Quick answer: the A1C normal range is under 5.7% (under 39 mmol/mol); 5.7% to 6.4% (39 to 47 mmol/mol) is prediabetes and 6.5% (48 mmol/mol) or higher meets the diabetes threshold (ADA Standards of Care 2026; CDC). For many adults with diabetes, the treatment goal is under 7% (MedlinePlus). The cutoffs are the same at every adult age; a diagnosis needs a repeat test or a second test unless blood sugar is clearly very high.
A1C normal range and chart
| A1C (%) | A1C (mmol/mol) | Estimated average glucose | Category |
|---|---|---|---|
| 5.0% | 31 | 97 mg/dL | Normal |
| 5.6% | 38 | 114 mg/dL | Normal |
| 5.7% | 39 | 117 mg/dL | Prediabetes starts |
| 6.0% | 42 | 126 mg/dL | Prediabetes |
| 6.4% | 46 | 137 mg/dL | Prediabetes |
| 6.5% | 48 | 140 mg/dL | Diabetes threshold |
| 7.0% | 53 | 154 mg/dL | Common treatment goal is under this |
| 8.0% | 64 | 183 mg/dL | Diabetes range |
Categories from the ADA and CDC. Estimated average glucose (eAG) uses the ADAG study formula, eAG (mg/dL) = 28.7 x A1C - 46.7 (Diabetes Care, 2008); divide by 18 for mmol/L. The mmol/mol column is the IFCC unit used outside the US. MedlinePlus notes that real glucose readings are usually more reliable than an eAG calculated from A1C.
ADAG formula, eAG = 28.7 x A1C - 46.7 (Nathan et al, Diabetes Care 2008). These are estimates, not measured glucose.
What is HbA1c?
Hemoglobin A1c is the share of your hemoglobin (the oxygen-carrying protein in red blood cells) that has glucose stuck to it. Red cells live for a few months, so the percentage reflects your average blood sugar over roughly the past two to three months rather than today's reading. That is why it is used both to diagnose diabetes and to track how well it is controlled. It does not need fasting and is not thrown off by one sweet meal.
What a high A1C means
- 5.7% to 6.4%, prediabetes: blood sugar is higher than normal but below the diabetes line. This is the range where lifestyle change has the most room to help.
- 6.5% or higher: the ADA's diabetes threshold. Without clear symptoms of very high blood sugar, a doctor confirms it with a repeat A1C or a different test, such as fasting glucose (126 mg/dL or more) or a 2-hour glucose tolerance test (200 mg/dL or more).
- Above your goal, with diabetes: a sign treatment may need adjusting. Doctors set individual goals, often under 7% for many adults.
High blood sugar also tends to travel with high triglycerides, low HDL and a raised ApoB, so a high A1C is a reason to look at your lipids too.
Worked example: an A1C of 6.1%
Say a 48-year-old man with a BMI of 32 gets an A1C of 6.1% from a home kit. That is inside the 5.7% to 6.4% prediabetes band, 0.4 points above normal and 0.4 below the diabetes threshold. By the ADAG formula it equals an estimated average glucose of about 128 mg/dL (28.7 x 6.1 - 46.7), and in IFCC units it is about 43 mmol/mol.
What might explain it: excess weight and low activity are the usual drivers of insulin resistance at his age. It is also worth ruling out anything that skews A1C itself, such as anemia or low iron stores.
Questions to take to his doctor:
- Should we confirm this with a repeat A1C or a fasting glucose (the ADA diabetes line is 126 mg/dL fasting)?
- Could anemia or anything in the "When A1C can be wrong" list below affect my result? Should I check ferritin?
- What weight and activity changes should I aim for, and should we retest in about three months?
- Should my lipids, including ApoB, be checked too?
What a low A1C means
There is no diagnostic lower cutoff for people without diabetes, and a low-normal A1C is usually fine. If your A1C does not match your glucose readings, in either direction, one of the conditions in the next section may be distorting it. If you take diabetes medication and your A1C is falling fast, check with your doctor that your treatment is still right for you.
When A1C can be wrong
Because A1C depends on red blood cells, anything that changes them can skew it. MedlinePlus and the CDC list:
- Anemia, including severe iron deficiency (check ferritin)
- Kidney failure and liver disease
- Hemoglobin variants and blood disorders such as sickle cell disease and thalassemia
- Recent blood loss or a transfusion
- Early or late pregnancy
- Some medicines, including opioids and some HIV medications
If any of these apply, tell your doctor; they may use glucose tests instead.
What lowers A1C
- Weight: losing excess weight improves insulin sensitivity.
- Activity: muscle uses glucose, so regular exercise lowers average blood sugar.
- Diet: fewer sugary drinks and refined carbs.
- Medication: if you have diabetes or high-risk prediabetes, medication may be part of the plan. Talk to your doctor before changing anything.
Since A1C reflects about three months, retest roughly every three months to see the effect of a change. For how well your pancreas is keeping up, C-peptide adds a second angle.
How to test A1C
A1C is a routine blood test. No fasting is needed; MedlinePlus says recent meals do not affect it, and the CDC agrees, though other tests drawn at the same time may need a fast. Fingertip meters give a result in minutes; mail-in kits send blood to a lab. Our at-home A1C test guide compares both routes.
Which at-home tests include A1C
HbA1c is on four SiPhox panels: Longevity Essentials, Heart & Metabolic, Ultimate 360 and GLP Optimization. Thyroid Focus and Hormone Focus do not include it.
| SiPhox panel | Biomarkers per test | Per test, with shipping | Listed as |
|---|---|---|---|
| Longevity Essentials | 31 | $149 | HbA1c (Metabolic) |
| Heart & Metabolic | 28 | $149 | HbA1c (Metabolic) |
| Ultimate 360 | 62 | $274 | HbA1c (Metabolic) |
| GLP Optimization | 46 | $224 | HbA1c (Metabolic) |
Longevity Essentials, GLP Optimization and Ultimate 360 also report estimated average glucose, and all four include C-peptide. SiPhox does not measure glucose on its EasyDraw panels, and it measures C-peptide rather than fasting insulin, so it cannot give you a HOMA-IR score. Collection is from the upper arm at home; results come without an included doctor review, so discuss anything in the prediabetes or diabetes range with your doctor. If you take a GLP-1 medicine, see our GLP-1 blood test page; otherwise start with our SiPhox review.
Longevity Essentials
The default panel: heart, metabolic, hormone and inflammation markers in one draw.
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Heart & Metabolic
Lipids plus kidney and liver function: the panel for cardiovascular and metabolic risk.
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GLP Optimization
Built for people on GLP-1 medication: metabolic, liver, kidney, nutrient and iron markers.
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Frequently asked questions
What is a normal A1C level?
Under 5.7% (39 mmol/mol), according to the ADA and CDC. 5.7% to 6.4% is prediabetes and 6.5% or higher is the diabetes threshold.
Does normal A1C change with age?
No. The diagnostic cutoffs are the same for all adults. What changes is the treatment goal a doctor may set for an older adult who already has diabetes.
Do you need to fast for an A1C test?
No. MedlinePlus and the CDC both say fasting is not needed because recent food does not affect A1C.
What average blood sugar is an A1C of 6%?
About 126 mg/dL (7.0 mmol/L), using the ADAG formula eAG = 28.7 x A1C - 46.7.
Can anemia affect A1C?
Yes. Anemia, kidney or liver disease, hemoglobin variants, blood loss, transfusion and pregnancy can all make A1C less accurate (MedlinePlus; CDC).
Sources
- American Diabetes Association. 2. Diagnosis and classification of diabetes: Standards of Care in Diabetes 2026. Diabetes Care 2026
- American Diabetes Association. 6. Glycemic goals, hypoglycemia and hyperglycemic crises: Standards of Care in Diabetes 2026
- CDC: A1C test for diabetes and prediabetes
- MedlinePlus: A1C test
- Nathan DM et al. Translating the A1C assay into estimated average glucose values. Diabetes Care 2008
- SiPhox Health: panel comparison and biomarker lists (checked 29 Sep 2026)