Because Hemoglobin A1c is reported as a percentage, patients often struggle to connect their lab result with daily fingerstick or continuous glucose monitor (CGM) readings. Using the validated ADAG mathematical formula, an A1c percentage directly converts into an Estimated Average Glucose (eAG) in mg/dL or mmol/L. For example, an A1c of 5.0% equals an average daily glucose of 97 mg/dL, while an A1c of 6.0% equals 126 mg/dL.
When you check your blood sugar on a daily home glucose meter or Continuous Glucose Monitor (CGM), the number is reported in milligrams per deciliter (mg/dL) or millimoles per liter (mmol/L).
When your physician orders a blood test, however, the lab reports your Hemoglobin A1c (HbA1c) as a percentage, such as 5.6%, 6.1%, or 6.8%.
This difference in units creates confusion: What daily blood sugar average does a 6.0% A1c actually represent? How do I translate my 3-month percentage into daily glucose numbers?
Here is the official ADAG conversion formula, the complete master clinical chart, and why your CGM reading might differ slightly from your lab blood draw.
The ADAG Mathematical Conversion Formula#
eAG (mg/dL) = 28.7 × HbA1c - 46.7
eAG (mmol/L) = 1.59 × HbA1c - 2.59
For every 1.0% increase in your HbA1c, your daily average blood sugar increases by approximately 29 mg/dL (1.6 mmol/L).
Master A1c to eAG Clinical Conversion Table#
| HbA1c (%) | Estimated Average Glucose (mg/dL) | Estimated Average Glucose (mmol/L) | Clinical & Longevity Category |
|---|---|---|---|
| 4.5% | 83 mg/dL | 4.6 mmol/L | Optimal Longevity Range |
| 4.8% | 91 mg/dL | 5.1 mmol/L | Optimal Longevity Range |
| 5.0% | 97 mg/dL | 5.4 mmol/L | Optimal Longevity Range |
| 5.2% | 103 mg/dL | 5.7 mmol/L | Optimal Longevity Range |
| 5.4% | 108 mg/dL | 6.0 mmol/L | Standard Normal (High-Normal) |
| 5.6% | 114 mg/dL | 6.3 mmol/L | Standard Normal (High-Normal) |
| 5.7% | 117 mg/dL | 6.5 mmol/L | Prediabetes Diagnostic Floor |
| 5.8% | 120 mg/dL | 6.7 mmol/L | Prediabetes |
| 6.0% | 126 mg/dL | 7.0 mmol/L | Prediabetes |
| 6.1% | 128 mg/dL | 7.1 mmol/L | Prediabetes |
| 6.3% | 134 mg/dL | 7.4 mmol/L | Prediabetes |
| 6.4% | 137 mg/dL | 7.6 mmol/L | Upper Prediabetes Threshold |
| 6.5% | 140 mg/dL | 7.8 mmol/L | Clinical Diabetes Diagnostic Floor |
| 7.0% | 154 mg/dL | 8.6 mmol/L | ADA Treatment Goal for Diabetics |
| 8.0% | 183 mg/dL | 10.2 mmol/L | Uncontrolled Hyperglycemia |
| 9.0% | 212 mg/dL | 11.8 mmol/L | Severe Hyperglycemia |
Why Your CGM Glucose Management Indicator (GMI) Might Differ from Lab A1c#
If you wear a Continuous Glucose Monitor (Dexcom, FreeStyle Libre), your app provides an estimated metric called the Glucose Management Indicator (GMI).
Frequently, your lab-drawn HbA1c differs from your CGM GMI by 0.2% to 0.5%:
- Interstitial Fluid vs. Venous Blood: CGMs measure glucose in subcutaneous interstitial fluid, which has a 5-to-10-minute biological lag behind capillary and venous blood.
- Individual Red Blood Cell Lifespan: The standard A1c formula assumes an average erythrocyte lifespan of 115 days. If your red blood cells naturally live 100 days or 130 days, your glycation percentage will be lower or higher, respectively, independent of your actual average glucose.
- Sensor Calibration: Minor drift in sensor enzyme accuracy over a 10-to-14-day wear period can skew calculations slightly.
Two individuals can have the exact same 5.7% A1c (average 117 mg/dL), but completely different cardiovascular risk profiles. A person with steady glucose between 90 and 130 mg/dL has far less endothelial inflammation than someone whose blood sugar swings wildly between 60 mg/dL (hypoglycemia) and 200 mg/dL (hyperglycemia).
To learn how to lower your A1c through evidence-based dietary protocols, read How to Lower A1c Fast: 5 Evidence-Based Protocols.
Track Your Health & Glycemic Biomarkers with Meridian#
Monitoring your laboratory blood biomarkers over time gives you objective validation that your diet, exercise, and lifestyle habits are keeping your A1c in the optimal longevity range.
Meridian is an offline personal health vault for iPhone designed to give you complete ownership of your medical diagnostic data.
- Instant Lab Report Extraction: Take a photo or upload a PDF of your Comprehensive Metabolic Panel, lipid panels, and HbA1c reports from Quest, Labcorp, or your clinic. Meridian extracts your biomarkers on-device using Apple VisionKit.
- Longitudinal Glycemic Trends: Track how your fasting glucose, HbA1c, and liver enzymes (ALT & AST) improve over years.
- On-Device Biological Age: In our upcoming update, calculate how glycemic stability lowers your cellular biological age with zero cloud uploads.
- 100% On-Device & Private: Protected by hardware AES-256 encryption and FaceID. Zero cloud servers. Zero data tracking.
Take control of your metabolic health and medical privacy today. Download Meridian on the App Store and keep your diagnostic records organized, private, and secure.