An A1C of 6.3% falls in the prediabetes range, which spans 5.7% to 6.4%. It’s not diabetes (that threshold is 6.5% or above), but it’s not normal either, and at 6.3% you’re near the top of the prediabetes range. The good news: this is a point where lifestyle changes can make a real difference. The concerning part: without action, the risk of progressing to type 2 diabetes is significant.
Where 6.3% Falls on the A1C Scale
The A1C test measures your average blood sugar over the past two to three months. The CDC uses three ranges to classify results:
- Normal: below 5.7%
- Prediabetes: 5.7% to 6.4%
- Diabetes: 6.5% or above
At 6.3%, you’re only 0.2 percentage points from a diabetes diagnosis. That narrow margin matters. A systematic review in Diabetes Care found that people with an A1C between 6.0% and 6.5% have a 25 to 50% chance of developing type 2 diabetes within five years. That’s roughly 20 times the risk of someone with an A1C below 5.0%.
If You Already Have Diabetes, 6.3% Is Excellent
Context changes the meaning of this number entirely. For someone already diagnosed with type 2 diabetes, an A1C of 6.3% is well below the standard target of less than 7%. The American Diabetes Association’s 2025 guidelines note that A1C levels between 6% and 7% don’t require pulling back on treatment, as long as you’re not experiencing frequent low blood sugar episodes. In other words, if you’re managing diabetes and hit 6.3%, your blood sugar control is strong.
Health Risks at This Level
Prediabetes isn’t just a warning label for future diabetes. It carries its own health consequences. A study published in The Journal of Clinical Endocrinology and Metabolism tracked people with prediabetes (A1C of 5.7% to 6.4%) and found they had a 38% higher risk of heart failure, heart attack, or stroke compared to people with normal blood sugar. They were also more than twice as likely to develop peripheral artery disease, a condition where narrowed blood vessels reduce blood flow to the legs and feet.
Kidney health is also worth watching. The same study found that prediabetes was linked to worsening protein levels in the urine, an early marker of kidney stress. These aren’t distant, theoretical risks. They develop gradually, often without symptoms, which is exactly why catching prediabetes at 6.3% is valuable. You still have time to change the trajectory.
How to Lower Your A1C
The most well-studied approach comes from the Diabetes Prevention Program, a large clinical trial that tested whether lifestyle changes could prevent or delay type 2 diabetes. Participants aimed for two specific goals: losing 7% of their body weight (about 14 pounds for someone weighing 200) and getting 150 minutes of moderate exercise per week, roughly 30 minutes of brisk walking five days a week. The results were striking. The lifestyle intervention reduced the rate of developing diabetes by 58%, outperforming medication, which reduced it by 31%.
Those two targets, modest weight loss and regular walking, are the foundation. You don’t need to overhaul your entire life. Cutting refined carbohydrates, eating more fiber, and replacing sugary drinks with water can lower blood sugar meaningfully over two to three months, which is the window your next A1C test will reflect. Strength training also helps because muscle tissue absorbs glucose more efficiently than fat tissue.
Will You Need Medication?
This is a gray area. Some clinicians consider prescribing metformin for people with A1C levels between 6.0% and 6.4%, particularly if they also have a higher fasting blood sugar (110 to 125 mg/dL), a BMI of 35 or above, or a history of gestational diabetes. However, there’s genuine debate in the medical community about whether medication is the right move at the prediabetes stage or whether it should be reserved for after a diabetes diagnosis. The Diabetes Prevention Program showed lifestyle changes were nearly twice as effective as metformin, so most providers will recommend starting there.
Your A1C Might Not Be Perfectly Accurate
A few conditions can push your A1C reading higher or lower than your actual blood sugar levels would suggest. Iron deficiency anemia is one of the most common culprits, and it tends to make A1C appear falsely elevated. This is especially relevant for women, particularly during pregnancy, when iron deficiency is more common. Other conditions that can skew results include kidney disease, sickle cell trait or other hemoglobin variants, and chronic bleeding conditions. If your A1C of 6.3% doesn’t match what your daily blood sugar readings show, or if you have any of these conditions, your provider may use a different test to confirm the result.
How Often to Retest
At 6.3%, you’ll typically be retested every 6 to 12 months. If you’ve made significant changes to your diet and exercise habits, retesting at the three-month mark can show whether those changes are working, since A1C reflects a roughly 90-day average. Watching the trend over two or three tests is more useful than fixating on a single number. A drop from 6.3% to 5.8% over six months tells you your approach is working. A climb to 6.5% means it’s time to have a more serious conversation about next steps.