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Estimated Average Glucose Calculator

Free Estimated average glucose Calculator with medically-sourced formulas. Enter your measurements for personalized, accurate health insights.

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Formula

eAG (mg/dL) = 28.7 x HbA1c - 46.7 | eAG (mmol/L) = 1.59 x HbA1c - 2.59

The ADAG (A1c-Derived Average Glucose) formula was derived from a study of 507 participants using continuous glucose monitoring. It converts the HbA1c percentage to an estimated average glucose that corresponds to the mean glucose over the prior 2-3 months. The IFCC conversion is: mmol/mol = (NGSP% - 2.15) x 10.929.

Worked Examples

Example 1: Well-Controlled Diabetes Assessment

Problem: A patient with Type 2 diabetes has an HbA1c of 6.8%. Their home glucose readings show fasting of 110 mg/dL and post-meal of 145 mg/dL. Calculate eAG and assess control.

Solution: eAG (ADAG formula) = 28.7 x 6.8 - 46.7 = 195.16 - 46.7 = 148.5 mg/dL\neAG in mmol/L = 148.5 / 18.0182 = 8.24 mmol/L\nIFCC A1c = (6.8 - 2.15) x 10.929 = 50.8 mmol/mol\n\nHome average = (110 + 145) / 2 = 127.5 mg/dL\nDiscrepancy = 127.5 - 148.5 = -21.0 mg/dL (home readings lower than eAG)\n\nA1c target assessment: 6.8% is below 7.0% target\nEstimated time in range: approximately 73%

Result: eAG: 148.5 mg/dL (8.24 mmol/L) | At ADA Target (<7%) | Prediabetes-Diabetes border | Good control

Example 2: Poorly Controlled Diabetes Assessment

Problem: A patient has HbA1c of 9.5%. Home fasting glucose averages 200 mg/dL and post-meal 280 mg/dL. Calculate eAG and determine management implications.

Solution: eAG (ADAG formula) = 28.7 x 9.5 - 46.7 = 272.65 - 46.7 = 226.0 mg/dL\neAG in mmol/L = 226.0 / 18.0182 = 12.54 mmol/L\nIFCC A1c = (9.5 - 2.15) x 10.929 = 80.3 mmol/mol\n\nHome average = (200 + 280) / 2 = 240.0 mg/dL\nDiscrepancy = 240.0 - 226.0 = +14.0 mg/dL (home readings slightly higher)\n\nA1c target: 9.5% is 2.5% above 7.0% target\nEstimated time in range: approximately 22%

Result: eAG: 226.0 mg/dL (12.54 mmol/L) | 2.5% above target | Urgent medication intensification needed

Frequently Asked Questions

What is estimated average glucose and how is it calculated from HbA1c?

Estimated average glucose (eAG) is a calculation that converts the HbA1c percentage into an approximate average blood glucose value in mg/dL or mmol/L, making HbA1c results more intuitive for patients and clinicians. The ADAG (A1c-Derived Average Glucose) study, published in 2008, established the definitive relationship using continuous glucose monitoring data from 507 participants across 10 international centers. The resulting formula is eAG (mg/dL) = 28.7 multiplied by HbA1c minus 46.7, or equivalently eAG (mmol/L) = 1.59 multiplied by HbA1c minus 2.59. For example, an HbA1c of 7.0% corresponds to an eAG of approximately 154 mg/dL (8.6 mmol/L). This conversion helps bridge the communication gap between the laboratory measurement (HbA1c) and the daily glucose values that patients monitor at home.

How does estimated time in range relate to HbA1c values?

Time in range (TIR) is a newer metric from continuous glucose monitoring that measures the percentage of time glucose values stay between 70 and 180 mg/dL (3.9 to 10.0 mmol/L). Research has established an approximate correlation between TIR and HbA1c. A TIR of 70% (the recommended target for most adults with diabetes) corresponds roughly to an HbA1c of 7.0%. Each 10 percentage point increase in TIR corresponds to approximately 0.5% decrease in HbA1c. For example, TIR of 50% approximates HbA1c of 8.0%, while TIR of 80% approximates 6.5%. However, this relationship is imperfect because two patients with identical HbA1c values can have very different TIR percentages due to differences in glucose variability. A patient with wide glucose swings (high glycemic variability) may have the same HbA1c as a patient with stable glucose but very different TIR and clinical outcomes.

Why might there be a discrepancy between home glucose readings and eAG from HbA1c?

Discrepancies between home glucose monitoring averages and eAG derived from HbA1c are extremely common and have multiple explanations. First, fingerstick testing typically captures only 4 to 8 daily snapshots while HbA1c reflects the entire 24-hour glucose profile including overnight values that patients rarely measure. Second, most patients test preferentially before meals (when glucose tends to be lower) and may miss significant post-meal spikes. Third, biological variation in glycation rates means some individuals are high glycators who attach glucose to hemoglobin more readily, producing higher HbA1c relative to their actual average glucose. Conversely, low glycators have lower HbA1c than expected. Fourth, the conditions mentioned previously (anemia, hemoglobin variants, kidney disease) can skew HbA1c. When discrepancies are consistently large, clinicians should consider CGM data, fructosamine testing, or glycated albumin as complementary measures of glycemic control.

How is GFR estimated and what does it indicate?

Glomerular Filtration Rate estimates kidney function. The CKD-EPI equation uses creatinine, age, and sex. Normal GFR is above 90 mL/min/1.73m^2. Stages: 60-89 (mild decrease), 30-59 (moderate), 15-29 (severe), below 15 (kidney failure). GFR guides medication dose adjustments for renally-cleared drugs.

What formula does Estimated Average Glucose Calculator use?

The formula used is described in the Formula section on this page. It is based on widely accepted standards in the relevant field. If you need a specific reference or citation, the References section provides links to authoritative sources.

How do I get the most accurate result?

Enter values as precisely as possible using the correct units for each field. Check that you have selected the right unit (e.g. kilograms vs pounds, meters vs feet) before calculating. Rounding inputs early can reduce output precision.

References