GMI Calculator: Glucose Management Indicator
GMI (%) = 3.31 + 0.02392 × mean glucose (mg/dL). A mean of 154 mg/dL gives a GMI of about 7.0%. Paste readings below to get your mean, GMI and time in range, or type a mean you already have.
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Information only. Nothing you paste leaves your browser, and a result is not a diagnosis. Your care team may set different targets.
How it works
- Paste or type. Use readings from a meter or a CGM export, or a mean from your CGM report.
- We average and apply the published formula. Each reading is also sorted into the five bands used by the international consensus.
- You see where you stand. The table compares your shares with the consensus targets for most adults. Bring the result to your appointment, not a conclusion.
GMI (%): 3.31 + 0.02392 × mean glucose (mg/dL)
Bergenstal RM et al., Diabetes Care 2018;41:2275
Bands: below 54, 54 to 69, 70 to 180, 181 to 250, above 250 mg/dL
Battelino T et al. Clinical targets for CGM data interpretation: international consensus on time in range. Diabetes Care 2019;42:1593
2019 international time-in-range targets
An international panel of clinicians, researchers and people with diabetes agreed on CGM targets in 2019. The ADA lists the same numbers in its 2026 Standards of Care.
| Measure | Most adults (type 1 or type 2) | Older or high-risk adults (ADA: older adults with complex or intermediate health) |
|---|---|---|
| Time in range, 70 to 180 mg/dL (3.9 to 10.0 mmol/L) | more than 70% | more than 50% |
| Time below 70 mg/dL (3.9 mmol/L) | under 4% | under 1% |
| Time below 54 mg/dL (3.0 mmol/L) | under 1% | under 1% |
| Time above 180 mg/dL (10.0 mmol/L) | under 25% | under 50% |
| Time above 250 mg/dL (13.9 mmol/L) | under 5% | under 10% |
Pregnancy has its own, tighter targets set by the care team. The ADA gives no standard goal for GMI or mean glucose. The consensus asks for at least 14 days of data with the sensor worn 70% of the time to judge these numbers.
What GMI is, and what it is not
A lab A1C measures the share of hemoglobin with sugar attached, which tracks average glucose over about three months. A CGM measures glucose directly every few minutes. In 2018 researchers compared CGM averages with lab A1C in several large studies and published an equation that turns a CGM mean into an A1C-like number. That number is GMI.
The two often disagree by a few tenths of a percent because they measure different things over different periods. A GMI higher or lower than your A1C is not an error. It can reflect how long your red blood cells live, certain hemoglobin variants, anemia, kidney disease or just a different two weeks. If they differ a lot, ask your clinician which to trust for your decisions. See the A1C calculator for the lab-A1C side of the same idea.
Why time in range matters beside GMI
A mean can hide the shape of a day. Two people can share a mean of 154 mg/dL while one sits steadily near it and the other swings between 50 and 300. Time in range, time below range and variability show the swings that an average smooths away. That is why the ADA lists them next to A1C. Lows matter most: any share of readings under 54 mg/dL is worth raising with your care team, and the low blood sugar symptoms page lists what to watch for.
Frequently asked questions
What does GMI stand for?
Glucose management indicator. It is a number, shown as a percentage like an A1C, calculated from the average glucose a continuous glucose monitor (CGM) recorded. The formula is GMI (%) = 3.31 + 0.02392 × mean glucose in mg/dL.
Is GMI the same as A1C?
No. A1C is a lab test of hemoglobin. GMI is calculated from CGM readings, usually over 14 days. The two often differ by a few tenths of a percent, and sometimes by more. The ADA calls GMI a value approximating A1C that is not always equivalent.
Why is my GMI different from my A1C?
A1C reflects about three months and can be shifted by how long your red blood cells live, by anemia, kidney disease, pregnancy and some hemoglobin variants. GMI reflects only the days the sensor was worn. Ask your clinician to look at both.
Can I get GMI from finger-stick readings?
You can plug them in, but GMI was built on CGM data that covers the whole day and night. A few finger sticks often miss overnight and after-meal values, so the result is rough. This tool says so when you paste fewer than 14 readings.
What are the 2019 international time-in-range targets?
For most adults with type 1 or type 2 diabetes: more than 70% of readings between 70 and 180 mg/dL, under 4% below 70, under 1% below 54, under 25% above 180 and under 5% above 250. The ADA Standards of Care 2026 list the same targets. Older or high-risk adults have different ones.
Information only, not medical advice. Your care team may set different targets for you, and only a lab test ordered by a clinician can diagnose diabetes or prediabetes. See our medical disclaimer.
Sources
- Bergenstal RM et al. Glucose Management Indicator (GMI). Diabetes Care 2018;41:2275
- Battelino T et al. Clinical targets for CGM data interpretation: international consensus on time in range. Diabetes Care 2019;42:1593
- ADA Standards of Care in Diabetes—2026, Section 6: Glycemic Goals, Hypoglycemia, and Hyperglycemic Crises
- ADA Standards of Care in Diabetes—2026, Section 2: Diagnosis and Classification
Last reviewed: by the Diabetes Blogs editorial team. Information only, not medical advice.
