The glycated hemoglobin (HbA1c) test shows the subject’s average blood glucose level over the past 2 to 3 months.
People with diabetes need to have this test regularly to see if their blood glucose levels are staying within normal limits. This test can determine whether diabetes medications need to be adjusted. A glycated hemoglobin test is also used to diagnose diabetes.
What is hemoglobin?
Hemoglobin is a protein found in red blood cells that gives blood its red color and serves to carry oxygen throughout the body.
How glycated hemoglobin is measured
The sugar in the blood is called glucose. When glucose accumulates in the blood, it binds to the hemoglobin in the red blood cells. The glycosylated hemoglobin test measures the amount of glucose bound to hemoglobin.
Hemoglobin lives for about 3 months, so a glycosylated hemoglobin test shows the average level of glucose in the blood over the past 3 months.
If blood glucose levels have been consistently high in recent weeks, the glycosylated hemoglobin level test may be higher.
| Glycosylated hemoglobin (%) | Average blood glucose level (mg/dl) |
| 4 | 68 |
| 5 | 97 |
| 6 | 126 |
| 7 | 152 |
| 8 | 183 |
| 9 | 212 |
| 10 | 240 |
| 11 | 269 |
| 12 | 298 |
| 13 | 326 |
| 355 |
What is a normal glycated hemoglobin test result?
For non-diabetic patients, the normal range for glycosylated hemoglobin levels is between 4% and 5.6%. A glycosylated hemoglobin level between 5.7% and 6.4% indicates an increased risk of diabetes. 6.5% and higher levels of glycosylated hemoglobin indicate diabetes.
Glycosylated hemoglobin targets for people with diabetes
The target glycated hemoglobin level for people with diabetes is usually less than 7%. The higher the glycosylated hemoglobin level, the higher the risk of developing diabetes-related complications.
A combination of diet, exercise, and medication treatment strategies can help lower blood glucose levels.
People with diabetes should have a glycosylated hemoglobin test every 3 months to make sure their blood glucose is within the target range. For people with well-controlled diabetes, the interval between tests may be extended, but experts recommend at least 2 tests per year.
There may be errors in glycated hemoglobin results in patients with hemoglobin-related disorders, such as anemia. Other factors that may affect glycated hemoglobin results include vitamin C and E supplementation and high cholesterol levels. Kidney disease and liver disease may also affect the results.