An A1C of 5.7% sits right at the threshold of prediabetes, the zone where your body is starting to handle blood sugar less efficiently but has not yet crossed into type 2 diabetes. The American Diabetes Association defines prediabetes as an A1C between 5.7% and 6.4%, with 6.5% and above indicating diabetes. At 5.7%, you are at the very bottom of that range, which is both a reason to pay attention and a reason for cautious optimism: you have caught the problem early, when it is most responsive to change.
What A1C Actually Measures
Your A1C result reflects how much glucose has been sticking to your red blood cells over the past two to three months. Glucose attaches to hemoglobin, the oxygen-carrying protein inside red blood cells, through a slow chemical process. Because red blood cells live for roughly 120 days, the A1C test captures a rolling average of your blood sugar during that window rather than a single-moment snapshot.1Europe PMC. A1C versus glucose testing: a comparison A fasting glucose test tells you what your blood sugar is right now; the A1C tells you what it has been doing for weeks.
For an A1C of 5.7%, researchers have worked out a formula that converts the percentage into an estimated average glucose. Using a widely cited equation from a large international study, a 5.7% A1C corresponds to an estimated average blood sugar of roughly 117 mg/dL.2PubMed Central. Translating the A1C assay into estimated average glucose values That number is not alarmingly high on any given day, but it suggests your blood sugar is spending more time elevated than it should, especially after meals.
Why 5.7% Is the Line
The 5.7% cutoff was chosen because research showed it marks the point where risk of future diabetes and its complications begins to rise meaningfully. In a large study of people at increased diabetes risk, an A1C between 5.7% and 6.4% identified roughly a quarter of all at-risk individuals, though it was better at flagging risk in some groups than others. Among African Americans, it identified about 31% of those at risk, and among Hispanic participants about 35%, compared with only about 10% of non-Hispanic white participants.3Europe PMC. A1C between 5.7 and 6.4% as a marker for identifying pre-diabetes, insulin sensitivity and secretion, and cardiovascular risk factors: the Insulin Resistance Atherosclerosis Study (IRAS) Those differences are worth knowing about, because they hint at a broader issue: the A1C test does not perform identically across all populations.
The test’s sensitivity for catching prediabetes, using 5.7% as the cutoff, lands around 53% with a specificity near 60% in study populations that include people with pancreatic conditions.4Frontiers in Endocrinology. Optimal glycated hemoglobin A1c value for prediabetes and diabetes in patients with pancreatic diseases In plain terms, the A1C test at 5.7% catches a little more than half the people who actually have prediabetes and correctly rules it out about 60% of the time. It is useful, but far from perfect, and your doctor may want to confirm the result with another type of test.
What Is Happening Inside Your Body
At 5.7%, two things are likely going on. First, the cells in your muscles, liver, and fat tissue are becoming less responsive to insulin, the hormone that tells them to absorb glucose from your blood. This is insulin resistance: your pancreas has to work harder to keep blood sugar in a reasonable range. Second, and perhaps more important, the insulin-producing beta cells in your pancreas are already showing early signs of strain. Research strongly suggests that some degree of beta cell dysfunction is required for blood sugar to start creeping upward at all.5Springer. Early beta cell dysfunction vs insulin hypersecretion as the primary event in the pathogenesis of dysglycaemia
Insulin resistance and beta cell dysfunction feed off each other. When cells resist insulin, blood sugar rises, forcing beta cells to pump out even more insulin. Over time, that overwork can damage the beta cells themselves. By the time someone reaches the upper end of prediabetes, they may have already lost a substantial portion of their beta cell function, with some studies estimating losses of 70–80% in people at the high end of impaired glucose tolerance.6Oxford Academic. Preservation of β-Cell Function: The Key to Diabetes Prevention At 5.7%, that level of damage almost certainly has not occurred yet. That is the advantage of catching things at this number: you are intervening when most of your beta cell capacity is still intact.
How Likely Is It That 5.7% Will Become Diabetes?
Not everyone with prediabetes goes on to develop type 2 diabetes. About one-third of people with prediabetes actually return to normal blood sugar levels over time without medication. Still, the lifetime risk is not trivial. A study tracking progression found that 45-year-olds with prediabetes (as defined by ADA criteria) faced a remaining lifetime risk of developing diabetes of roughly 47–58%, depending on sex.7BMJ Publishing Group Ltd. Lifetime risk to progress from pre-diabetes to type 2 diabetes among women and men: comparison between American Diabetes Association and World Health Organization diagnostic criteria The 10-year risk was considerably lower, around 9–14% for the ADA definition of prediabetes. Those numbers tell you something important: this is not an emergency, but it is a trajectory you want to change.
Your personal risk depends heavily on factors like weight, activity level, family history, and age. A 5.7% A1C in a sedentary person carrying significant extra weight represents a steeper trajectory than the same number in someone who is active and lean. The number alone does not seal your fate. What you do with the information matters enormously.
Health Risks That Start Before Diabetes
One of the most important things to understand about prediabetes is that it is not simply a waiting room for diabetes. The damage associated with higher blood sugar does not begin neatly at the 6.5% line. Research has found that some of the long-term complications traditionally attributed to diabetes, including problems with small blood vessels and large arteries, can already be underway during the prediabetic period.8Elsevier / PMC. Prediabetes and Cardiovascular Disease: Pathophysiology and Interventions for Prevention and Risk Reduction
Cardiovascular risk is the most serious concern. A nationwide analysis of hospitalizations found that people with prediabetes had roughly double the odds of acute coronary syndrome and acute ischemic stroke compared with people who did not have prediabetes, along with higher odds of acute heart failure.9Elsevier. Prediabetes is an incremental risk factor for adverse cardiac events: A nationwide analysis Those associations are partly driven by the constellation of factors that tend to travel with prediabetes, including excess weight, elevated blood pressure, and abnormal cholesterol. But the elevated blood sugar itself contributes too.
Even eye health can be affected. A systematic review and meta-analysis found that using the ADA prediabetes criteria (A1C of 5.7–6.4%) picked up significantly more cases of retinopathy than stricter international criteria that start at 6.0%.10Elsevier. Microvascular complications in prediabetes: a systematic review & meta-analysis The authors suggested that retinal screening should be considered starting at 5.7%. This does not mean everyone at 5.7% has eye damage, but it underlines the point that prediabetes is a metabolic state with real consequences, not just a label.
What You Should Do About It
The evidence on reversing prediabetes through lifestyle changes is among the strongest in preventive medicine. In the landmark Diabetes Prevention Program trial, participants who made moderate changes to diet and activity reduced their risk of developing diabetes by 58% compared with a placebo group. The changes were not extreme: about 150 minutes per week of moderate-intensity activity (like brisk walking) and a modest weight loss target of 5–7% of body weight.
Exercise works on the underlying biology in a direct way. Physical activity makes your muscle cells more sensitive to insulin, meaning they absorb glucose more efficiently without needing your pancreas to crank out extra insulin. Research comparing trained and sedentary individuals has found differences in the specific molecular machinery that governs how well muscle tissue takes up glucose.11PubMed Central. Determinants of increased muscle insulin sensitivity of exercise-trained versus sedentary normal weight and overweight individuals You do not need to become an athlete. Consistent moderate activity, the kind where you can talk but not sing, has a genuine effect on insulin sensitivity.
Dietary changes matter too, but the research consistently shows that the combination of activity and modest calorie reduction outperforms any single dietary approach. Reducing refined carbohydrates and added sugars helps limit post-meal blood sugar spikes, but no single “prediabetes diet” has proven definitively superior to others. The Mediterranean diet, lower-carbohydrate approaches, and even well-planned plant-based diets have all shown benefits. The consistent theme is eating more whole foods and fewer processed ones, rather than following a specific branded plan.
Sleep Matters More Than You Think
Sleep is an underappreciated factor in blood sugar regulation. When you consistently get less sleep than your body needs, insulin resistance increases measurably. Studies comparing people under sleep restriction to those sleeping normally found that cutting sleep led to higher insulin levels, higher blood sugar, and reduced insulin sensitivity, with these changes showing up after just a few nights of short sleep.12PubMed Central. Sleep Debt and Insulin Resistance: What’s Worse, Sleep Deprivation or Sleep Restriction?
The mechanism involves stress hormones. Sleep restriction drives up cortisol and shifts testosterone levels in men, both of which worsen insulin resistance. In one experiment, clamping cortisol and testosterone at normal levels during sleep restriction cut the development of insulin resistance by about half.13Oxford Academic. Clamping Cortisol and Testosterone Mitigates the Development of Insulin Resistance during Sleep Restriction in Men Circadian misalignment, from shift work, irregular sleep schedules, or insufficient light exposure, also reduces glucose tolerance by impairing insulin sensitivity.14Cureus. Does Insufficient Sleep Increase the Risk of Developing Insulin Resistance: A Systematic Review
If you are doing everything right with diet and exercise but still sleeping six hours a night or going to bed at wildly different times, your blood sugar may not improve as much as it should. Prioritizing seven to eight hours of consistent sleep is not just good general advice; it is directly relevant to your A1C.
Should You Be on Medication?
Metformin, the most common diabetes drug, is sometimes discussed as an option for prediabetes. The ADA suggests it be considered for people with prediabetes who have additional risk factors, such as a BMI of 35 or higher, age under 60, a history of gestational diabetes, or an A1C that continues to rise.15American Diabetes Association / PubMed Central. Metformin Use in Prediabetes Among U.S. Adults, 2005-2012 But this is not a universal recommendation, and some endocrinologists push back against it.
A thoughtful counterargument goes like this: about two-thirds of people with prediabetes never develop diabetes anyway, and about one-third return to normal on their own. People at the prediabetes stage are not yet at risk for the microvascular complications of diabetes, so the main purpose of metformin would be to delay or prevent a diagnosis that may never come. For individuals whose A1C is closer to 6.0% or higher, or who have fasting glucose above 110 mg/dL, the case for medication is stronger. But at 5.7%, you are at the low end of the range, and the argument for jumping straight to medication is weak for most people.16PubMed Central. Metformin Should Not Be Used to Treat Prediabetes The stronger play at this level is aggressive lifestyle change with close monitoring.
When Your A1C Might Not Be Telling the Full Story
There are situations where your A1C can read higher or lower than your actual blood sugar average warrants. Iron deficiency anemia is one of the best-studied confounders. When you are iron deficient, your red blood cells live longer than usual and undergo structural changes that accelerate glucose attachment, pushing your A1C reading up even though your blood sugar may be well controlled. One study found significantly elevated A1C values in iron-deficient individuals compared to controls, with the effect more pronounced in women.17PubMed Central. Influence of Iron Deficiency Anemia on Hemoglobin A1C Levels in Diabetic Individuals with Controlled Plasma Glucose Levels The underlying mechanism involves changes in red blood cell turnover and hemoglobin structure that increase the rate of glycation.18PubMed Central. Increased Levels of Glycated Hemoglobin A1c and Iron Deficiency Anemia: A Review
Other conditions that affect red blood cell lifespan, such as sickle cell trait, thalassemia, or recent significant blood loss, can also throw off A1C results. If you have any of these conditions, your doctor may prefer to use fasting glucose or an oral glucose tolerance test to assess your blood sugar status instead.
Race and ethnicity also influence A1C readings in ways that are not fully explained by differences in actual blood sugar. A study within the Diabetes Prevention Program found that A1C levels were higher among racial and ethnic minority groups even after adjusting for factors that affect blood sugar, leading the researchers to conclude that A1C may not be valid for comparing glycemic control across racial and ethnic groups.19PubMed Central. Differences in A1C by Race and Ethnicity Among Patients With Impaired Glucose Tolerance in the Diabetes Prevention Program If you are Black, Hispanic, or of South Asian descent and your A1C comes back at 5.7%, the clinical meaning may differ from what it would be for a white individual with the same number. This is an active area of research and a legitimate reason to discuss the result carefully with your doctor rather than relying on the number alone.
Why Different Tests Can Give Different Answers
If your doctor orders additional testing, do not be surprised if the results seem to contradict each other. A large study of over 7,400 U.S. adults compared three common diagnostic tests: A1C, fasting glucose, and the oral glucose tolerance test. The agreement between them was strikingly low. When the glucose tolerance test diagnosed diabetes, the A1C test agreed only 34% of the time, and fasting glucose agreed only 44% of the time.20PubMed Central. Limited Agreement between Classifications of Diabetes and Prediabetes Resulting from the OGTT, Hemoglobin A1c, and Fasting Glucose Tests in 7412 U.S. Adults The tests are measuring overlapping but different aspects of glucose metabolism, and they do not always land on the same diagnosis.
The oral glucose tolerance test, which measures your blood sugar two hours after drinking a glucose solution, is especially good at catching problems with how your body handles a sugar load. A1C, by contrast, can underestimate blood sugar issues in certain populations. Research in HIV-positive patients, for instance, found that A1C consistently underestimated glycemia and that the oral glucose tolerance test picked up problems that other tests missed.21BioMed Central. Diabetes mellitus in HIV-infected patients: fasting glucose, A1c, or oral glucose tolerance test – which method to choose for the diagnosis? While most people with a 5.7% A1C will not need all three tests, knowing that discrepancies exist helps you have a more informed conversation with your healthcare provider about whether additional testing is warranted.
The Mental Health Connection
Getting a prediabetes diagnosis can provoke anxiety, and that emotional response is worth taking seriously, not just for your peace of mind but because mental health and blood sugar regulation are physiologically linked. A community-based cohort study found that people with prediabetes who also had elevated depressive symptoms had more than ten times the odds of developing diabetes compared with people who had neither prediabetes nor depression. The interaction between prediabetes and depression was synergistic, meaning the combined risk was greater than simply adding the two risks together.22PubMed Central. Prediabetes, depressive and anxiety symptoms, and risk of type 2 diabetes: A community-based cohort study Elevated anxiety symptoms showed a similar pattern, with nearly nine times the odds of progression to diabetes when combined with prediabetes.
The likely mechanisms run in both directions. Depression and anxiety increase cortisol, which worsens insulin resistance. They also make it harder to exercise, cook healthy meals, and sleep well, undermining the exact lifestyle changes that matter most for reversing prediabetes. If you are struggling with your mood after getting this result, addressing that struggle is not a distraction from the blood sugar problem. It is part of solving it.
Continuous Glucose Monitors and the Future of Tracking
You may have seen continuous glucose monitors, the small sensors worn on the arm that stream blood sugar data to a phone app, marketed to people without diabetes. There is growing research interest in using these devices for people with prediabetes, because they reveal the moment-to-moment glucose spikes and dips that a single A1C number hides.23Europe PMC. Continuous Glucose Monitoring for Prediabetes: What Are the Best Metrics? A 5.7% A1C tells you the average, but it cannot tell you whether your blood sugar is spiking to 180 mg/dL after meals and then crashing, or sitting at a mildly elevated 120 mg/dL all day. Those two patterns carry different risks and call for different responses.
Researchers are exploring which CGM metrics matter most in prediabetes, including time spent above certain thresholds and overall glycemic variability. Early work using machine learning to analyze CGM data has shown promise in distinguishing prediabetes from normal glucose regulation, potentially catching the transition earlier than a standard A1C test would.24CrossRef. Enhancing Prediabetes Diagnosis from Continuous Glucose Monitoring Data via Iterative Label Cleaning and Deep Learning of Bridge2AI AI-READI Data For now, CGMs are not standard of care for prediabetes and most insurance plans will not cover them for this purpose. But if you are someone who is motivated by real-time feedback and can afford the out-of-pocket cost, wearing one for a few weeks can be eye-opening. Seeing exactly which meals, activities, and sleep patterns move your blood sugar can turn an abstract number into a practical guide for daily decisions.