Blood sugar (glucose) tends to bind to different proteins, including hemoglobin and albumin. HbA1c or glycated hemoglobin represents the fraction of the hemoglobin that reacted with the glucose. Given that blood hemoglobin is continuously renewed, the percentage of HbA1c represents the average glycemia (blood glucose level) during the 4- to 6-week period prior to collection. HbA1c is therefore very useful in diagnosing and monitoring diabetes. HbA1c levels are not affected by food intake.
An HbA1c level equal to or greater than 0.065 (6.5%) is consistent with a diabetes diagnosis. An HbA1c level between 0.060 and 0.065 (6.0 and 6.5%) is consistent with “pre-diabetes” and indicates an increased risk of cardiovascular disease. An abnormally low level most often indicates an abnormal hemoglobin fraction that is interfering with the measurement.
Measuring HbA1c levels is recommended every three to six months in patients being treated for diabetes. Treatment targets are to bring HbA1c levels back down as close to normal as possible (below 0.065), but they are adjusted according to different variables, such as the patient’s age, treatment type and risk of hypoglycemia.