Glucose management indicator (GMI)
Also called estimated A1C from CGM.
GMI turns the mean glucose from CGM data into a number on the A1C scale. It replaced the older name eA1C in 2018, because the result often differs from a lab A1C taken at the same time. In a 528-person sample, GMI and lab A1C differed by 0.5 points or more for 28% of people. (Bergenstal et al., GMI, 2018; ADA Standards of Care 2026, section 6)
Formula
GMI (%) = 3.31 + 0.02392 × mean glucose in mg/dL; GMI (mmol/mol) = 12.71 + 4.70587 × mean glucose in mmol/L
(Bergenstal et al., GMI, 2018)
Worked example
A 14-day mean of 154 mg/dL (8.5 mmol/L) gives GMI = 3.31 + 0.02392 × 154 = 7.0%, or 12.71 + 4.70587 × 8.548 = 53 mmol/mol.
Related terms
Sources, quoted
- Bergenstal et al., GMI, 2018: “This led the authors to work toward a multipart solution to facilitate the retention of such a metric, which includes renaming the eA1C the glucose management indicator (GMI) and generating a new formula for converting CGM-derived mean glucose to GMI based on recent clinical trials using the most accurate CGM systems available.”
- Bergenstal et al., GMI, 2018: “Table 3 shows the degree to which the GMI (calculated from CGM-derived mean glucose) and the A1C (laboratory measured) agree, based on 528 individuals with diabetes having both values measured concurrently.”
- Bergenstal et al., GMI, 2018: “≥0.5 28 24–32”
- Bergenstal et al., GMI, 2018: “The regression equation to compute GMI (%) = 3.31 + 0.02392 × [mean glucose in mg/dL] or GMI (mmol/mol) = 12.71 + 4.70587 × [mean glucose in mmol/L].”
- ADA Standards of Care 2026, section 6: “Calculated value approximating A1C (not always equivalent)”
Every quote above is checked against its source page before each update of this site; last checked 2026-10-06. The worked example is our own arithmetic. This page explains a term; it is not advice for a person's treatment.