Blood sugar chart: normal, prediabetes and diabetes
These are the ranges used for adults who don't already have diabetes, from the U.S. Centers for Disease Control and Prevention (CDC). Prediabetes is sometimes called "borderline" diabetes. Use the checker to see where a test result falls.
A1C (HbA1c)
Your average blood sugar over the past 2 to 3 months. You don't need to fast for this test.
| Category | A1C % | mmol/mol |
|---|---|---|
| Normal | Below 5.7% | Below 39 |
| Prediabetes (borderline) | 5.7% to 6.4% | 39 to 47 |
| Diabetes range | 6.5% or higher | 48 or higher |
Fasting blood sugar
Measured after not eating or drinking anything except water for at least 8 hours, usually overnight.
| Category | mg/dL | mmol/L |
|---|---|---|
| Low blood sugar | Below 70 | Below 3.9 |
| Normal | 70 to 99 | 3.9 to 5.5 |
| Prediabetes (borderline) | 100 to 125 | 5.6 to 6.9 |
| Diabetes range | 126 or higher | 7.0 or higher |
2-hour glucose tolerance test
Measured 2 hours after drinking a sugary liquid at a clinic or lab, after fasting overnight.
| Category | mg/dL | mmol/L |
|---|---|---|
| Normal | Below 140 | Below 7.8 |
| Prediabetes (borderline) | 140 to 199 | 7.8 to 11.0 |
| Diabetes range | 200 or higher | 11.1 or higher |
mmol/L values are converted from mg/dL (divide by 18) and rounded, so labs may show slightly different cut-offs.
Good to know
- One result isn't a diagnosis. A doctor confirms diabetes with a repeat test, or two different tests.
- Prediabetes can often be turned around. Losing a small amount of weight if you're overweight and being more active lowers the chance of it becoming type 2 diabetes. A doctor can refer you to a lifestyle change programme.
- Already have diabetes? These ranges are for diagnosis, not treatment. Your doctor will give you your own blood sugar targets.
- Pregnancy and children use different tests and ranges. Ask your doctor or midwife.
- Low blood sugar (below 70 mg/dL or 3.9 mmol/L) can cause shakiness, sweating, a fast heartbeat, hunger or confusion. It mostly happens to people taking some diabetes medicines. If someone is confused, can't eat or drink safely, has a seizure or passes out, call 911 or your local emergency number.
- The CDC suggests an A1C test if you're over 45, or younger with overweight and another risk factor for type 2 diabetes.
This is not a diagnosis. Only a doctor can diagnose diabetes, usually by repeating the test on another day. Always talk to a doctor about your results before making any decision.
Sources
- Centers for Disease Control and Prevention (CDC): Diabetes testing
- CDC: A1C test for diabetes and prediabetes
- CDC: Low blood sugar (hypoglycemia)
- National Institute of Diabetes and Digestive and Kidney Diseases (NIH): The A1C test and diabetes
- MedlinePlus (U.S. National Library of Medicine): Hemoglobin A1C (HbA1c) test