What is estimated average glucose?

Estimated average glucose (eAG) translates an HbA1c into the average blood glucose it corresponds to over the preceding two to three months. It gives patients a number in the same units as their day-to-day meter readings.

What formula does the tool use?

It uses the ADAG study regression: eAG in mg/dL equals 28.7 times the HbA1c percent minus 46.7. The mmol/L value is the mg/dL result divided by 18.018. These are the equations adopted for reporting A1c-derived average glucose.

How do NGSP percent and IFCC mmol/mol relate?

They are two scales for the same measurement. NGSP percent equals the IFCC mmol/mol value divided by 10.929 plus 2.15. For example 53 mmol/mol corresponds to about 7.0 percent.

When is eAG unreliable?

HbA1c reflects red-cell glucose exposure over the cell's lifespan, so anything that shortens or alters that lifespan distorts it. Anaemia, haemoglobinopathies, recent transfusion, pregnancy, and kidney disease can all make eAG misleading.

Why does eAG sometimes differ from my meter average?

eAG is a population regression, so an individual's true average can sit above or below it. It also weights recent glucose more heavily. Use it as a guide for discussion, not an exact match to a meter or sensor average.

HbA1c to Average Glucose Converter (eAG)

Reporting an HbA1c as an estimated average glucose helps patients relate a lab percentage to the glucose numbers they see on a meter or sensor. This converter moves between the NGSP percent and IFCC mmol/mol scales and applies the ADAG regression to give an average glucose in both common units, all in your browser.

How it works

The tool first puts your HbA1c onto the NGSP percent scale, then applies the ADAG study regression:

NGSP%        = IFCC_mmol_per_mol / 10.929 + 2.15
eAG (mg/dL)  = 28.7 × HbA1c% − 46.7
eAG (mmol/L) = eAG_mgdl / 18.018

The same relationships run in reverse to report the IFCC value alongside the percent. The regression is the one adopted internationally for translating A1c into an average glucose.

Example and notes

An HbA1c of 7.0% (53 mmol/mol) gives an estimated average glucose of 28.7 × 7.0 − 46.7 = 154 mg/dL, or about 8.6 mmol/L. That is why a 7% target is often described as an average glucose around 8.5 mmol/L. Remember that HbA1c integrates glucose over the red cell’s lifespan, so it can mislead in anaemia, haemoglobinopathies, pregnancy, or after a recent transfusion. eAG is a population estimate — an individual’s measured average may differ.