how high your blood-glucose levels have been over a 2-3 month period by analyzing hemoglobin. Hemoglobin is a small protein that lives in the red blood cells of your body and carries the memory of any glucose it encounters in the blood stream for the three months of the blood cell’s life.

The A1C test is an excellent general indicator of how well you have controlled your blood sugar over an extended period of time. It can be used to help you and your health care team better manage your diabetes. The test is also known as HbA1c, glycohemoglobin, glycated hemoglobin, glycosylated hemoglobin, GHb and diabetic control index.

The A1C test works by measuring the amount of blood glucose in the hemoglobin. Hemoglobin is a protein in the red blood cells that carries oxygen from the lungs to all the cells in the body. If a person has diabetes, excess glucose enters the red blood cells and attaches itself to the hemoglobin; this is called glycosylation.

Imagine the glucose as a foreigner lost in a strange city (the red blood cells) who has to cling to a local (the hemoglobin) to find its way around. The more glucose there is in the blood, the more hemoglobin is glycated by glucose. The glucose stays with the hemoglobin until the red blood cell dies after 2-3 months. In the A1C blood test, hemoglobin is drawn out of the body in a blood sample and analyzed to see how much of it has been glycated: the results indicate how high your glucose levels have been for the past three months.

Another way to understand it is to think of your red blood cells as score keepers remembering the number of “glucose hits” to the hemoglobin. An A1C test is like a three month print-out of this score board. When you read the score board you can tell how high your blood-glucose levels are based on the amount of glucose-containing hemoglobin. If you have a high blood-glucose level, you will have a “high scoring” A1C.

The A1C test is a simple blood test in which a blood sample is drawn, usually from a vein in the arm, and examined in a laboratory. Unfortunately, different laboratories use slightly different numbers to display results, but your doctor should be aware of this; ask your doctor to fully explain results for you and make sure any comparison of past results uses a consistent results scale.

You can also test your A1C level at home using an over-the-counter test approved by the FDA. This test requires a prescription. Ask your doctor for further information if you are interested.

An A1C test should be done initially when you are diagnosed with diabetes. After the first test, the American Diabetes Association recommends the following schedule:

• If you have Type 2 diabetes and do not use insulin, and your blood sugar is well controlled, test twice a year.
• If you have Type 1 diabetes or Type 2 diabetes and use insulin, test every three months.
• If you change treatment, test every three months.

The test results are given in the form of a percentage; this percentage indicates the amount of hemoglobin that is glycated. Normally, 3-6 percent of hemoglobin is glycated, but in people with uncontrolled diabetes the figure can be anywhere between 6-20 percent.

The following table translates A1C results into an average daily blood glucose level and shows what sort of blood glucose control various A1C percentage results indicate.

Most doctors aim to keep the A1C levels for people with diabetes below 8.5 percent and ideally around 7 percent or less. Results higher than 7 percent indicate that your average blood glucose levels are too high. This can be due to too little exercise, too little insulin or diabetes medicine, too much food, the wrong kind of food, stress, illness, or infection.

Though daily blood-glucose testing provides you with the best way to examine your levels day-to-day, the tests cannot give you a long-term picture of the effectiveness of your diabetes management program. Daily blood-glucose readings are also affected by the time of day or the meals you have eaten. However, the A1C test provides you with a reliable measurement of how you are managing your blood glucose levels in the long term. The test can also:

• Provide you with feedback on your current treatment strategy. If results indicate that your levels are too high, you should make treatment changes to improve your diabetes management and quality of life, and prevent or delay the onset of health complications.

• Act as a “back-up” to daily self-testing. Sometimes daily testing is not accurately performed. The A1C test provides another measure to compare daily tests against. If you are not self-testing correctly, the results will be inconsistent and you will know to alter your daily testing routine.

• Alert you to health complications. High blood sugar equates to a high risk of developing diabetes-related complications such as vision loss, kidney damage, nerve damage, heart disease, stroke, and gum disease. For each one percent reduction in A1C level, your risk of complications drops by 25 percent.

• Help you to feel better. The benefits of the test all culminate to provide you with better control of your diabetes, therefore helping you to feel well, and live a healthier life.

It is very important to remember that the A1C test in no way replaces daily self-testing of blood glucose. The A1C does not test your daily blood glucose control. Daily testing is crucial for knowing whether or not to adjust medications or other treatment, and for warning you of any emergency situations in your blood glucose levels.

Blood sugar checks and log results are highly important for effective control. However, the A1C test is an excellent additional resource to help better manage diabetes. If you are not currently taking this test and believe you could benefit from it, make sure you talk to your health care team about starting.