Hemoglobin is a substance within red blood cells that carries oxygen throughout your body. When the diabetes is not controlled, sugar builds up in the blood and combines with your hemoglobin, becoming "glycated." Therefore, the average amount of sugar in the blood can be determined by measuring a hemoglobin A1c level. If the glucose levels have been high over recent weeks, the hemoglobin A1c test values will be higher.
For people without diabetes, the normal range for the hemoglobin A1c test is between 4% and 5.6%. Hemoglobin A1c levels between 5.7% and 6.4% indicate increased risk of diabetes, and levels of 6.5% or higher indicate diabetes. The higher the hemoglobin A1c, the higher the risks of developing complications related to diabetes.
People with diabetes should have this test every three months to determine whether their blood sugars have reached the target level of control. Those who have their diabetes under good control may be able to wait longer between the blood tests, but experts recommend checking at least 2 times a year.