A1C
Also called: HbA1c
Clinical reviewer: Jacob Moore, MD · Last checked September 24, 2026
What is A1C?
A1C is a blood test that measures your average blood glucose level over the past 3 months, based on glucose attaching to hemoglobin in red blood cells. Also called HbA1c, glycated hemoglobin, or glycohemoglobin, it is used to diagnose type 2 diabetes and prediabetes, and is the primary test for diabetes management. Results are reported as a percentage.
How is A1C tested and read?
A1C measures how much glucose has attached to hemoglobin in red blood cells, giving an average of your blood glucose level over about the past 3 months [1]. No fasting is needed before the blood draw [1]. Results are reported as a percentage and grouped into ranges:
| Result | A1C |
|---|---|
| Normal | Below 5.7 percent |
| Prediabetes | 5.7 to 6.4 percent |
| Diabetes | 6.5 percent or above |
The higher the percentage, the higher your blood glucose levels have been [1]. Any test used to diagnose diabetes needs confirmation with a second measurement, unless there are clear symptoms of diabetes [1].
Why does A1C matter for GLP-1 treatment?
Ozempic and Mounjaro are indicated to improve glycemic control in adults with type 2 diabetes [2][3], and A1C is the primary test used for diabetes management [1]. The test is also used to diagnose type 2 diabetes and prediabetes [1]. Although A1C reflects about 3 months, blood glucose levels within the most recent 30 days have a greater effect on the reading than earlier months [1]. Experts recommend that people with diabetes have an A1C test at least twice a year [1].
Frequently asked questions
Does A1C require fasting?+−
No. A1C does not require fasting before the blood draw, so it can be measured at any time.
How often should people with diabetes get an A1C test?+−
Experts recommend that people with diabetes have an A1C test at least twice a year, since it reflects blood glucose control over time.
Related terms
Sources
This entry is for education and is not medical advice. Talk with a licensed clinician about your own situation before starting, stopping, or changing any treatment.
