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Hemoglobin A1c (HbA1c) (cont.)

How Is HbA1c Measured?

A chemical (electrical) charge is present on the molecule of HbA1c, and the amount of the charge differs from the charges on the other components of hemoglobin. The molecule of HbA1c also differs in size from the other components. HbA1c may be separated by charge and size from the other hemoglobin A components in blood by a procedure called high pressure (or performance) liquid chromatography (HPLC). HPLC separates mixtures (for example, blood) into its various components by adding the mixtures to special liquids and passing them under pressure through columns filled with a material that separates the mixture into its different component molecules.

HbA1c testing is done on a blood sample. Because HbA1c is not affected by short-term fluctuations in blood glucose concentrations, for example, due to meals, blood can be drawn for HbA1c testing without regard to when food was eaten. Fasting for the blood test is not necessary.

What Are Normal Levels of HbA1c?

In healthy people, the HbA1c level is less than 6% of total hemoglobin. A level of 6.5% signals that diabetes is present. Studies have demonstrated that the complications of diabetes can be delayed or prevented if the HbA1c level can be kept below 7%. It is recommended that treatment of diabetes be directed at keeping an individual's HbA1c level as close to normal as possible (<6%) without episodes of hypoglycemia (low blood glucose levels).

What Are High Levels of Hemoglobin A1c?

As mentioned previously, normal levels of HbA1c are less than 6%, so a measurement over 6% is considered high. For many people with type 1 and type 2 diabetes, the goal is to keep the HbA1c levels under 7%, since keeping levels below 7% has been shown to delay the complications of diabetes.

Many laboratories report a calculated eAG (estimated average glucose) along with every HbA1c results. This is a correlation of the HbA1c levels with the average blood sugar level. For example, a HbA1c measurement of 7% corresponds to an eAG measurement of 154 mg/dl.

The American Diabetes Association has a calculator to help you convert your A1c level to the average blood glucose level (http://www.diabetes.org/living-with-diabetes/treatment-and-care/blood-glucose-control/a1c/).

Medically Reviewed by a Doctor on 2/29/2016

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