Blood Sugar Levels & HbA1c Chart: Normal, Prediabetes, Diabetes
HbA1c (called A1C in the US) shows your average blood sugar over about the past 3 months. US guidance (ADA 2026) calls below 5.7% normal, 5.7–6.4% prediabetes and 6.5% or more the diabetes range. UK guidance (NICE) works in mmol/mol: 42–47 mmol/mol means a high risk of type 2 diabetes, and 48 mmol/mol or more is the diabetes range. A normal fasting glucose is below 100 mg/dL (5.6 mmol/L). One result in the diabetes range is usually confirmed with a second test.
Units: 6.5% = 48 mmol/mol. Glucose in mg/dL × 0.0555 = mmol/L. The US prediabetes line (5.7%, about 39 mmol/mol) sits lower than the UK’s (42 mmol/mol, about 6.0%). See why.
- Below prediabetes
- Prediabetes range
- Diabetes range
- Already have diabetes
- % to mmol/mol
- UK vs US cut-offs
- Fasting glucose
- Pregnancy
Where does my HbA1c sit?
Type the number from your report, pick its unit and choose US or UK cut-offs. You can add a fasting glucose too. Everything is worked out on your device, and nothing is saved or sent anywhere.
Result in a different unit? Our blood test unit converter switches glucose between mg/dL and mmol/L and HbA1c between % and mmol/mol.
HbA1c levels chart
Top numbers are %, bottom numbers the same points in mmol/mol. The rows show where US and UK guidelines, and two labs, draw their lines.
Sources: ADA Standards of Care 2026 and 2025; NICE PH38 and NG28; Labcorp test 001453; UHNM pathology. Full references below.
| Test | Below prediabetes | Prediabetes range | Diabetes range |
|---|---|---|---|
| HbA1c, US (ADA) | Below 5.7% (39 mmol/mol) | 5.7–6.4% (39–47 mmol/mol) | 6.5% (48 mmol/mol) or more |
| HbA1c, UK (NICE) | Below 42 mmol/mol (6.0%) | 42–47 mmol/mol (6.0–6.4%) | 48 mmol/mol (6.5%) or more |
| Fasting glucose, US (ADA) | Below 100 mg/dL (5.6 mmol/L) | 100–125 mg/dL (5.6–6.9 mmol/L) | 126 mg/dL (7.0 mmol/L) or more |
| Fasting glucose, UK (NICE, WHO) | Below 5.5 mmol/L (99 mg/dL) | 5.5–6.9 mmol/L (NICE); WHO: 6.1–6.9 | 7.0 mmol/L (126 mg/dL) or more |
| 2-hour glucose tolerance test (both) | Below 140 mg/dL (7.8 mmol/L) | 140–199 mg/dL (7.8–11.0 mmol/L) | 200 mg/dL (11.1 mmol/L) or more |
| Random glucose (both) | No cut-off | No cut-off | 200 mg/dL (11.1 mmol/L) or more, with symptoms |
NICE calls the middle band high risk or non-diabetic hyperglycaemia. Without clear symptoms, a diabetes-range result is confirmed with a second test (ADA; NICE PH38).
A1C chart: HbA1c % to mmol/mol and average glucose
US labs report HbA1c in % (NGSP scale), UK labs in mmol/mol (IFCC scale). The NGSP/IFCC master equation links them:
% = (0.09148 × mmol/mol) + 2.152, so mmol/mol = (% − 2.152) ÷ 0.09148.
Estimated average glucose (eAG) comes from the ADAG study: eAG in mg/dL = 28.7 × HbA1c(%) − 46.7 (Nathan 2008). It’s an estimate. For other tests, try our blood test unit converter.
| HbA1c % | mmol/mol | eAG mg/dL | eAG mmol/L | Where it sits |
|---|---|---|---|---|
| 5.0 | 31 | 97 | 5.4 | Normal |
| 5.7 | 39 | 117 | 6.5 | US prediabetes starts |
| 6.0 | 42 | 126 | 7.0 | UK high-risk range starts |
| 6.5 | 48 | 140 | 7.8 | Diabetes range (US and UK) |
| 7.0 | 53 | 154 | 8.6 | Common target in diabetes |
| 7.5 | 58 | 169 | 9.4 | NICE: step up treatment at 58 or more |
| 8.0 | 64 | 183 | 10.2 | Above most targets |
| 9.0 | 75 | 212 | 11.8 | Above most targets |
| 10.0 | 86 | 240 | 13.3 | ADA: very high above this |
| 12.0 | 108 | 298 | 16.6 | Very high |
Values rounded and matching NGSP’s table. Rows 5.7, 6.5 and 7.5 are worked out the same way.
What HbA1c actually tells you
A fasting glucose is a single snapshot from the scene. HbA1c is the security footage from the last few months.
Glucose sticks to hemoglobin (haemoglobin in UK spelling), the oxygen-carrying protein in red blood cells. HbA1c measures how much has been coated, so it reflects your average blood sugar over about the past 3 months (NIDDK). You don’t need to fast for it (NIDDK; NICE PH38).
Blind spots: it misses daily highs, lows and hypos (ADA), and anything that changes red cell lifespan can skew it. It moves slowly, so one NHS lab won’t usually repeat it within 55 days (UHNM).
Fasting glucose, the glucose tolerance test and random glucose
- Fasting plasma glucose: taken after at least 8 hours without food or calorie-containing drinks (ADA).
- Oral glucose tolerance test (OGTT): a 75 g glucose drink, then a blood sample 2 hours later. The UK uses it to test for gestational diabetes (NICE).
- Random glucose: taken at any time. It diagnoses diabetes only at 200 mg/dL (11.1 mmol/L) or more with classic symptoms: thirst, passing a lot of urine or unexplained weight loss (ADA).
Who should be tested
US (ADA): everyone aged 35 and over, and adults of any age with a BMI of 25 or more (23 or more with Asian ancestry) plus a risk factor, such as a close relative with diabetes or high blood pressure. Retest at least every 3 years if normal and yearly with prediabetes.
UK (NICE PH38): a risk assessment from age 40, or from 25 for people of South Asian, Chinese, African-Caribbean or Black African background. In England, the NHS Health Check (ages 40 to 74) includes blood pressure and cholesterol tests and possibly a blood sugar test. High risk means a blood test at least once a year.
What your HbA1c number means
Each band is a case file: clues, usual suspects, the next lead and questions to ask.
Below 5.7% (US) or below 42 mmol/mol (UK)
Your average blood sugar has been in the usual range. One gray zone: 39–41 mmol/mol (5.7–5.9%) is prediabetes in the US only (why).
- Blood loss, hemolysis (red cells breaking down) or a transfusion can make it read falsely low (NGSP)
- Fast-onset diabetes may not show yet
- WHO: below 6.5% doesn’t rule out diabetes found on glucose tests
Tell your doctor, as a glucose test may help. Other suspects: low iron stores, anemia, thyroid, sleep and mood. See our “Always tired?” case file.
Ask: When should I be tested again? Could anything be making my HbA1c read low?
5.7–6.4% (US) or 42–47 mmol/mol (UK)
Higher than usual, but below the diabetes range. NICE calls it high risk, or non-diabetic hyperglycaemia. It’s a chance to act early.
- Usually no symptoms
- Often found on a routine check
- Insulin resistance
- Extra weight, inactivity, family history, past gestational diabetes
- Steroids or some antipsychotics
- A falsely high reading from iron deficiency (NGSP)
A repeat HbA1c or fasting glucose, and a check that low iron isn’t nudging the number up.
ADA and NICE: retest at least once a year. In England, many people can be referred to the Healthier You NHS Diabetes Prevention Programme, a 9-month lifestyle programme.
Ask: Am I eligible for a prevention programme? When should we recheck?
6.5% (48 mmol/mol) or higher
The level US and UK guidelines use to diagnose diabetes. Without clear symptoms, a second test confirms it (ADA; NICE PH38). ADA treats above 10% (86 mmol/mol) as very high and a reason to review treatment promptly.
- Sometimes none at all
- Thirst, passing a lot of urine, tiredness, blurred vision or weight loss (NHS)
- Type 2 diabetes, about 9 in 10 cases (NHS England)
- Type 1, especially with fast onset, weight loss or ketones
- Steroids, or after pancreatitis
A second test, such as a repeat HbA1c or a fasting glucose. If HbA1c may be unreliable for you, glucose tests are used instead (NHS labs).
ADA: a different test the same day, or the same test another day. NICE: a second blood test. Clear symptoms with a very high glucose can be enough alone.
Ask: Which confirmation test do I need? Could anything be distorting my HbA1c? What happens if it’s confirmed?
If you already have diabetes: compare with your own target
HbA1c becomes a progress check. Your diabetes team agrees a target with you, based on your treatment, hypo risk and wider health.
- ADA: below 7% (53 mmol/mol) for many non-pregnant adults, without significant hypos
- NICE: 48 mmol/mol (6.5%) on diet or a medicine that doesn’t cause hypos; 53 mmol/mol (7.0%) on one that can
- Both allow higher targets for some people, such as below 8% (64 mmol/mol) with limited life expectancy (ADA)
NICE: HbA1c every 3 to 6 months until stable, then every 6 months. If HbA1c is unreliable, glucose profiles or fructosamine can be used (NG28).
Ask: What’s my target, and why? Is my number moving the right way? Would a glucose sensor help?
HbA1c and fasting glucose together: the patterns
The two tests measure different things, so they don’t always agree.
| HbA1c | Fasting glucose | Usual pattern |
|---|---|---|
| Below prediabetes | Below prediabetes | No sign of raised blood sugar on these tests |
| Prediabetes | Normal, or the reverse | Common. One test catches what the other misses. Retest within a year. |
| Diabetes range | Diabetes range | Under ADA guidance, this confirms diabetes if both are from the same day. UK practice usually confirms with a second blood test. |
| Diabetes range | Not in the diabetes range (or the reverse) | The results disagree. A repeat is usual, and a big mismatch prompts a look for anything distorting either test (ADA). |
| Higher than glucose suggests | Repeatedly normal | Think of iron deficiency (NGSP) |
| Lower than glucose suggests | Repeatedly high | Think of blood loss, hemolysis, a transfusion or dialysis (NGSP) |
What can throw off an HbA1c result
Before trusting the footage, check nobody tampered with the camera:
- Iron deficiency. Iron deficiency anemia is linked to a falsely high HbA1c. NGSP suggests other measures until it’s treated. See low ferritin and hemoglobin levels.
- Shorter red cell life. Recovery from blood loss, hemolytic anemia or a recent transfusion can make HbA1c read falsely low (NGSP; ADA).
- Hemoglobin variants. Sickle cell trait, HbC and high fetal hemoglobin can interfere, depending on the method (NGSP; Labcorp). They’re more common with African, Mediterranean or Southeast Asian ancestry (NIDDK). ADA says A1C can’t be used in sickle cell disease.
- Kidney disease. On dialysis, HbA1c tends to read low, especially with erythropoietin (NGSP; NHS labs). See kidney function tests.
- Pregnancy. HbA1c runs lower (NHS labs). See pregnancy.
- Fast-rising sugar. HbA1c can lag weeks behind, as in type 1 diabetes or after starting steroids (NHS labs).
- Other factors. WHO lists heavy alcohol use, chronic liver disease, large doses of aspirin, vitamins C and E, and chronic opiate use.
- A unit mix-up. 6.5% and 6.5 mmol/L are very different. Check the unit.
For fasting glucose, the usual planted clue is eating within 8 hours of the test.
Is prediabetes the same in the US and UK?
Prediabetes has no single definition. Guidelines draw the line in different places:
- US (ADA 2026): HbA1c from 5.7% (39 mmol/mol), or fasting glucose from 100 mg/dL (5.6 mmol/L).
- UK (NICE PH38): HbA1c from 42 mmol/mol (6.0%), or fasting glucose from 5.5 mmol/L (99 mg/dL).
- WHO: impaired fasting glucose from 6.1 mmol/L (110 mg/dL). In 2011, WHO found too little evidence for any HbA1c cut-off below 6.5%.
So an HbA1c of 40 mmol/mol (5.8%) is prediabetes on a US report and below the high-risk range on a UK one. Neither lab is wrong. For fasting glucose it’s reversed: NICE’s line (5.5 mmol/L) sits just below ADA’s (5.6). The diabetes cut-off, 6.5% (48 mmol/mol), is the same in both. Go by the guideline your doctor follows.
Pregnancy and children
Pregnancy
HbA1c runs lower in pregnancy, and UK practice doesn’t use it to diagnose diabetes in pregnancy (NHS labs). NICE offers people with risk factors a 75 g glucose tolerance test at 24–28 weeks. In the UK, gestational diabetes means a fasting glucose of 5.6 mmol/L or more, or a 2-hour glucose of 7.8 mmol/L or more (NICE NG3). US cut-offs differ, so your obstetric team will explain theirs.
Children and teenagers
UK labs don’t use HbA1c to diagnose diabetes in children, because most have type 1, which can come on fast (NHS labs). If your child is peeing more, very thirsty, very tired or losing weight, the NHS advises an urgent GP appointment or NHS 111.
Reading HbA1c and glucose on your lab report or app
- Names: HbA1c, A1C, hemoglobin A1c, glycated hemoglobin or GHb. Glucose may appear as fasting plasma glucose or FPG.
- Units: HbA1c in % (US) or mmol/mol (UK); glucose in mg/dL (US) or mmol/L (UK). Some labs add an eAG (NIDDK). Convert with our unit converter.
- Flags: a US report using 4.8–5.6% (Labcorp) flags 5.7% as high. A UK report may print 20–41 mmol/mol with a comment for 42–47 (UHNM). A flag only means outside that lab’s range.
- Apps and portals: US portals often show results before your clinician comments. The NHS App may add a note from your GP practice.
When to get help urgently
- Signs of high blood sugar with being sick, stomach pain, fast breathing or heartbeat, drowsiness, confusion or fruity-smelling breath: call 999 or go to A&E (UK), or call 911 (US) (NHS).
- If you have diabetes and your blood ketones are over 3 mmol/L: call 999 or go to A&E (NHS). Don’t drive yourself.
- Someone with low blood sugar (usually below 4 mmol/L in the UK, or 70 mg/dL in the US) who is unconscious, having a fit or not responding normally: call 999 or 911 (NHS).
- Peeing more, very thirsty and tired, and getting worse quickly, being sick, sleepy or confused, or breathing fast and deep: call 999 or 911 (NHS). If you only suspect type 1 diabetes, get an urgent GP appointment or NHS 111, or call your US doctor the same day.
Blood sugar and HbA1c questions people ask
What is a normal HbA1c level?
Below 5.7% (39 mmol/mol) by US (ADA) cut-offs, or below 42 mmol/mol (6.0%) by UK (NICE) cut-offs. Labcorp prints 4.8–5.6%; NHS labs often print 20–41 mmol/mol.
What is the prediabetes range for HbA1c?
In the US, 5.7–6.4% (39–47 mmol/mol). In the UK, 42–47 mmol/mol (6.0–6.4%), which NICE calls high risk or non-diabetic hyperglycaemia. Both treat 6.5% (48 mmol/mol) or more as the diabetes range.
How do I convert HbA1c from mmol/mol to %?
Multiply mmol/mol by 0.09148 and add 2.152. So 48 mmol/mol is 6.5%. To go back, subtract 2.152 from the % and divide by 0.09148.
What is a normal blood sugar level?
Fasting, below 100 mg/dL (5.6 mmol/L) by ADA cut-offs, or below NICE’s high-risk line of 5.5 mmol/L. Two hours after a glucose drink, below 140 mg/dL (7.8 mmol/L). Below 70 mg/dL (3.9 mmol/L) counts as low in diabetes (ADA); the NHS uses 4 mmol/L.
Is an HbA1c of 6.0% (42 mmol/mol) prediabetes?
Yes, under both US and UK cut-offs. Results of 5.7–5.9% (39–41 mmol/mol) are prediabetes in the US only.
Do I need to fast for an HbA1c test?
No. HbA1c can be done at any time of day. A fasting glucose needs at least 8 hours without food.
Can anemia affect HbA1c?
Yes. Iron deficiency anemia can make HbA1c read falsely high. Blood loss, hemolysis and a recent transfusion can make it read falsely low.
What HbA1c is too high?
6.5% (48 mmol/mol) or more is the diabetes range. ADA treats above 10% (86 mmol/mol) as very high. With vomiting, drowsiness or fast breathing, get urgent help.
How we wrote this page
Written and medically reviewed by Dr. Mustafa Sakr, MBBCh. Last reviewed: October 2026. The numbers come from current guidelines (ADA 2026, NICE, WHO), NGSP and published lab ranges, listed below. We update this page when guidance changes.
How the checker works: it compares your HbA1c, in the unit you enter, with US cut-offs of 5.7% and 6.5% (39 and 48 mmol/mol) or UK cut-offs of 42 and 48 mmol/mol, converting with the NGSP/IFCC master equation. Fasting glucose is compared with 100 and 126 mg/dL (US) or 5.5 and 7.0 mmol/L (UK). Your lab’s range, if entered, sets the top of normal. Values that look like the wrong unit get a hint. Ticking that you have diabetes shows your result beside common targets, without a label. Nothing is stored or sent, and it can’t weigh your symptoms, medicines or history.
References
- American Diabetes Association Professional Practice Committee. 2. Diagnosis and Classification of Diabetes: Standards of Care in Diabetes—2026. Diabetes Care 2026;49(Suppl 1):S27–S49. doi:10.2337/dc26-S002
- American Diabetes Association. Standards of Care in Diabetes—2025 Abridged for Primary Care. Clin Diabetes 2025;43(2); and Diagnosis. Abridged (PDF) · diabetes.org
- NICE. Type 2 diabetes: prevention in people at high risk (PH38), 2012, updated 2017. nice.org.uk (PDF)
- NICE. Type 2 diabetes in adults: management (NG28), 2015, updated February 2026. nice.org.uk (PDF)
- World Health Organization. Use of Glycated Haemoglobin (HbA1c) in the Diagnosis of Diabetes Mellitus, 2011; and Definition and diagnosis of diabetes mellitus and intermediate hyperglycaemia, 2006. WHO 2011 (NCBI Bookshelf) · WHO 2006
- NGSP. Harmonizing HbA1c (IFCC master equation); Convert between IFCC, NGSP and eAG; Factors that interfere with HbA1c test results (updated June 2026). Master equation · Conversion table · Interferences
- Nathan DM, et al. Translating the A1C assay into estimated average glucose values. Diabetes Care 2008;31(8):1473–1478. doi:10.2337/dc08-0545
- NIDDK (NIH). The A1C Test and Diabetes. niddk.nih.gov
- NHS. High blood sugar (hyperglycaemia), 2026; Low blood sugar (hypoglycaemia); Diabetic ketoacidosis; Type 1 diabetes: symptoms; NHS Health Check; NHS England, Diabetes Prevention Programme. High blood sugar · Low blood sugar · DKA · Type 1 symptoms · Health Check · NHS DPP
- NHS labs: Bristol and Weston Chemical Pathology, Clinical Guideline for Diagnosis of Diabetes Mellitus; Royal Devon and Exeter, Diagnosis of Diabetes Guideline, 2016. North Bristol (PDF) · Royal Devon (PDF)
- University Hospitals of North Midlands (NHS) pathology. HbA1c. uhnm.nhs.uk
- Labcorp. Hemoglobin (Hb) A1c, test 001453. labcorp.com
- Mayo Clinic Laboratories. SI unit conversion table (glucose: mg/dL × 0.05551 = mmol/L). mayocliniclabs.com
- Patient.info Professional. Gestational diabetes (summary of NICE NG3), 2022. patient.info
This page is for education only and isn’t medical advice, a diagnosis or a substitute for your own doctor, who knows your history. Reference ranges vary between laboratories. Always interpret results with a qualified clinician. See our medical disclaimer.
