What A1C measures and why it matters
A1C is a blood test that shows your average blood sugar level over the past two to three months. It's measured as a percentage. A normal A1C is below 5.7%. When A1C reaches 5.7% to 6.4%, you have prediabetes. At 6.5% or higher, the diagnosis is type 2 diabetes.
The test works because glucose sticks to hemoglobin, a protein in red blood cells. Since red blood cells live about three months, A1C captures the average of your blood sugar during that window. This is different from a finger-stick test at home, which shows only what your blood sugar is at that exact moment. A1C tells a longer story.
Doctors use A1C to diagnose diabetes and to track how well treatment is working. It's one of the most reliable measures available because it doesn't depend on when you last ate or how stressed you were that morning.
Key Takeaways
- A1C below 5.7% is considered normal; between 5.7% and 6.4% indicates prediabetes; 6.5% or higher indicates type 2 diabetes.
- A1C reflects your average blood sugar over two to three months, so a single high reading won't change your A1C much.
- For people with diabetes, target A1C goals usually range from 6.5% to 8%, depending on age, other health conditions, and how long you've had diabetes.
- Lowering A1C by even 1% reduces your risk of heart disease, kidney damage, and eye problems.
- A1C alone doesn't tell the whole story—your doctor will also look at how often your blood sugar swings high and low.
Understanding prediabetes: A1C between 5.7% and 6.4%
Prediabetes means your blood sugar is higher than normal but not yet in the diabetes range. At this stage, your body is starting to have trouble managing glucose, but the damage is not yet permanent. This is the window where lifestyle changes can prevent or delay type 2 diabetes.
Research shows that losing 5% to 10% of your body weight, exercising 150 minutes per week, and eating less processed food can lower A1C by about 0.5% to 1%. For some people, these changes are enough to bring A1C back below 5.7%. Even if you don't reach that goal, slowing the rise in A1C buys time and reduces your risk of complications later.
Your doctor may or may not recommend medication at the prediabetes stage. Metformin is sometimes prescribed, especially if you're over 60, have a family history of diabetes, or have other risk factors like high blood pressure. But the first step is always the same: understanding what you eat, how much you move, and what changes feel realistic for your life.
A1C targets for people with type 2 diabetes
Once A1C reaches 6.5%, the diagnosis is type 2 diabetes. But "diabetes" doesn't mean one target for everyone. Your doctor will set a goal based on your age, how long you've had diabetes, other health conditions you have, and whether you're at high risk for low blood sugar.
For most adults with type 2 diabetes, the target A1C is between 7% and 8%. An A1C of 7% is often called "good control." Reaching it significantly lowers your risk of heart attack, stroke, kidney disease, and vision loss. However, pushing A1C much lower than 7% doesn't always help more—and it can increase the risk of low blood sugar episodes, which carry their own dangers.
Older adults or those with multiple serious health conditions may have a higher target, such as 7.5% to 8%, because the risks of aggressive treatment outweigh the benefits. People with a short life expectancy or advanced complications may have even higher targets. Your doctor should discuss what makes sense for your situation.
How A1C targets change with age
Age changes what doctors recommend because the risks and benefits of tight control shift. Younger people have more years ahead to develop complications, so reaching lower A1C targets (6.5% to 7%) is usually worth the effort. Middle-aged adults typically aim for 7% to 7.5%. Older adults, especially those over 75 or with multiple chronic illnesses, may do better with a target of 7.5% to 8% or even higher.
The reason is that very tight control in older people increases the chance of hypoglycemia—dangerously low blood sugar—which can cause falls, confusion, heart problems, and stroke. For someone in their 80s with heart disease and kidney disease, a slightly higher A1C may be safer than chasing a perfect number.
Your doctor should tell you what your personal target is and why. If you're not sure, ask. Your target may also change over time as your health changes or as you get older.
What happens between A1C tests
A1C is measured every three months for people newly diagnosed or those whose diabetes isn't yet controlled. Once you reach your target and stay there, testing may move to every six months or once a year. This schedule gives your doctor enough information to see trends without unnecessary testing.
Between tests, you can check your own blood sugar at home with a meter or continuous glucose monitor (CGM). These tools show you the day-to-day picture: which foods spike your blood sugar, how exercise affects it, and whether you're having low blood sugar episodes you don't notice. A1C won't catch these patterns, but your home readings will.
Some people have an A1C that looks good on paper but experience wild swings between high and low blood sugar. Others have a steady A1C but spend most of their time above their target. Your doctor may recommend a CGM to see the full picture, especially if your A1C isn't moving in the right direction despite your efforts.
Why A1C alone isn't the whole story
A1C is an average. If your blood sugar is 250 mg/dL half the time and 100 mg/dL the other half, your A1C might be 7%—which looks controlled. But those high readings damage your blood vessels and nerves. A1C doesn't capture that risk.
Your doctor should also look at your fasting blood sugar (the level when you wake up), how much your blood sugar varies day to day, and whether you're having low blood sugar episodes. A continuous glucose monitor provides this detail. So does a simple log of home blood sugar readings taken at different times of day.
Blood pressure and cholesterol matter just as much as A1C for preventing heart disease and stroke. If your A1C is 7% but your blood pressure is 160/100, your risk is still high. Diabetes management means treating the whole picture, not just one number.
How to lower your A1C
The most effective way to lower A1C is to reduce how much glucose enters your bloodstream and how long it stays there. This happens through food choices, physical activity, weight loss, stress management, and sleep—and sometimes medication.
Eating less refined carbohydrate (white bread, sugary drinks, pastries) and more fiber, protein, and healthy fat slows the rise in blood sugar after meals. Exercise, especially after eating, helps your muscles pull glucose from your blood. Losing weight improves how well your body uses insulin. All of these changes lower A1C over weeks to months.
If lifestyle changes alone aren't enough, medication can help. Metformin is usually the first choice because it's been used for decades, is affordable, and has few side effects. Other medications work in different ways: some help your pancreas release more insulin, some help your kidneys remove glucose in urine, and some slow digestion. Your doctor will choose based on your A1C, kidney function, weight, and other health conditions.
Frequently Asked Questions
Can a single high blood sugar reading raise my A1C?
No. A1C reflects an average over two to three months, so one high reading won't change it much. You'd need many high readings over weeks to shift your A1C. This is why A1C is so useful—it smooths out the day-to-day noise and shows the real trend.
What's the difference between A1C and fasting blood sugar?
Fasting blood sugar is measured after you haven't eaten for eight hours and shows only that moment. A1C shows your average over months. Both are useful. Fasting blood sugar tells you how well your body controls glucose overnight and in the morning. A1C tells you the bigger picture of how well your treatment is working overall.
If my A1C is 6.8%, do I have diabetes?
Yes. The threshold for type 2 diabetes is A1C of 6.5% or higher. An A1C of 6.8% meets that definition. However, having the diagnosis doesn't mean you're in immediate danger. Many people with A1C in the 6.5% to 7% range live long, healthy lives with proper treatment and lifestyle management.
How quickly can A1C come down?
A1C typically drops about 0.2% to 0.3% per month with consistent changes to diet and exercise. Medication can speed this up. Because A1C reflects a three-month average, you won't see the full effect of changes for six to eight weeks. This is why doctors retest every three months rather than every week.
Is an A1C of 5.5% better than 7% if I have diabetes?
Not necessarily. For someone with type 2 diabetes, pushing A1C much below 7% increases the risk of low blood sugar without much additional benefit for most people. Your doctor sets a target based on your age and health, not on how low you can go. Chasing a very low A1C can actually be harmful.