If you have prediabetes, you should get your A1c checked once a year. That’s the straightforward recommendation from the American Diabetes Association, and it applies whether your prediabetes was diagnosed by A1c, fasting glucose, or an oral glucose tolerance test. But depending on your situation, the timing might shift slightly, and understanding why can help you stay on top of your numbers.
Why Once a Year Is the Standard
Prediabetes means your A1c falls between 5.7% and 6.4%. Below 5.7% is normal, and 6.5% or above is diabetes. Within that prediabetic range, the higher your number, the greater your risk of progressing to type 2 diabetes. Annual testing strikes a balance: it’s frequent enough to catch a meaningful shift, but not so frequent that you’re testing before real change has had time to show up.
The biology behind the test explains that timing. A1c measures how much sugar has attached to your red blood cells over their roughly 120-day lifespan. That means any single A1c result reflects your average blood sugar over the previous three months. Testing more often than every three months won’t give you meaningfully new information, because the red blood cells carrying that data haven’t fully turned over yet.
What the Numbers Say About Progression
One reason annual testing feels right is that prediabetes typically moves slowly. A large pooled analysis of 19 studies found that within 10 years, only about 12.5% of people with prediabetes progressed to type 2 diabetes. Meanwhile, 36% reverted to normal blood sugar levels. Progression is more common than that, though, if your fasting glucose is in the higher end of the prediabetic range. In the highest quartile, the 10-year progression rate climbed to 16%, and the chance of reverting dropped to just 13%.
This means that for most people with prediabetes, a yearly check provides plenty of lead time to detect a trend before it crosses into diabetes territory. But if your A1c is closer to 6.4% than to 5.7%, you and your doctor may want to keep a closer eye on things.
When More Frequent Testing Makes Sense
The once-a-year guideline is a baseline, not a ceiling. If you’ve recently made significant changes to your diet, exercise routine, or weight, you might reasonably recheck your A1c after three to six months to see whether those changes are working. Guidelines from a Canadian health technology assessment suggest a minimum retesting interval of about 60 to 86 days, and recommend rechecking at three months when someone hasn’t yet reached a stable target.
If you’ve been prescribed metformin for prediabetes (which some doctors recommend alongside lifestyle changes), that’s another reason your provider might test more frequently at first, then shift back to annual monitoring once your numbers stabilize. The same applies if you’ve had gestational diabetes, polycystic ovary syndrome, or other conditions that raise your risk profile beyond what a single A1c number captures.
If Your Results Come Back Normal
Some people land in the prediabetic range on one test, make lifestyle changes, and see their A1c drop below 5.7% on the next. That’s genuinely good news, but it doesn’t mean you can stop testing entirely. The U.S. Preventive Services Task Force recommends that adults with a normal glucose result get rescreened every three years, since risk factors like age, weight, and family history don’t disappear. If you were once prediabetic, staying on a three-year cycle after reverting to normal is a reasonable approach.
A1c vs. Fasting Glucose for Monitoring
Your doctor might use A1c, a fasting blood glucose test, or both. A1c has practical advantages: you don’t need to fast, and the test can be done at any time of day, which makes it easier to fit into a routine visit. It also captures a broader picture of your blood sugar control rather than a single-moment snapshot.
One thing to be aware of is that these tests don’t always agree. It’s possible to have a normal fasting glucose but an A1c in the prediabetic range, or vice versa. That’s partly because they measure different things: fasting glucose tells you what your blood sugar is doing right now, while A1c averages it over months. Certain conditions can also skew A1c results. Anemia, recent blood loss, or anything that changes how quickly your red blood cells turn over can make A1c readings less reliable. If your results seem inconsistent with how you feel or what other tests show, your provider may use a different method to confirm.
What Medicare and Insurance Cover
If cost is a concern, Medicare Part B covers up to two diabetes screening blood tests per year for people at risk, and these can include A1c tests. Most private insurance plans cover annual A1c screening for prediabetes as a preventive service. If you need more frequent testing because of a medication change or a new intervention plan, coverage varies, so it’s worth checking with your insurer before scheduling an extra test.
Making the Most of Each Test
Because you’re only testing once or twice a year, each result carries real weight. A few things can help you get an accurate picture. Try to keep your health routine consistent in the weeks before the test, since illness or a course of steroids can temporarily spike blood sugar and distort results. If you know your red blood cell turnover is unusual (from iron deficiency, sickle cell trait, or recent blood donation), mention that to your doctor so they can interpret the number in context.
Between tests, the lifestyle factors that actually move A1c are well established: regular physical activity, modest weight loss (even 5 to 7% of body weight makes a measurable difference), and a diet that limits refined carbohydrates. These are the same interventions that drove the high reversion rates seen in large studies. Annual A1c testing is really just the scoreboard for the work you’re doing the other 364 days of the year.