GMI on your Dexcom G7 stands for Glucose Management Indicator. It’s a percentage that estimates what your A1c would be based on your average sensor glucose readings. If you’ve seen a number like 6.8% or 7.2% in your Dexcom app and wondered what it means, that’s your GMI, and it gives you a running snapshot of your overall glucose control without needing a blood draw.
How GMI Is Calculated
GMI uses a straightforward formula that converts your average sensor glucose into an A1c-like percentage. The equation is: GMI (%) = 3.31 + 0.02392 × your mean glucose in mg/dL. So if your average glucose over the past 14 days was 154 mg/dL, your GMI would land around 7.0%.
The Dexcom G7 app will display your GMI once you’ve collected at least 7 days of sensor data. You can view it by opening the app, scrolling down to the “Clarity” card, and selecting a timeframe of 7, 14, 30, or 90 days. Your GMI appears just below your average glucose reading.
Why It’s Called GMI Instead of Estimated A1c
Before 2018, this metric was called “estimated A1c” or eA1c. The FDA raised concerns that labeling a CGM-derived number as an A1c estimate could confuse people into thinking it was identical to a lab-drawn A1c. In response, the metric was renamed to Glucose Management Indicator to make clear that it’s a related but distinct measurement. The name change was cosmetic. The underlying concept is the same: turning your sensor glucose average into a percentage you can compare against A1c targets.
How GMI Differs From a Lab A1c
Your GMI and your lab A1c can absolutely disagree, sometimes by half a percentage point or more. This doesn’t mean either number is wrong. They measure different things. A lab A1c reflects how much sugar has attached to your red blood cells over roughly two to three months. It’s a biological process influenced by how long your red blood cells live, whether you have anemia, kidney disease, or certain hemoglobin variants. GMI, on the other hand, is pure math applied to your sensor readings. It doesn’t care about red blood cell biology at all.
This means someone whose red blood cells turn over faster than average (common in pregnancy or iron-deficiency anemia) might have a lab A1c that reads lower than their GMI. The reverse can happen too. If your GMI consistently runs higher or lower than your lab results, that gap itself is useful information. It tells you and your care team how your body’s biology interacts with your actual glucose levels.
What a “Good” GMI Looks Like
The American Diabetes Association doesn’t set a standalone GMI target. Instead, GMI is treated as a stand-in for A1c when lab work isn’t available. For most nonpregnant adults with diabetes, the general A1c goal is below 7.0%, so a GMI below 7.0% roughly aligns with that.
That said, the ADA increasingly emphasizes Time in Range as the primary CGM metric. The recommended targets for most adults are spending more than 70% of the day between 70 and 180 mg/dL, less than 4% of the day below 70 mg/dL, and less than 1% below 54 mg/dL. GMI gives you a big-picture summary, but Time in Range tells you more about the day-to-day swings that affect how you feel and your long-term risk. The two metrics work best as a pair: GMI for the overview, Time in Range for the texture.
How to Use GMI Practically
Checking your GMI regularly on different timeframes can reveal trends that a single lab A1c misses. Looking at a 14-day GMI shows you the impact of recent changes, like a new meal pattern or exercise routine. The 90-day view gives you something closer to what a quarterly lab visit would capture. If your 14-day GMI has been trending downward while your 90-day number is still elevated, you know your recent adjustments are working even if the longer average hasn’t caught up yet.
One thing GMI won’t tell you is how variable your glucose is throughout the day. Two people can have an identical GMI of 7.0% while having very different daily experiences. One might hold steady between 130 and 170 mg/dL all day, while the other swings from 60 to 280. That’s why it helps to look at your GMI alongside your Time in Range and your glucose variability (listed as coefficient of variation in the Clarity reports, ideally 36% or lower).
If you notice your GMI and lab A1c are consistently more than 0.5 percentage points apart, mention it at your next appointment. The discrepancy can point to conditions affecting red blood cell turnover, or it can simply reflect normal biological variation. Either way, knowing the gap helps your care team interpret both numbers more accurately.