An A1C of 5.7% sits right at the boundary between normal and prediabetes. It is the lowest value that qualifies as prediabetes under current diagnostic guidelines, meaning your blood sugar has been running slightly higher than ideal over the past two to three months. It’s not diabetes, but it is a signal worth paying attention to.
What 5.7% Means on the A1C Scale
The A1C test measures the percentage of your red blood cells that have sugar attached to them. Because red blood cells live for roughly three months, the test reflects your average blood sugar over that window rather than a single snapshot.
The standard ranges break down like this:
- Normal: below 5.7%
- Prediabetes: 5.7% to 6.4%
- Diabetes: 6.5% or higher
At 5.7%, you’re at the very bottom edge of the prediabetes range. Your blood sugar is higher than someone in the normal category, but only barely. The gap between 5.7% and 6.5% (the diabetes threshold) is meaningful, and most people at 5.7% have time and opportunity to bring that number back down.
What Your Body Is Doing at This Level
An A1C of 5.7% translates to an estimated average blood sugar of about 117 mg/dL. For comparison, a normal fasting blood sugar is under 100 mg/dL. What’s happening is that your cells are becoming less responsive to insulin, the hormone that moves sugar out of your blood and into your cells for energy. Your pancreas compensates by producing more insulin, and for a while that keeps things mostly in check. But blood sugar after meals stays elevated a little longer than it should, and that’s what nudges the A1C upward.
This stage can last years before progressing to diabetes, and in many cases it doesn’t progress at all. About 70% of people with prediabetes do eventually develop type 2 diabetes over their lifetime, but that timeline and outcome depend heavily on what happens next.
Could the Result Be Inaccurate?
Before assuming your blood sugar is truly elevated, it’s worth knowing that certain conditions can push A1C readings higher than your actual blood sugar warrants. Iron deficiency anemia is the most common culprit. When you’re low on iron, a chemical byproduct in your blood accelerates the attachment of sugar to red blood cells, inflating the A1C number even though your blood sugar itself may be normal. This is especially relevant for women in late pregnancy, where iron deficiency commonly develops and can raise A1C readings in people who don’t have diabetes at all.
Kidney disease, certain hemoglobin variants, and very high triglyceride levels can also skew results in either direction. If you have any of these conditions, your doctor may confirm with a fasting blood sugar test or an oral glucose tolerance test instead of relying on A1C alone.
Does Age Change the Interpretation?
Some older research from the 1970s and 1980s found that A1C tends to creep upward with age, even in people without diabetes. This raised the question of whether a 5.7% in a 70-year-old means the same thing as a 5.7% in a 35-year-old. Current evidence hasn’t clearly established that age changes the relationship between A1C and average blood sugar, so the same diagnostic cutoffs apply regardless of age.
What does change with age is how aggressively doctors recommend treating the number. For younger adults, catching prediabetes early offers decades of benefit from prevention. For older adults, particularly those who are frail or have a short life expectancy, the focus shifts more toward avoiding the risks of aggressive blood sugar lowering (like dangerous drops in blood sugar) rather than chasing a specific A1C target.
What Actually Lowers A1C From 5.7%
The good news about catching prediabetes at 5.7% is that lifestyle changes are genuinely effective at this stage, often more so than medication. The landmark Diabetes Prevention Program trial found that people who lost 5% to 7% of their body weight and exercised 150 minutes per week reduced their risk of developing diabetes by 58%. For someone weighing 200 pounds, that’s a loss of 10 to 14 pounds.
The exercise doesn’t need to be intense. Brisk walking counts. The key is consistency: 30 minutes a day, five days a week, or a similar total spread across the week however it fits your schedule. Resistance training (using weights, bands, or body weight exercises) also improves how your cells respond to insulin, and combining it with aerobic activity works better than either alone.
Dietary changes that make the biggest difference at this stage are reducing refined carbohydrates (white bread, sugary drinks, pastries) and replacing them with fiber-rich foods like vegetables, legumes, and whole grains. Fiber slows the absorption of sugar after meals, which directly blunts the post-meal blood sugar spikes that drive A1C up. You don’t need a special diet. Eating fewer processed carbs and more whole foods is the core of it.
How Quickly Can It Change?
Because A1C reflects a three-month average, changes in your habits won’t show up overnight. Most doctors recheck A1C after three to six months. People who make sustained changes typically see their A1C drop by 0.1% to 0.3% over that period, which at 5.7% could bring you back into the normal range.
If your A1C stays at 5.7% or climbs despite lifestyle changes, that’s useful information too. It may point to other factors like genetics, an underlying condition affecting the test, or the need for a more targeted approach. Some people at the higher end of the prediabetes range (closer to 6.4%) are prescribed metformin, but at 5.7%, lifestyle modifications are the standard first step.
What to Watch Going Forward
Once you’ve had an A1C of 5.7%, annual testing is a good idea even if you bring the number down. Prediabetes tends to be a recurring pattern rather than a one-time event, especially if the underlying insulin resistance hasn’t fully resolved. Tracking your A1C over time gives you a clear trend line, which is more useful than any single reading. A stable 5.5% over several years tells a very different story than a 5.5% that used to be 5.3% and keeps climbing.