People with diabetes quickly learn that it is essential to monitor their blood sugar closely.
Technology continues to evolve to help people with diabetes monitor their blood sugar so they can keep it within their target range. Continuous glucose monitors (CGMs) are one type of technology that provides this type of vital information.
Since the 1990s, the diabetes community has relied on hemoglobin A1C to assess average glucose levels over a 3-month period.
But with modern CGM technology, a new measurement known as the Glucose Management Indicator (GMI) is helping some people with diabetes better understand their glucose fluctuations and helping them better manage their diabetes.
The key to living with diabetes is monitoring your blood sugar (glucose) levels.
High blood sugar can lead to potentially serious complications. Over time, high blood sugar can damage the blood vessels that carry blood to your vital organs and damage your eyes, nerves, kidneys and heart.
Very high blood sugar can also lead to a dangerous condition called diabetic ketoacidosis (DKA), which can lead to loss of consciousness, coma, or even death.
In the beginning, people monitored their blood sugar by placing a test strip in their urine and comparing it to a color-coded chart.
Then, in the 1980s, home glucometers became common. They used a finger to check for a drop of blood on another type of test strip.
But with the rise of CGM technology in the early 2000s, people with diabetes can now more continuously monitor their blood sugar levels and get a more complete picture of trends in their diabetes management.
CGMs use a tiny sensor inserted under the top layer of skin. It measures the level of glucose in your
This information can help you make adjustments throughout the day to keep your blood sugar within your target range.
You can see immediately when you experience a big jump or dip in blood sugar, and you can determine what led to those big spikes and dips. Did you eat something that raised your blood sugar? Or did you exercise hard and cause your blood sugar to drop?
The advent of CGM technology means you no longer have to rely on routine testing at your fingertips. And since CGMs can take a reading every 5 minutes or so and send the data to your smartphone or tablet, you can get hundreds of blood glucose readings per day.
This technology has been a game changer for many people with diabetes.
As CGM became more common, people with diabetes began using a measurement known as GMI.
Your GMI is the mean (average) glucose value based on data collected by your CGM. Here’s how to get your GMI.
The GMI is not the same as the A1C.
An A1C test measures your blood sugar over the past 3 months, so your A1C level reflects the average over that long period.
Specifically, this type of test measures the amount of blood sugar, or blood sugar, attached to hemoglobin in your red blood cells.
Why 3 months? This is the average lifespan of a red blood cell.
Generally, the higher your A1C, the higher your blood sugar can be. For most people with diabetes, the recommended A1C level is
For many years, A1C was considered the go-to option for blood sugar control. In fact, the landmark
However, advances in diabetes technology have revealed that A1C is not as reliable as previously thought. The #BeyondA1C movement took shape in the second half of the 2010s, and the GMI was recognized as the best measure.
Leading diabetes experts have determined that the previous term “estimated A1C” (or eA1C) was not useful because people with diabetes could
In addition, A1C does not reveal hypoglycemic or hyperglycemic episodes, and to research indicates that it may be biased based on high or low blood sugar before an A1C lab test is performed.
In 2018, a team of researchers found that the GMI was a better indicator of a person’s estimated blood sugar trends over time.
Although their study found that 51% of people saw only about a 3% difference between their GMI and A1C lab results, it’s always important to remember that they are calculated differently. You are using the average glucose values from your CGM to determine the GMI rather than measuring the amount of sugar attached to your red blood cells.
If your GMI is still lower than your A1C, your doctor will want to make sure you adjust your target goals accordingly. You may also need to be more vigilant to minimize the risk of low blood sugar.
The study suggested that if your GMI is still higher than your A1C, you should set your target lab A1C goal slightly lower to reduce the risk of excessive hyperglycemia.
One of the new benchmarks in diabetes management, especially for those using CGM technology, is known as Time in Range (TIR). Indeed, the TIR shows how often people are able to stay within their ideal range.
Your GMI can help you figure this out.
When you use TIR, you get a better idea of how well you are keeping your blood sugar within your target range. For most people, the TIR should be around 70–180mg/dLand you want to reach this range approximately 70% time. It’s about 17 hours over a 24-hour day.
This is important because the longer you can keep your blood sugar within this range, the less likely you are to develop complications. You will reduce your risk of developing conditions such as diabetic retinopathy or kidney disease.
This table can help you learn more about GMI:
Remember, however, that GMI numbers are not the same as A1C numbers and should not be compared without first discussing the results with your endocrinologist or diabetes care team.
More importantly, any diabetes number – whether it’s a single glucose reading, a time-in-range pattern, an A1C result, or a GMI measurement – is only a piece of information used in the management of your diabetes. A number or result does not define you.
Essentially, you use your CGM blood sugar levels to determine your GMI because the calculation uses the number from your average glucose reading.
And there are a few key advantages to using a CGM to obtain GMI data. For one, you don’t have to wait 3 months to collect enough data to get a GMI.
In fact, the manufacturer of the Dexcom G6 advises that you only need 12 days of CGM data to produce a GMI. A
Since you can calculate your GMI using blood glucose readings over a shorter time frame, the reading is more accurate and direct.
You must have access to the CGM to be able to measure your GMI. If you’re looking for a continuous blood glucose monitoring system, the choice is yours. Four different models are available from 2022:
- Dexcom G6
- FreeStyle Libre 2 or 3
- Medtronic Minimed Guardian Connect.
- Eversense Implantable CGM by Ascensia Diabetes Care
You can discuss with your endocrinologist or diabetes care team which type of product might be your best option.
Thanks to advancements in technology, you now have more options to help you track your blood sugar.
CGM technology can help you learn more about your blood sugar, including the immediate impact of the choices you make and how well you keep your blood sugar within your target range over time.
Using both A1C and GMI gives you the information you need to better control your blood sugar and stay as healthy as possible.