A normal A1C level is below 5.7%. This number represents the percentage of your red blood cells that have sugar attached to them, and it gives a picture of your average blood sugar over the past two to three months. A result between 5.7% and 6.4% falls into the prediabetes range, and 6.5% or higher on two separate tests indicates diabetes.
What the A1C Test Actually Measures
Sugar in your bloodstream naturally sticks to hemoglobin, the protein inside red blood cells that carries oxygen. Once sugar attaches, it stays for the life of that red blood cell, which is roughly 120 days. The A1C test measures what percentage of your hemoglobin has sugar bonded to it. A higher percentage means your blood sugar has been running higher over the past two to three months.
This is different from a finger-stick glucose test, which only captures your blood sugar at a single moment. You could have a normal reading right after a workout but high blood sugar the rest of the day. The A1C smooths all of that out into one number, which is why it’s considered a more reliable marker for long-term blood sugar control.
A1C Ranges at a Glance
- Normal: Below 5.7%
- Prediabetes: 5.7% to 6.4%
- Diabetes: 6.5% or higher (confirmed with a second test)
A diagnosis of diabetes requires two separate A1C tests at 6.5% or above, not just one. If your result lands in the prediabetes range, it means your blood sugar is elevated but not yet high enough for a diabetes diagnosis. Prediabetes is reversible with lifestyle changes, and catching it at this stage is the whole point of routine testing.
How A1C Translates to Daily Blood Sugar
The percentage on your A1C report can feel abstract. A useful way to think about it: each A1C percentage point corresponds to a specific estimated average glucose (eAG) in milligrams per deciliter, the same unit your home glucose meter uses. The conversion formula is (28.7 × A1C) − 46.7 = eAG.
Here’s what that looks like in practice:
- A1C of 5.0%: Average blood sugar around 97 mg/dL
- A1C of 5.7%: Average blood sugar around 117 mg/dL
- A1C of 6.0%: Average blood sugar around 126 mg/dL
- A1C of 6.5%: Average blood sugar around 140 mg/dL
- A1C of 7.0%: Average blood sugar around 154 mg/dL
So a normal A1C of 5.0% means your blood sugar has been averaging under 100 mg/dL, which is well within a healthy range. Once you cross into prediabetes territory at 5.7%, your average daily glucose is sitting around 117 mg/dL, high enough to signal that your body is starting to struggle with processing sugar efficiently.
No Fasting Required
Unlike a fasting glucose test, the A1C test does not require you to skip meals beforehand. You can eat and drink normally before the blood draw. This makes it one of the more convenient diabetes screening tools, since it can be done at any time of day regardless of when you last ate.
When the A1C Can Be Misleading
Because the test depends on hemoglobin in your red blood cells, anything that changes those cells can throw off the result. The CDC lists several conditions that can falsely raise or lower your A1C:
- Blood disorders like sickle cell anemia or thalassemia alter hemoglobin structure, which can make results unreliable in either direction.
- Severe anemia reduces the number of red blood cells, which can artificially lower your A1C even if blood sugar is actually elevated.
- Kidney failure and liver disease can both distort results.
- Recent blood loss or transfusions change the age and composition of your red blood cells, skewing the reading.
- Pregnancy, particularly early or late stages, affects red blood cell turnover and can produce inaccurate numbers.
- Certain medications, including opioids and some HIV drugs, may interfere with the test.
If any of these apply to you, your doctor may rely on alternative tests like fructosamine or a continuous glucose monitor to get a more accurate picture. The A1C is a strong screening tool for most people, but it has blind spots in specific populations.
What a Prediabetes Result Means
Getting a result between 5.7% and 6.4% doesn’t mean diabetes is inevitable. It means your blood sugar management is slipping and your risk is elevated. Large-scale research has consistently shown that moderate weight loss (around 5% to 7% of body weight) and regular physical activity can cut the risk of progressing to type 2 diabetes significantly.
The changes that move the needle are straightforward: more movement, fewer refined carbohydrates, and smaller portions. Even without weight loss, increased physical activity on its own improves how well your cells respond to insulin. A follow-up A1C test in three to six months can show whether those changes are working, since the test reflects your average over the most recent two to three months.
How Often to Get Tested
For adults with no risk factors, A1C screening typically starts at age 35 or 45, depending on the guidelines your provider follows. If you have risk factors like obesity, a family history of diabetes, or a history of gestational diabetes, earlier and more frequent testing makes sense. People already diagnosed with diabetes generally get an A1C test every three to six months to track how well their management plan is working.
If your result comes back normal, retesting every three years is a common recommendation for people without additional risk. For those in the prediabetes range, annual testing helps catch any upward trend before it crosses the diabetes threshold.