The normal range for an eAG test is under 114 mg/dL, which corresponds to an A1C below 5.7%. Because eAG is calculated from A1C using the ADAG formula, the two numbers always move together, and the eAG cutoffs for prediabetes and diabetes simply translate the A1C thresholds into milligrams per deciliter.
The eAG Normal Range Defined
eAG (estimated average glucose) was introduced in 2008 after the ADAG study, which correlated measured 24-hour glucose profiles with A1C in 507 participants. The formula eAG (mg/dL) = 28.7 x A1C – 46.7 produces a value in the same units as a fingerstick meter. Under ADA criteria, the A1C normal range is under 5.7%, so the eAG normal range is under 114 mg/dL. Anything between 117 and 137 mg/dL is prediabetes, and 154 mg/dL or higher signals diabetes on a confirmed second test.
Those numbers are not exact because A1C is reported to the nearest 0.1%. An A1C of 5.6% yields an eAG of 114 mg/dL, while 5.7% jumps to 117 mg/dL. For practical purposes, treat the normal upper limit as “about 115 mg/dL” and anything above that as worth a conversation with your clinician.
Full eAG Range Chart
| A1C (%) | eAG (mg/dL) | eAG (mmol/L) | Classification |
|---|---|---|---|
| 4.5 | 83 | 4.6 | Normal (low) |
| 5.0 | 97 | 5.4 | Normal |
| 5.5 | 111 | 6.2 | Normal |
| 5.7 | 117 | 6.5 | Prediabetes |
| 6.0 | 126 | 7.0 | Prediabetes |
| 6.4 | 137 | 7.6 | Prediabetes (upper) |
| 6.5 | 140 | 7.8 | Diabetes |
| 7.0 | 154 | 8.6 | Diabetes |
| 8.0 | 183 | 10.2 | Diabetes (uncontrolled) |
What to Expect from the Test
Because eAG is a derived number, you do not order an eAG test separately. You order an A1C, and the lab reports both values. The draw is a standard venipuncture or fingerstick capillary sample. Results return in minutes for point-of-care analyzers or within a business day for reference labs. Your report will typically show “HbA1c: 5.8%, eAG: 120 mg/dL” on the same line.
How to Prepare
No fasting is required. A1C measures the percentage of hemoglobin that has become permanently glycated over the lifespan of your red blood cells (about 120 days), so a meal, coffee, or workout in the hours before the draw cannot affect the result. Continue your regular medications and hydration. Mention any recent blood transfusion, chronic anemia, hemoglobinopathy (such as sickle cell trait), chemotherapy, or pregnancy to your clinician, because all of these can distort A1C and, by extension, eAG.
Normal vs. Prediabetes vs. Diabetes eAG Ranges
The table below breaks each classification into finer A1C increments so you can see exactly where your eAG falls within its category. Each row uses the ADAG formula endorsed by the ADA.
| Category | A1C Range (%) | eAG Range (mg/dL) | eAG Range (mmol/L) | What It Means |
|---|---|---|---|---|
| Normal (optimal) | 4.0 – 5.0 | 68 – 97 | 3.8 – 5.4 | Glucose metabolism is healthy; retest in 3 years unless risk factors change. |
| Normal (upper) | 5.1 – 5.6 | 100 – 114 | 5.6 – 6.3 | Still within normal limits, but above 5.4% warrants annual screening if overweight or over 45. |
| Prediabetes (lower) | 5.7 – 5.9 | 117 – 123 | 6.5 – 6.8 | Early prediabetes; lifestyle intervention is most effective at this stage. |
| Prediabetes (mid) | 6.0 – 6.2 | 126 – 131 | 7.0 – 7.3 | Moderate prediabetes; consider structured programs like the Diabetes Prevention Program. |
| Prediabetes (upper) | 6.3 – 6.4 | 134 – 137 | 7.4 – 7.6 | High-risk prediabetes; some clinicians discuss metformin alongside lifestyle changes. |
| Diabetes | 6.5+ | 140+ | 7.8+ | Diabetes threshold; requires confirmation with a second test on a different day. |
Because eAG is a direct mathematical conversion of A1C, the two always move in lockstep. A change of 0.5 percentage points in A1C shifts eAG by roughly 14 mg/dL.
How eAG Changes Over Three Months
A1C reflects glycated hemoglobin across the full lifespan of your red blood cells, which is approximately 120 days. However, the contribution is not evenly weighted. According to research published in Diabetes Care, about 50% of the A1C value comes from the most recent 30 days, roughly 25% from days 31 to 60, and the remaining 25% from days 61 to 120. That weighting means eAG responds to recent glucose changes faster than many people expect, but it also means a single week of very high or very low readings will not dramatically shift the number.
If you start a walking program and reduce refined carbohydrate intake today, your daily meter or CGM readings should improve within one to two weeks. The eAG on your next lab draw, ideally eight to twelve weeks later, will capture most of that improvement. A realistic target for the first cycle of lifestyle changes is a 0.3-0.5% drop in A1C, which translates to an eAG decrease of about 9-14 mg/dL. Larger drops are possible when starting from higher baseline levels.
When to Retest
ADA guidelines recommend the following retesting intervals based on your result category:
- Normal eAG (under 114 mg/dL): Retest every three years if you have no risk factors. If you are overweight, over 45, or have a family history of type 2 diabetes, retest annually.
- Prediabetes eAG (117-137 mg/dL): Retest every six to twelve months to track the direction of change. More frequent testing, such as every three months, is appropriate if you have recently started a lifestyle intervention and want to see early results.
- Diabetes-range eAG (140 mg/dL or above): Confirm with a repeat A1C or an oral glucose tolerance test. Once diabetes is diagnosed, A1C and eAG are typically checked every three months until glucose is stable, then every six months.
Retesting too soon, for example after only four weeks, will not give you a meaningful update because the older red blood cells from before your intervention are still circulating. Eight weeks is the minimum interval for a clinically interpretable change in A1C and eAG.
Accuracy of the eAG Calculation
The ADAG study found that 90% of participants had an eAG within about 15% of their actual measured average glucose. That is tight enough for clinical use but not perfect. People of African, African-American, or South Asian descent may have slightly higher A1C for the same glucose exposure, inflating eAG by 5-10 mg/dL. Continuous glucose monitor users often prefer the CGM-derived Glucose Management Indicator (GMI), which uses 10-14 days of sensor data instead of a single lab draw, offering a more personalized picture of glucose control.
What to Do with an Abnormal Result
If your eAG is between 117 and 137 mg/dL, you have prediabetes and should review your nutrition plan and weekly activity. Losing 5-7% of body weight cut progression to diabetes by 58% in the Diabetes Prevention Program. If eAG is 154 mg/dL or higher, confirm with a repeat test and start a treatment plan. See also our A1C levels hub for deeper detail.
The Bottom Line
A normal eAG test result sits below 114 mg/dL, mirroring an A1C under 5.7%. Values from 117 to 137 mg/dL signal prediabetes, and 154 mg/dL or higher meets the diabetes threshold when confirmed. eAG is a translation of A1C, not a standalone test, and it requires no fasting or special preparation.
