What does my A1c mean?
Your A1c is the share of hemoglobin in your red blood cells with sugar stuck to it. Put yours in for your average, your band and when a change will show.
Prediabetes range
NormalPrediabetes rangeDiabetes range
An A1c of 5.7% fits an average anywhere from 93 to 142 mg/dL, about 117 in the middle.
The 95% range in the ADAG study, 507 adults with 3 months of sensor and finger-stick data each (Nathan 2008, Table 2). People with the same A1c can have quite different averages.
When a change will show
Change your habits today and about half of a lasting change shows in your A1c within 5 weeks, most of it by 12. A1c leans on the last 100 days, the latest weeks most.
From a half-time of about 35 days in 9 people newly diagnosed with type 2 (Tahara and Shima 1995). That's why the retest goes at about 12 weeks.
A1c can mislead with anemia, sickle cell trait and some other blood conditions, so pair it with a fasting glucose.
Add a fasting glucose and fasting insulin for HOMA-IR
Type both numbers from the same morning's lab report.
Fasting glucose times fasting insulin, divided by 405. There's no cutoff here on purpose: published ones vary by population and by the lab's insulin test, so compare yours with your own earlier results.
The A1c chart
Every A1c from 4.5 to 10.0, with the average glucose it stands for and its US band. Under 5.7% is normal, 5.7 to 6.4% is the prediabetes range, and 6.5% or more on two tests is diabetes.
| A1c | mmol/mol | Average glucose | Range that fits | Band |
|---|---|---|---|---|
| 4.5% | 26 | 82 mg/dL 4.6 mmol/L | Normal | |
| 4.6% | 27 | 85 mg/dL 4.7 mmol/L | Normal | |
| 4.7% | 28 | 88 mg/dL 4.9 mmol/L | Normal | |
| 4.8% | 29 | 91 mg/dL 5.0 mmol/L | Normal | |
| 4.9% | 30 | 94 mg/dL 5.2 mmol/L | Normal | |
| 5.0% | 31 | 97 mg/dL 5.4 mmol/L | 76 to 120 | Normal |
| 5.1% | 32 | 100 mg/dL 5.5 mmol/L | 78 to 123 | Normal |
| 5.2% | 33 | 103 mg/dL 5.7 mmol/L | 81 to 126 | Normal |
| 5.3% | 34 | 105 mg/dL 5.8 mmol/L | 83 to 130 | Normal |
| 5.4% | 36 | 108 mg/dL 6.0 mmol/L | 86 to 133 | Normal |
| 5.5% | 37 | 111 mg/dL 6.2 mmol/L | 88 to 136 | Normal |
| 5.6% | 38 | 114 mg/dL 6.3 mmol/L | 90 to 139 | Normal |
| 5.7% | 39 | 117 mg/dL 6.5 mmol/L | 93 to 142 | Prediabetes range |
| 5.8% | 40 | 120 mg/dL 6.6 mmol/L | 95 to 146 | Prediabetes range |
| 5.9% | 41 | 123 mg/dL 6.8 mmol/L | 98 to 149 | Prediabetes range |
| 6.0% | 42 | 126 mg/dL 7.0 mmol/L | 100 to 152 | Prediabetes range |
| 6.1% | 43 | 128 mg/dL 7.1 mmol/L | 102 to 155 | Prediabetes range |
| 6.2% | 44 | 131 mg/dL 7.3 mmol/L | 105 to 159 | Prediabetes range |
| 6.3% | 45 | 134 mg/dL 7.4 mmol/L | 107 to 162 | Prediabetes range |
| 6.4% | 46 | 137 mg/dL 7.6 mmol/L | 109 to 165 | Prediabetes range |
| 6.5% | 48 | 140 mg/dL 7.7 mmol/L | 112 to 169 | Diabetes range |
| 6.6% | 49 | 143 mg/dL 7.9 mmol/L | 114 to 172 | Diabetes range |
| 6.7% | 50 | 146 mg/dL 8.1 mmol/L | 116 to 175 | Diabetes range |
| 6.8% | 51 | 148 mg/dL 8.2 mmol/L | 118 to 178 | Diabetes range |
| 6.9% | 52 | 151 mg/dL 8.4 mmol/L | 121 to 182 | Diabetes range |
| 7.0% | 53 | 154 mg/dL 8.5 mmol/L | 123 to 185 | Diabetes range |
| 7.1% | 54 | 157 mg/dL 8.7 mmol/L | 125 to 188 | Diabetes range |
| 7.2% | 55 | 160 mg/dL 8.9 mmol/L | 128 to 191 | Diabetes range |
| 7.3% | 56 | 163 mg/dL 9.0 mmol/L | 130 to 195 | Diabetes range |
| 7.4% | 57 | 166 mg/dL 9.2 mmol/L | 133 to 198 | Diabetes range |
| 7.5% | 58 | 169 mg/dL 9.3 mmol/L | 135 to 201 | Diabetes range |
| 7.6% | 60 | 171 mg/dL 9.5 mmol/L | 137 to 204 | Diabetes range |
| 7.7% | 61 | 174 mg/dL 9.7 mmol/L | 140 to 207 | Diabetes range |
| 7.8% | 62 | 177 mg/dL 9.8 mmol/L | 142 to 211 | Diabetes range |
| 7.9% | 63 | 180 mg/dL 10.0 mmol/L | 145 to 214 | Diabetes range |
| 8.0% | 64 | 183 mg/dL 10.1 mmol/L | 147 to 217 | Diabetes range |
| 8.1% | 65 | 186 mg/dL 10.3 mmol/L | 149 to 220 | Diabetes range |
| 8.2% | 66 | 189 mg/dL 10.4 mmol/L | 152 to 223 | Diabetes range |
| 8.3% | 67 | 192 mg/dL 10.6 mmol/L | 154 to 227 | Diabetes range |
| 8.4% | 68 | 194 mg/dL 10.8 mmol/L | 156 to 230 | Diabetes range |
| 8.5% | 69 | 197 mg/dL 10.9 mmol/L | 159 to 233 | Diabetes range |
| 8.6% | 70 | 200 mg/dL 11.1 mmol/L | 161 to 236 | Diabetes range |
| 8.7% | 72 | 203 mg/dL 11.2 mmol/L | 163 to 239 | Diabetes range |
| 8.8% | 73 | 206 mg/dL 11.4 mmol/L | 165 to 243 | Diabetes range |
| 8.9% | 74 | 209 mg/dL 11.6 mmol/L | 168 to 246 | Diabetes range |
| 9.0% | 75 | 212 mg/dL 11.7 mmol/L | 170 to 249 | Diabetes range |
| 9.1% | 76 | 214 mg/dL 11.9 mmol/L | 172 to 252 | Diabetes range |
| 9.2% | 77 | 217 mg/dL 12.0 mmol/L | 175 to 256 | Diabetes range |
| 9.3% | 78 | 220 mg/dL 12.2 mmol/L | 177 to 259 | Diabetes range |
| 9.4% | 79 | 223 mg/dL 12.4 mmol/L | 179 to 262 | Diabetes range |
| 9.5% | 80 | 226 mg/dL 12.5 mmol/L | 182 to 266 | Diabetes range |
| 9.6% | 81 | 229 mg/dL 12.7 mmol/L | 184 to 269 | Diabetes range |
| 9.7% | 83 | 232 mg/dL 12.8 mmol/L | 186 to 272 | Diabetes range |
| 9.8% | 84 | 235 mg/dL 13.0 mmol/L | 188 to 275 | Diabetes range |
| 9.9% | 85 | 237 mg/dL 13.2 mmol/L | 191 to 279 | Diabetes range |
| 10.0% | 86 | 240 mg/dL 13.3 mmol/L | 193 to 282 | Diabetes range |
How it works
Average glucose comes from the ADAG study, which followed 507 adults for 3 months with sensors and finger sticks: 28.7 times A1c, minus 46.7, in mg/dL. The range beside it is the study's 95% range, so an A1c of 6% fits an average anywhere from 100 to 152. mmol/mol is the international unit, from the NGSP master equation.
GMI does the same job for a sensor's average, with a formula from Dexcom users with diabetes. A sensor runs high, so a healthy person's average of 98 gives a GMI of 5.7, the first prediabetes number. That's the formula and the sensor, not prediabetes. Trust the lab A1c.
A1c moves slowly. After blood sugar came down in 9 people newly diagnosed with type 2, it fell with a half-time of about 35 days, weighted back about 100 days, so a retest at about 12 weeks shows most of a change. HOMA-IR, folded under the converter, multiplies a fasting glucose by a fasting insulin. It comes with no cutoff, because published ones vary by population and by lab.
7 sources
- American Diabetes Association, Standards of Care in Diabetes 2026, section 2, Diagnosis and Classification, Tables 2.1 and 2.2pmc.ncbi.nlm.nih.gov
- Nathan DM and others, Translating the A1C assay into estimated average glucose values, Diabetes Care, 2008pmc.ncbi.nlm.nih.gov
- NGSP, IFCC and NGSP master equationngsp.org
- Bergenstal RM and others, Glucose Management Indicator (GMI): a new term for estimating A1C from continuous glucose monitoring, Diabetes Care, 2018pmc.ncbi.nlm.nih.gov
- Bergenstal and others, an updated glucose management indicator, Diabetologia, 2026pubmed.ncbi.nlm.nih.gov
- Tahara Y and Shima K, Kinetics of HbA1c, glycated albumin, and fructosamine, Diabetes Care, 1995pubmed.ncbi.nlm.nih.gov
- Biernacka-Bartnik and others, HOMA-IR, 2023pmc.ncbi.nlm.nih.gov
