HbA1c to Average Glucose Conversion Chart
The American Diabetes Association provides a standardized conversion table that translates HbA1c percentages into estimated average glucose levels, based on the ADAG study of 2,700 glucose measurements over 3 months in 507 adults, showing a strong correlation (r = 0.92) between HbA1c and mean glucose. 1, 2
Standard Conversion Table
| HbA1c (%) | Average Glucose (mg/dL) | Average Glucose (mmol/L) |
|---|---|---|
| 5% | 97 (76–120) | 5.4 (4.2–6.7) |
| 6% | 126 (100–152) | 7.0 (5.5–8.5) |
| 7% | 154 (123–185) | 8.6 (6.8–10.3) |
| 8% | 183 (147–217) | 10.2 (8.1–12.1) |
| 9% | 212 (170–249) | 11.8 (9.4–13.9) |
| 10% | 240 (193–282) | 13.4 (10.7–15.7) |
| 11% | 269 (217–314) | 14.9 (12.0–17.5) |
| 12% | 298 (240–347) | 16.5 (13.3–19.3) |
Values in parentheses represent 95% confidence intervals 1, 2
What a Glucose of 4.4 mmol/L Means
A fasting glucose of 4.4 mmol/L (79 mg/dL) falls within the normal non-diabetic range and would correspond to an estimated HbA1c of approximately 4.6–4.8%, which is below the non-diabetic reference range upper limit of 5.6%. 3
- Using the ADAG formula (eAG in mg/dL = 28.7 × HbA1c% - 46.7), a glucose of 79 mg/dL would reverse-calculate to an HbA1c of approximately 4.4–4.8% 2
- This glucose level indicates excellent glycemic control and is well below any diabetes or prediabetes threshold 3
Mathematical Formula for Conversion
The conversion formula is: Average Glucose (mg/dL) = 28.7 × HbA1c (%) - 46.7, allowing calculation of estimated average glucose from any HbA1c value. 2, 4
- This formula was derived from approximately 2,700 glucose measurements collected over three months per HbA1c value in the international ADAG study 1, 2
- An online calculator is available at professional.diabetes.org/eAG for easy conversion 1
Critical Limitations You Must Know
HbA1c-to-glucose conversions become invalid in patients with conditions affecting red blood cell turnover, including hemolytic anemia, recent blood transfusion, iron deficiency anemia, hemoglobinopathies (sickle cell disease, thalassemia), pregnancy, end-stage kidney disease, or use of erythropoiesis-stimulating agents—in these situations, use direct glucose monitoring instead. 2, 3
- Hemoglobin variants may interfere with some HbA1c assays, though most U.S. assays remain accurate for heterozygous common variants 2
- In sickle cell disease (HbSS) or other homozygous hemoglobin variants, HbA1c cannot be measured because individuals lack measurable HbA1c 2
- African American individuals may exhibit slightly higher HbA1c values than non-Hispanic White individuals for the same mean glucose level 2, 4
What This Conversion Does NOT Tell You
The estimated average glucose reflects only mean glucose concentration over 2–3 months and provides zero information about glycemic variability, hypoglycemia risk, glucose excursions, or day-to-day fluctuations. 1, 2, 3
- For patients with significant glycemic variability, particularly those with type 1 diabetes or type 2 diabetes with severe insulin deficiency, glycemic status is best evaluated by combining continuous glucose monitoring (CGM) or self-monitoring of blood glucose (SMBG) with HbA1c 1
- The ADAG data were collected in 2008 using early CGM systems, so derived estimates may not fully reflect the performance of contemporary CGM technologies 2
Clinical Context for Interpretation
The American Diabetes Association recommends an HbA1c goal of <7% (corresponding to average glucose <154 mg/dL or <8.6 mmol/L) for most nonpregnant adults with diabetes to reduce microvascular and neuropathic complications. 1
- HbA1c ≥6.5% (average glucose ≥126 mg/dL or ≥7.0 mmol/L) is the diagnostic threshold for diabetes when using NGSP-certified laboratory methods 3
- HbA1c values of 5.7–6.4% indicate prediabetes 3
- The correlation between HbA1c and average glucose is strongest when HbA1c is measured using standardized, NGSP-certified methods 5