February 24, 2016

Understand Your HbA1c

The HbA1C test is known as the A1C test by most people. The A1C test measures the blood glucose level for the last four months. The prior month accounts for 50 percent of the A1C. The month prior to the last month accounts for 25 percent of the A1C, and the third and fourth prior months contribute the remaining 25 percent of the A1C value.

Doctors use the A1C value as a measure of how well you are managing your diabetes or not managing your diabetes. This is the reason we as patients need to use our meters to measure our daily blood glucose readings.

If you did not have diabetes, your typical A1C level would be about 5 percent. For people with diabetes, the experts can't agree on what the A1C target level should be. The American Diabetes Association (ADA) recommends an A1C target of less than or equal to 7 percent. The American Association of Clinical Endocrinologists (AACE) recommends a target of less than or equal to 6.5 percent.

Hemoglobin A, a protein found inside red blood cells, carries oxygen throughout the body. When there is glucose in the bloodstream, it can actually stick (glycate) to the hemoglobin A protein. More glucose in the blood means that more glucose sticks to hemoglobin, and a higher percent of hemoglobin proteins become glycated.

Once glucose sticks to a hemoglobin protein, it typically remains for the lifespan of the hemoglobin A protein — as long as 120 days. The A1C test measures how much glucose is actually stuck to hemoglobin A, or more specifically, what percent of hemoglobin proteins are glycated. Thus, having a 7% A1C means that 7% of the hemoglobin proteins are glycated.

This is where disagreement often comes into play. For people with well-managed type 2 diabetes, visits to the doctor may only be required twice a year. However, for those that have poorly managed diabetes or are on insulin (not that these people have poorly managed type 2 diabetes) probably will see their doctor at least four time per year. Always be prepared to see the doctor on a different schedule.

The A1C test, typically performed by a health care professional, often doesn’t hurt. Only a single drop of blood is needed, and the sample is either analyzed on-site or is sent to a laboratory for testing. Some doctors prefer doing the A1C test from a blood draw.

While the A1C is a good measure of overall glucose control, it cannot replace self-monitoring of blood glucose (SMBG). Like other tests, A1C results may vary from lab to lab. The A1C test is not calibrated the same everywhere, though an international effort is underway to standardize the A1C test to a new International Federation of Clinical Chemistry and Laboratory Medicine standard.

A1C results can be misleading when red blood cell survival is prolonged or reduced; some health conditions can result in falsely high A1c results (as in cases of anemia) or falsely low (as in cases of hemolysis). There are other factors that can affect the A1C results.

One piece of good news: When someone has his or her A1C checked, that person does not need to worry about fasting; food eaten on the same day won’t affect the score.

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