Diabetes guide
A1C explained: what the numbers mean
Understand screening ranges, treatment targets, and when a repeat test may be needed.
Fight Diabetes For Good editorial desk · Last reviewed:
What the test measures
A1C measures the percentage of hemoglobin in your red blood cells that has glucose attached to it. The result reflects average blood glucose over roughly three months, with recent weeks contributing more. A home meter shows a reading at a specific time. A continuous glucose monitor can show patterns through the day that the average can hide.
How A1C is used for diagnosis
For most nonpregnant adults, the standard laboratory ranges used to screen for and diagnose prediabetes or diabetes are:
| A1C | Standard screening range |
|---|---|
| Below 5.7% | Below the prediabetes range |
| 5.7% to 6.4% | Prediabetes range |
| 6.5% or higher | Diabetes range |
If you have no clear symptoms, an abnormal result generally needs confirmation with another test. Your clinician may repeat the A1C or use another laboratory glucose test. A1C alone does not identify the type of diabetes. Pregnancy, some blood disorders, a recent transfusion, and other conditions that affect red blood cells can make A1C harder to interpret. Tell your clinician if any apply, or if your readings and A1C seem to disagree.
Set a goal with your care team
A treatment goal is a different use of A1C from diagnosis. A goal below 7% is common for many adults with diabetes, but your own target can differ. Ask how your target accounts for your age, other health conditions, and risk of low blood sugar. Write down your target and ask when to check again, especially if you recently started or changed a treatment.
Make the result useful at your next visit
Bring your last two results with dates. If you track glucose at home, bring a meter report or a few representative days from a glucose logbook. Include times when you felt unwell and what was happening that day. Ask whether the next step is another test, reviewing a glucose pattern, or changing part of your care plan with your clinician.
For a result in the prediabetes range, read Prediabetes: what it is and first steps. For questions about a sustained result after type 2 diabetes treatment, see our guide to remission.
Read your result in three steps
- Check why the test was ordered. An A1C for screening answers a different question from a test used to follow diabetes you already have. Look at the report alongside the notes from your visit.
- Check the date and units. A1C is often shown as a percentage in the United States. Some reports use mmol/mol. Keep the original report so the clinic can compare like with like.
- Ask for a next step. Write down whether the result needs confirmation, how it compares with your personal goal, and when the next test is due.
Suppose a screening result comes back at 6.1%. That is in the prediabetes range. Ask whether the result needs another test and what kind of follow-up your clinician recommends. If you already have diabetes, a result in the same range may mean something different. It could reflect your recent treatment, so keep following your plan and discuss it at your next visit.
Use home readings to fill in the gaps
A1C averages out highs and lows. Two people can have similar A1C results and very different days. One might stay close to their usual range most of the time, while another has both high and low readings. If you have episodes of low glucose, tell your clinician even when your A1C is within goal.
To prepare for a visit, mark a few days that show the issue you want to talk about. For example, record when a low occurred, whether you had been active, and what medicine or meal came before it. Ask which details are useful for your care team. You can bring a printed report or a log rather than copying every reading by hand.
Ask about a result that seems out of step
A reading during a short illness or after a particular meal may look different from your three-month average. If your A1C and your home readings repeatedly disagree, ask the clinic to review both. Mention anemia, a recent transfusion or blood loss, kidney disease, or a known hemoglobin variant. These details can help the clinician decide whether to use a different test or another way to follow glucose.
If you are pregnant or planning a pregnancy, ask which tests your care team recommends. The usual A1C screening table on this page does not describe how gestational diabetes is diagnosed.
Make a plan for the next test
The ADA recommends checking glycemic status at least twice a year for people meeting their treatment goals and more often, often about every three months, when treatment changes or goals are not being met. Ask your care team what schedule applies to you. Set a reminder for the appointment and note any questions that come up between visits.
If you just got a diagnosis, use our first-appointment checklist to write down what the test means, what to monitor, and who to contact about your plan.
Keep a simple record of results
Use one line for each test. Record the date, result, and the goal your team gave you at the time. If your treatment or health changed before the test, add a brief note. At a visit, ask whether a difference between two results is meaningful for you and what other information would help interpret it.
If your care team gives you an estimated average glucose, ask how it relates to your A1C. It is an estimate over time, so it can look different from a fasting meter reading. Bring the original report when discussing both numbers.
Common questions
Do I need to fast for an A1C test?
Usually no. If other blood tests are scheduled at the same time, check whether any of those require fasting.
What A1C number means prediabetes?
A laboratory A1C of 5.7% to 6.4% is in the prediabetes range for most nonpregnant adults. A clinician can tell you whether it needs confirmation.
Does an A1C of 6.5% mean I have diabetes?
It is in the diabetes range. If you have no clear symptoms, your clinician generally confirms the diagnosis with another laboratory test.
Why is my A1C different from my glucose meter readings?
A1C summarizes glucose over several months, while a meter shows a moment in time. Some health conditions can also affect A1C, so share both sets of information with your clinician.
How often should I get my A1C checked?
Your care team sets the schedule. Many people with diabetes who meet their goals are checked at least twice a year and more often after a treatment change.