HbA1c

HbA1c or Glycated hemoglobin is a form of hemoglobin that is chemically linked to a sugar. Most monosaccharides, including glucose, galactose and fructose, spontaneously (i.e. non-enzymatically) bond with hemoglobin, when present in the bloodstream of humans. However, glucose is less likely to do so than galactose and fructose, but, because it is present in significant amounts, it is the main sugar that binds to hemoglobin.

Overview

HbA1c is a commonly used indicator of the average blood sugar levels for the past three months before the measurement. It is formed in a non-enzymatic pathway by hemoglobin's exposure to plasma glucose. It is a measure of the beta-N-1-deoxy fructosyl component of hemoglobin. The HbA1c fraction is proportional to blood glucose concentration over an entire RBC lifespan (120 days, average).

Medical Use

HbA1c is a standard tool to determine blood sugar control for patients with diabetes. It is given in percentages. Normal levels are below 5.7%. Levels from 5.7% to 6.4% indicate increased risk of diabetes, and levels above 6.5% are indicative of diabetes.

Measurement

HbA1c is measured primarily to identify the three-month average plasma glucose concentration and thus can be useful for the management and potential adjustment of therapy for patients with diabetes.

Limitations

There are some clinical conditions in which the HbA1c value may be an unreliable indicator of average blood glucose levels. These include conditions with altered red cell turnover such as anemia, hemolysis, and heavy bleeding.

See Also

• Diabetes
• Blood Sugar
• Hemoglobin

HbA1c Resources
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