Estimated Average Glucose Calculator

Estimated average glucose, or eAG, translates an HbA1c laboratory result into the same glucose units used by blood glucose meters and continuous glucose monitors. HbA1c reflects the proportion of hemoglobin with glucose attached and summarizes exposure over roughly the previous two to three months, with recent weeks contributing more strongly. Because a percentage can feel abstract, expressing that result as an average glucose often makes conversations about diabetes monitoring easier to understand. The calculator uses the widely cited ADAG relationship: eAG in mg/dL equals 28.7 multiplied by HbA1c, minus 46.7. To show metric units, the mg/dL result is divided by 18. An HbA1c of 7.0%, for example, corresponds to approximately 154.2 mg/dL or 8.6 mmol/L. The relationship is linear, so each one percentage-point increase in HbA1c adds about 28.7 mg/dL to estimated average glucose. An eAG value is not the same as the arithmetic mean of every home reading. Finger-stick testing may emphasize fasting or premeal measurements and miss overnight or after-meal changes. Continuous monitors sample much more often, but their glucose management indicator is calculated differently and can diverge from laboratory HbA1c. eAG is best understood as a population-based translation of HbA1c, not a prediction of any single glucose reading. Several conditions can weaken the relationship. Hemoglobin variants, anemia, recent bleeding or transfusion, pregnancy, advanced kidney disease, altered red blood cell lifespan, and some medications may change HbA1c independently of average glucose. Rapid improvements or deteriorations can also create a mismatch because HbA1c remains weighted across prior weeks. When laboratory HbA1c and glucose records disagree, a clinician may review assay limitations and consider fructosamine, glycated albumin, or continuous monitoring data. Diagnostic and treatment targets are individualized. Common educational examples place HbA1c below 5.7% in the usual nondiabetes range, 5.7% through 6.4% in the prediabetes range, and 6.5% or higher in the diabetes range when confirmed under appropriate clinical criteria. Many adults with diabetes have a general target near 7%, but age, pregnancy, hypoglycemia risk, other illness, and treatment burden can change the goal. Use the calculator to understand unit conversion and trends, then discuss interpretation and medication decisions with a qualified healthcare professional.