The A1C test can be used to diagnose diabetes or help you know how your diabetes treatment plan is working.
The A1C test gives you a picture of your average blood glucose level over the past 2 to 3 months. This lets you understand your levels over a longer period of time compared to the results from your blood glucose meter or continuous glucose monitor (CGM).
In some ways, the A1C test is like a basketball player's shooting percentage: It tells you how often you’re reaching your goal. A single blood test result and a basketball player’s single shot can’t tell you how often a goal is being reached over time. A basketball player knows they can’t make every shot they take—their goal is to try to make as many as possible. When you’re managing diabetes, you shouldn’t expect to reach your targets all the time, but you want to reach them as much as you can. The A1C test tells you how you’re doing.
When glucose enters your blood stream, it attaches to a protein in your red blood cells called hemoglobin. When you have higher blood glucose levels, there is a higher number of hemoglobin with glucose attached. The A1C test checks your red blood cells for the percentage of hemoglobin with glucose attached (glycated). Because your red blood cells regenerate around every three months, the A1C test gives you an idea of what your blood glucose levels have been over that amount of time.
The A1C test can also be referred to as a hemoglobin A1C or HbA1c test.
The A1C is a simple blood test. It can be a finger prick at the doctor’s office or might be part of a lab test. Your doctor will tell you how often you need the A1C test, but if you’re living with diabetes, you’ll have the test at least twice a year. You may have it more often if your treatment plan has changed or isn’t working as expected.
Monitoring your blood glucose at home and your A1C results are two key parts of managing diabetes. Both give you information about your blood glucose levels and if your treatment plan is working.
When you use a blood glucose meter (BGM) or a continuous glucose monitor (CGM), you’re getting information about your blood glucose level at that moment (CGMs give you more information along with it). This allows you to make choices to manage it based on your treatment plan. It also can highlight if there’s an ongoing issue at a specific time during your day or week.
Your A1C offers a big picture of how your blood glucose has been over time. This allows you and your healthcare team to talk about if changes to your treatment plan are needed. These could be changes to your eating plan, physical activity, emotional support, or the medications you take. Reaching your A1C targets is one way to lower your risk of developing diabetes complications.
For most people living with diabetes, an A1C of 7% or less is the recommended target. Your A1C target will be based on your needs and goals.
A1C test results are reported as a percentage. The higher the percentage, the higher your blood glucose levels have been over the past 2 to 3 months. Your A1C result can be shown as estimated average glucose (eAG) using mg/dL, the same way you see the result of your blood glucose checks.
If your lab test results or your healthcare team haven’t given you your eAG, you can use the following calculator or chart to get your eAG based on your A1C results. You can also see which A1C would give you a different eAG.
| A1C | eAG |
|---|---|
| % | mg/dL |
| 6 | 126 |
| 6.5 | 140 |
| 7 | 154 |
| 7.5 | 169 |
| 8 | 183 |
| 8.5 | 197 |
| 9 | 212 |
| 9.5 | 226 |
| 10 | 240 |
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