What the A1c test measures
The A1c test measures your average blood sugar level over the past two to three months. Unlike a regular blood sugar test that shows what your blood sugar is at that exact moment, the A1c sticks around in your red blood cells and gives doctors a longer picture of how well your body has been managing glucose.
The test is also called hemoglobin A1c or glycated hemoglobin. When glucose stays in your bloodstream too long, it attaches to hemoglobin — a protein in red blood cells. The A1c percentage tells your doctor what fraction of your hemoglobin has glucose stuck to it. A higher percentage means your blood sugar has been running higher on average.
Key Takeaways
- The A1c test shows your average blood sugar over two to three months, not just at one moment in time.
- An A1c below 5.7% is considered normal; 5.7% to 6.4% suggests prediabetes; 6.5% or higher typically means diabetes, though your doctor will confirm with a second test.
- Doctors use A1c results to diagnose diabetes, monitor how well diabetes treatment is working, and catch blood sugar problems before they cause damage.
- You do not need to fast before an A1c test, and results usually come back within a few days.
- If your A1c is high, talking with your doctor about diet, exercise, weight, and medication can help bring it down over time.
Why your doctor orders an A1c test
Doctors order A1c tests for three main reasons: to screen for diabetes or prediabetes, to diagnose diabetes, or to see how well diabetes treatment is working. If you are over 45, your doctor may recommend an A1c test as part of routine screening even if you have no symptoms. If you have risk factors — family history of diabetes, overweight, high blood pressure, or heart disease — screening may start earlier.
The A1c is also useful for people already diagnosed with diabetes. Your doctor will order it periodically (often once or twice a year) to check whether your current treatment plan — diet, exercise, medication, or a combination — is keeping your blood sugar in a safe range. If your A1c is creeping up, it signals that adjustments may be needed.
Understanding your A1c results
A1c results are reported as a percentage. The ranges are:
- Below 5.7%: Normal blood sugar
- 5.7% to 6.4%: Prediabetes (higher than normal but not yet diabetes)
- 6.5% or higher: Diabetes (though your doctor will usually order a second A1c test or a fasting glucose test to confirm)
These cutoffs are the standard used by the American Diabetes Association and most U.S. doctors. If you have diabetes, your doctor will set a personal target A1c for you — often 7% or lower, though some people aim for different targets depending on age, other health conditions, and risk of low blood sugar.
Keep in mind that the A1c test is not perfect. It can be thrown off by certain blood disorders, kidney disease, liver disease, or recent blood transfusions. If your A1c result seems out of step with your home blood sugar readings or your symptoms, mention that to your doctor — they may order a different test to double-check.
What to expect during the test
An A1c test is a straightforward blood draw, usually done in a lab or your doctor's office. You do not need to fast beforehand or avoid food or drink — you can eat and drink normally that day. The phlebotomist will draw a small amount of blood from a vein in your arm, usually into one tube.
The test itself takes just a few minutes. You may feel a brief pinch when the needle goes in, but there is no pain during the draw. Results typically come back within a few days, though some labs return them within 24 hours. Your doctor's office will contact you with the result, or you may see it in your patient portal if your health system has one.
How to lower your A1c if it is high
If your A1c is above your target, the first step is talking with your doctor about what might help. For many people, changes in diet and physical activity can bring A1c down over time. Eating fewer refined carbohydrates and sugary foods, choosing whole grains and vegetables, and moving your body most days of the week all help your body use insulin better and keep blood sugar more stable.
Losing weight — even 5% to 10% of your body weight — can improve blood sugar control. If diet and exercise alone are not enough, your doctor may recommend medication. Diabetes medications work in different ways: some help your pancreas release more insulin, some help your body use insulin better, and some slow digestion so blood sugar does not spike as fast after eating.
Lowering A1c takes time. It usually takes two to three months of consistent effort to see a meaningful drop in your next A1c test. Your doctor can help you set realistic goals and adjust your plan if something is not working.
A1c versus home blood sugar testing
If you have diabetes, you may also check your blood sugar at home using a glucose meter or continuous glucose monitor. Home testing shows your blood sugar right now; the A1c shows your average over months. Both are useful. Home testing helps you see how specific foods, stress, or activity affect your blood sugar day to day. The A1c tells you and your doctor whether your overall management is working.
Some people with diabetes check their blood sugar several times a day; others check less often. Your doctor will tell you how often you need to test at home based on your type of diabetes and your treatment plan. The A1c test does not replace home testing — they work together to give you and your doctor a complete picture.
Frequently Asked Questions
Can I have a normal A1c and still have diabetes?
Rarely. An A1c of 6.5% or higher is the standard way to diagnose diabetes. If your A1c is below 6.5% but you have symptoms of diabetes (thirst, frequent urination, fatigue), your doctor may order a fasting glucose test or glucose tolerance test instead. Certain blood disorders can also make A1c unreliable, so your doctor may use other tests to confirm.
How often should I get an A1c test?
If you do not have diabetes, your doctor may recommend screening every three years if you are over 45, or more often if you have risk factors. If you have diabetes, most doctors order an A1c test one to two times per year. If you recently started a new medication or made big changes to your diet or exercise, your doctor may test more often to see how you are responding.
What if my A1c is 6.5% — do I definitely have diabetes?
An A1c of 6.5% or higher suggests diabetes, but your doctor will usually order a second A1c test or a fasting glucose test to confirm before making a diagnosis. This is because a single high result can sometimes be due to other factors. Once diabetes is confirmed, your doctor will discuss treatment options with you.
Does stress affect my A1c?
Stress can raise blood sugar in the short term, but the A1c reflects your average over two to three months. Chronic stress may contribute to higher A1c over time, especially if stress leads to poor eating habits or less exercise. Managing stress through activity, sleep, and relaxation can help keep blood sugar more stable.
Can I lower my A1c without medication?
Many people lower their A1c through diet and exercise alone, especially in the early stages of prediabetes or diabetes. However, some people need medication to reach their target. Your doctor can help you figure out what combination of lifestyle changes and medication will work best for you. Even if you take medication, diet and exercise still matter.