Hemoglobin A1C Test Results Explained

Plain-English guide · Last updated October 17, 2026 · Based on NIH and U.S. government sources

The short version: A1C shows your average blood sugar over about the past 3 months. The ranges commonly used are below 5.7% normal, 5.7% to 6.4% prediabetes and 6.5% or higher diabetes. A diagnosis usually needs a second test, and some conditions can make A1C less accurate. Always review your result with your doctor.

What the A1C test measures

Sugar (glucose) in your blood sticks to hemoglobin, the protein in red blood cells that carries oxygen. The A1C test measures what percentage of your hemoglobin is coated with sugar. The higher the percentage, the higher your blood sugar has been on average (MedlinePlus).

Because red blood cells live for a while, A1C reflects your average blood sugar over the past 3 months, according to the NIDDK. That makes it different from a fasting glucose test, which shows a single moment (NIDDK). You usually don't need to fast for it. The A1C test is used to find prediabetes and type 2 diabetes, and to help people who already have diabetes see how their plan is working.

What your A1C number means

MedlinePlus and the NIDDK list the same ranges for diagnosis (MedlinePlus, NIDDK):

Sources: MedlinePlus and NIDDK. Your lab and doctor may use a different target for you.
A1C	What it generally means
Below 5.7%	Normal
5.7% to 6.4%	Prediabetes
6.5% or higher	Diabetes

MedlinePlus stresses that these ranges are a guide. What's healthy for you depends on your health, age and other factors, so ask your provider what A1C is right for you. If a result is high, providers often repeat the A1C or use another test, such as fasting glucose, before making a diagnosis. The NIDDK advises a repeat test on a different day to confirm a result in the diabetes or prediabetes range.

Things that can make A1C less accurate

The NIDDK lists several situations where A1C can be off (NIDDK):

Very low iron, such as iron-deficiency anemia, can cause a falsely high A1C. See our ferritin guide.
Kidney failure, liver disease, recent blood loss or a blood transfusion can change A1C.
Some people carry a hemoglobin variant (more common in people of African, Mediterranean or Southeast Asian descent, or with family members who have sickle cell anemia or thalassemia). This can interfere with some A1C tests, and a different test may be better.

Why A1C matters

Prediabetes means blood sugar is higher than normal but not yet in the diabetes range. According to the NIDDK, healthy living may help prevent or reverse insulin resistance and prediabetes and may help prevent or delay related health problems (NIDDK). Finding a high A1C early gives you and your doctor time to act.

Possible reasons for a higher A1C

These are possible causes, not a diagnosis. The NIDDK lists these risk factors for prediabetes (NIDDK):

Having overweight or obesity, and not being physically active
Older age and a family history of diabetes
Being African American, American Indian, Asian American, Hispanic, Latino or Pacific Islander
Smoking or being exposed to secondhand smoke
A history of gestational diabetes, or other conditions such as polycystic ovary syndrome

A result can also be skewed by the test issues listed above, which is one reason your doctor may repeat it.

Natural-first, plant-based steps to discuss with your doctor

The NIDDK describes healthy living for prediabetes as healthy foods and drinks, being physically active, managing your weight and getting enough sleep, starting with small changes (NIDDK). Plant-based ideas that fit that advice:

Build meals around whole plant foods: beans, lentils, whole grains, vegetables, fruit, nuts and seeds.
Swap sugary drinks for water or unsweetened tea, and choose whole grains over refined ones.
Move more in ways your doctor agrees are safe, such as a walk after meals.
Protect your sleep and don't smoke.
Plan and track small changes; the NIDDK notes this can help.

Many supplements are marketed for blood sugar. NCCIH advises talking with your health care providers before taking any supplement, especially if you take medicines (NCCIH).

Medicines and safety notes

Don't stop or change any medicine on your own. If you take diabetes medicine, talk with your prescriber before changing your diet a lot, because blood sugar can change.
Metformin and vitamin B12: NIH ODS notes that metformin might reduce vitamin B12 absorption and lower blood levels of B12 (NIH Office of Dietary Supplements). If you take metformin, ask your doctor whether to check your B12. See our vitamin B12 guide.

When to talk to your doctor

Your A1C is 5.7% or higher, or your lab flags it.
Your A1C doesn't match your home glucose readings or how you feel.
You have anemia, kidney or liver disease, or a family history of sickle cell trait or thalassemia.
You feel very unwell, confused or faint, or have trouble breathing. Call 911 or seek emergency care.

Questions to ask at your next appointment

What A1C target is right for me?
Do I need a second test, such as fasting glucose, to confirm this?
Could anything, like low iron or a hemoglobin variant, affect my A1C?
Which food and activity changes would help me most?
When should I retest?

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Frequently asked questions

What is a normal A1C?

MedlinePlus and the NIDDK list an A1C below 5.7% as normal, 5.7% to 6.4% as prediabetes, and 6.5% or higher as diabetes. Your doctor may set a different target for you.

Do I need to fast for an A1C test?

Usually not. A1C reflects your average blood sugar over about the past 3 months, so it isn't based on what you ate that morning. Follow your provider's instructions.

Can low iron affect my A1C?

Yes. The NIDDK says very low iron, such as iron-deficiency anemia, can cause a falsely high A1C. Kidney failure, liver disease, recent blood loss, transfusions and some hemoglobin variants can also affect results.

Is prediabetes reversible?

According to the NIDDK, healthy living, including healthy eating, physical activity, weight management and enough sleep, may help prevent or reverse insulin resistance and prediabetes.

I take metformin. Should I think about vitamin B12?

NIH ODS notes that metformin might lower vitamin B12 levels. Ask your doctor whether a B12 test makes sense for you, and don't change your medicine without talking to your prescriber.

Sources

Medical disclaimer: This article is general education, not medical advice. It does not diagnose, treat, cure or prevent any disease. Always talk with your doctor about your lab results, and talk with your prescriber before starting, stopping or changing any medicine or supplement. If you think you have a medical emergency, call 911. Last updated October 17, 2026.