HbA1c test: normal range, chart and what your result means

Your blood sugar over the last three months in one number. Here is how to read it, what moves it, and when it's worth a doctor's visit.

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Quick answer

What is a normal HbA1c level?

A normal HbA1c is below 5.7% (39 mmol/mol). 5.7% to 6.4% (39 to 47 mmol/mol) is the prediabetes range, and 6.5% (48 mmol/mol) or higher is in the diabetes range, which a doctor confirms with a second test. HbA1c shows your average blood sugar over about three months, and you don't need to fast for it.

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Health information, not medical advice. Your doctor knows your full picture; ask them about your result.

Range chart

HbA1c normal range chart

For adults who don't already have diabetes, from the American Diabetes Association and the World Health Organization.

ResultHbA1c (%)HbA1c (mmol/mol)What it usually means
NormalBelow 5.7%Below 39Your blood sugar has been in the usual range.
Prediabetes5.7% to 6.4%39 to 47Higher than usual. A good time to act, because it can often come back down.
Diabetes range6.5% or higher48 or higherIn the diabetes range. A doctor confirms it with a repeat or second test.

Labs can print slightly different reference ranges, so check the one on your own report. In the UK, NICE uses 42 to 47 mmol/mol (6.0% to 6.4%) for the high-risk range.

Turn your HbA1c into average blood sugar

Type the number from your report. You'll see the estimated average glucose it stands for, and the range it falls in.

Estimated average glucose
125 mg/dL
7.0 mmol/L
Same result in the other unit
42 mmol/mol
Range
Prediabetes range

A single result isn't a diagnosis. Diabetes is confirmed with a repeat test or a second kind of test.

Common HbA1c targets if you already have diabetes

Targets are set person by person. These are the usual starting points in the ADA Standards of Care; your doctor may set a different one.

WhoCommon target (%)In mmol/mol
Most adults with diabetesBelow 7%Below 53
Healthy older adultsBelow 7.0% to 7.5%Below 53 to 58
Older adults with several other conditionsBelow 8%Below 64
Pregnancy with diabetesBelow 6% where it's safe, otherwise below 7%Below 42, otherwise below 53
Children and teenagers with diabetesBelow 7%Below 53

A target is set lower or higher depending on your risk of low blood sugar, your other conditions and your age.

What does an HbA1c test measure?

HbA1c stands for glycated haemoglobin (you'll also see glycosylated haemoglobin, A1C or HbA1c). Haemoglobin is the protein in red blood cells that carries oxygen. Sugar in your blood sticks to it, and the more sugar there has been, the more of your haemoglobin ends up coated.

Red blood cells live for about three months, so HbA1c reflects your average blood sugar over the past two to three months, with the last month counting most. That's why it's steady: one sweet dinner or one stressful morning barely moves it, and you don't need to fast before the test.

Doctors use it in three ways: to find diabetes and prediabetes, to see how well diabetes treatment is working, and to judge the risk of diabetes complications over time.

How does HbA1c convert to average blood sugar?

Your HbA1c can be turned into an estimated average glucose (eAG), the number a home meter would average if you checked around the clock. The conversion comes from the ADAG study (Nathan and colleagues, Diabetes Care, 2008).

HbA1cmmol/molAverage glucose (mg/dL)Average glucose (mmol/L)
5%31975.4
6%421267.0
7%531548.6
8%6418310.2
9%7521211.8
10%8624013.4
11%9726914.9
12%10829816.5

The estimate is an average. Two people with the same HbA1c can have quite different days: one steady, one swinging between highs and lows. If you use a sugar meter or a sensor, those readings tell the rest of the story.

What does a high HbA1c mean?

5.7% to 6.4% (prediabetes). Your blood sugar has run higher than usual, but not in the diabetes range. It's common, it usually has no symptoms, and it's the best moment to act: in the US Diabetes Prevention Program, people who lost about 7% of their weight and stayed active cut their chance of developing type 2 diabetes by more than half.

6.5% or higher (diabetes range). A single result here isn't a diagnosis on its own. Unless you have clear symptoms of high blood sugar, a doctor repeats the HbA1c or checks a fasting glucose or a glucose tolerance test to confirm it.

Already living with diabetes? A rise above your target usually means the plan needs a look: medicines, food, activity, sleep, stress and other illnesses can all push it up. Bring the number to the doctor who treats your diabetes rather than changing anything on your own.

HbA1c can also read higher than your true average with iron-deficiency anaemia, low vitamin B12 or folate, advanced kidney disease, or after the spleen has been removed.

What does a low HbA1c mean?

For most people without diabetes, a result in the low part of the normal range is simply good news.

It can read lower than your true average when red blood cells are being replaced faster than usual: after heavy blood loss or a transfusion, with some kinds of anaemia, in the second half of pregnancy, with advanced kidney disease treated with erythropoietin, or with some liver disease. Some haemoglobin variants (such as sickle cell trait, or HbE, which is common in South and Southeast Asia) can make some test methods read low or high.

If you take insulin or sugar-lowering tablets and your HbA1c is very low, it can mean frequent low-sugar episodes. That's worth a call to your doctor, especially if you've had shaky, sweaty or confused spells.

When is HbA1c not the right test?

Because HbA1c depends on red blood cells, doctors use glucose tests instead (fasting glucose, a glucose tolerance test or a fructosamine test) when:

  • you're pregnant, especially for gestational diabetes, which is checked with a glucose tolerance test
  • you've recently lost a lot of blood or had a transfusion
  • you have anaemia, a haemoglobin variant, or advanced kidney or liver disease
  • type 1 diabetes may be starting quickly, often in a child or young adult with thirst and weight loss, where waiting three months for HbA1c to catch up isn't safe

Do you need to fast for the test?

  • No fasting is needed. You can eat and drink as usual.
  • It's a small blood sample from a vein in your arm, or a finger-prick test at some clinics.
  • Results usually come back the same day or within one to two days.
  • Tell the lab or your doctor if you're pregnant, have anaemia or kidney disease, or have had a transfusion or heavy bleeding in the last three months.

How often should you check your HbA1c?

These are the usual intervals in the ADA Standards of Care:

  • Normal result, no diabetes: adults are checked from age 35, or earlier if overweight with other risk factors, and every three years if the result stays normal.
  • Prediabetes: once a year.
  • Diabetes, at target: at least twice a year.
  • Diabetes, treatment just changed or not at target: about every three months.

How can you lower a high HbA1c?

HbA1c moves slowly, so give any change two to three months to show.

  • Move more. About 150 minutes a week of brisk walking or similar activity, spread over most days, plus a little strength work.
  • Swap sugary drinks and refined starches (sweetened tea, juice, white bread, large portions of rice) for water, vegetables, pulses and whole grains.
  • Lose a little weight if you carry extra. Losing 5% to 7% of body weight already makes a measurable difference.
  • Sleep and stress count too. Short sleep and long stress both raise blood sugar.
  • Medicines are your doctor's decision. Many people need them, and that's not a failure. Never start, stop or change a diabetes medicine without your doctor.

When to see a doctor

Book a visit

  • Your HbA1c is 6.5% (48 mmol/mol) or higher for the first time: see a general physician or diabetologist within 1 to 2 weeks to confirm it and plan next steps.
  • It's in the prediabetes range (5.7% to 6.4%): see a general physician within the next month to plan how to bring it down.
  • You have diabetes and your HbA1c is above your target, or below 6% while you take insulin or sugar-lowering tablets: tell the doctor who treats your diabetes within 1 to 2 weeks.
  • You're always thirsty, passing urine often, losing weight without trying, or your vision is blurred: see a doctor within a few days, sooner if it's getting worse.

Get emergency help now (call your local emergency number) if someone with high blood sugar has:

  • vomiting that won't stop, deep or fast breathing, or a fruity smell on the breath
  • confusion, extreme drowsiness, or is hard to wake
  • signs of very low sugar that don't get better after taking sugar: shaking, sweating, confusion, fainting or a fit

An HbA1c number on its own is never an emergency. These signs are.

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Questions people ask

  • HbA1c stands for glycated haemoglobin, also called glycosylated haemoglobin or haemoglobin A1c. "Hb" is haemoglobin, the oxygen-carrying protein in red blood cells, and "A1c" is the part of it that sugar sticks to. The test measures how much of your haemoglobin has sugar attached, which shows your average blood sugar over about three months.

  • For adults without diabetes, a normal HbA1c is below 5.7% (39 mmol/mol). 5.7% to 6.4% is the prediabetes range and 6.5% or higher is in the diabetes range. Labs can print slightly different reference ranges, so compare your result with the range on your own report.

  • 5.7% (39 mmol/mol) is the point where the prediabetes range starts, so it's just above normal. It isn't diabetes, and it's often the easiest stage to turn around with more activity, fewer sugary drinks and a little weight loss. Recheck it in about a year, or sooner if your doctor suggests it.

  • 6.5% (48 mmol/mol) is the threshold for the diabetes range. One result at this level is usually confirmed with a repeat HbA1c or a fasting glucose test before a diagnosis is made, unless you also have clear symptoms such as constant thirst and weight loss. See a general physician within one to two weeks.

  • If you don't have diabetes, 7% is in the diabetes range and needs a doctor's visit within one to two weeks to confirm it. If you already have diabetes, 7% is a common target for many adults, so it may be exactly where your doctor wants it. Your own target depends on your age, other conditions and risk of low sugar.

  • An HbA1c of 10% (86 mmol/mol) means your average blood sugar has been about 240 mg/dL (13.4 mmol/L) for the past few months, well above target. It needs a doctor's review within a few days, not months. Get emergency help if there's vomiting, fast breathing, confusion or extreme drowsiness.

  • No. The ranges used to find prediabetes and diabetes are the same for adults of every age. HbA1c rises slightly with age in healthy people, but not enough to change the cut-offs. What does change with age is the target for people who already have diabetes: older adults are often given a slightly higher target, such as below 7.5% or 8%, to avoid low-sugar episodes.

  • No. HbA1c reflects your blood sugar over about three months, so a meal before the test doesn't change it. You can eat and drink normally. If your doctor has ordered a fasting glucose or a lipid test at the same visit, follow the fasting instructions for those.

  • With a normal result and no diabetes, adults are usually checked every three years from age 35. With prediabetes, once a year. With diabetes, at least twice a year when you're at target and about every three months after a change in treatment or when you're above target.

  • Yes, sometimes. It can read falsely high with iron-deficiency anaemia or low vitamin B12, and falsely low after blood loss or a transfusion, in later pregnancy, with some anaemias, advanced kidney disease, or haemoglobin variants such as HbE or sickle cell trait. If the number doesn't match your sugar readings or symptoms, ask your doctor about a glucose test.

  • Fasting blood sugar is a snapshot: your glucose at one moment after 8 or more hours without food. HbA1c is an average over about three months and doesn't need fasting. A fasting glucose of 126 mg/dL (7.0 mmol/L) or higher and an HbA1c of 6.5% or higher are both in the diabetes range; doctors often use both together.

  • HbA1c follows your red blood cells, which last about three months, so most of a change shows up over two to three months. Some drop can appear after four to six weeks. That's why doctors usually recheck it about three months after a change in diet, activity or medicine.

  • Often, yes. Many people bring their HbA1c back into the normal range with regular activity, less sugar and refined starch, better sleep and losing 5% to 7% of their weight if they carry extra. Even when it doesn't fully return to normal, those changes greatly lower the chance of developing type 2 diabetes.

  • It's used carefully. HbA1c naturally runs lower in the second half of pregnancy, so it can miss high sugar. Gestational diabetes is checked with a glucose tolerance test, usually between 24 and 28 weeks. Women who had diabetes before pregnancy often have HbA1c checked too, with a target their care team sets.

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Sources

  1. American Diabetes Association: Understanding A1C
  2. American Diabetes Association: Standards of Care in Diabetes
  3. CDC: A1C test for diabetes and prediabetes
  4. NIDDK (NIH): The A1C test and diabetes
  5. MedlinePlus: Hemoglobin A1C (HbA1c) test
  6. NICE guideline NG28: Type 2 diabetes in adults
  7. Nathan DM et al. Translating the A1C assay into estimated average glucose values. Diabetes Care 2008

Updated . Health information, not medical advice. Your doctor knows your full picture; ask them about your result.