What is GMI and Why is it Important?
Oct. 14 2021
Glucose Management Indicator (GMI) is what your approximate A1C level is likely to be.
According to Dexcom, “Glucose Management Indicator (GMI) approximates the laboratory A1C level expected based on average glucose measured using continuous glucose monitoring (CGM) values. Average glucose is derived from at least 12 days of CGM data. The GMI may be similar to, higher than, or lower than the laboratory A1C. Differences between GMI and laboratory A1C may reflect differences among an individual’s red blood cell lifespan, how glucose binds to hemoglobin, or due to a recent fluctuation in glucose control.” It used to be known as estimated A1C (or eA1C) but was changed to “GMI” for clarity.
However, if you wear a Continuous Glucose Monitor (CGM) like most Level2 members, it makes sense to also measure GMI. GMI is calculated from your average CGM glucose, which measures glucose in the interstitial fluid (under the skin) every 1 to 5 minutes. The CGM offers a large amount of data as well as the ability to account for glucose spikes and falls, and GMI offers an opportunity to make sense of that data. (It’s particularly important to pay attention to your time in range, or TIR, which is also a metric that is important to CGM wearers.)
Differences in GMI and A1C
There may be differences between the numbers you see in your GMI and A1C reports. This is nothing to feel alarmed about. GMI and A1C are measuring two different things.
What does A1C tell you?
Most people with type 2 diabetes know about A1C and what that number means, but as a quick refresher: You can learn A1C from a simple blood test that can give a picture of your average blood sugar level over the past two to three months. The higher the levels, the greater your risk of developing diabetes complications. Your health provider will tell you how often you need the A1C test, but it is typically done at least twice a year if you’re meeting your treatment goals. If you are not meeting your goals or you change treatments, you may need to get an A1C test more often. (Learn more here.)
What does GMI tell you?
GMI approximates the laboratory A1C level expected based on average glucose measured using continuous glucose monitoring (CGM) values. Average glucose is derived from at least 12 days of CGM data. GMI is calculated from the direct measure of glucose in interstitial fluid, which is the fluid between cells.
Other Reasons for Differences in Metrics
A1C is slower to change and measured over two to three months versus 10-14 days for GMI. So the timeframes of measurement are not the same either. GMI is able to assess short to intermediate average giving better feedback to recent changes in glucose.
Finally, your A1C numbers can be affected by a number of other factors including the presence of liver or kidney disease, pregnancy, a person’s ethnic background and more. Level2 believes both GMI and A1C are important metrics in understanding how you can work to achieve remission. The bottom line? Continue to check your GMI in your Weekly Member Insights email, and don’t skip your doctors’ appointments.
Level2 members can learn their GMI from the Level2 Weekly Member Insights report and should feel free to discuss it with their Level2 care team or diabetes care provider.