Woman with CGM on arm for diabetes
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People with diabetes know that it is important to keep a close eye on their blood sugar levels.

Technology continues to evolve to help people with diabetes monitor their blood sugar levels so that they can keep them in their target range. Continuous glucose monitors (CGM) are one type of technology that provides that kind of vital information.

Since the 1990s, the diabetes community has relied on the hemoglobin A1C to evaluate average glucose levels over the course of 3 months.

The newer metric known as theglucose management indicator is helping some people with diabetes gain more insight into their blood sugars, and is helping them manage their diabetes better.

Monitoring your blood sugar levels is a key to living with diabetes.

High blood sugar levels can lead to potentially serious complications. Over time, high blood sugar levels can damage blood vessels that carry blood to your vital organs and lead to damage to your eyes, nerves, kidneys, and heart.

Very high blood sugar levels can also lead to a dangerous condition called diabetic ketoacidosis (DKA), which can lead to loss of consciousness, coma, or even death.

People used to compare their urine test results to a color-coded chart to monitor their blood sugar levels.

Home glucose meters became common in the 1980s. They used a fingerstick to check the blood on the test strip.

With the rise of continuous Glucose Monitoring technology, people with diabetes can now monitor their blood sugar levels more frequently and get a better idea of their diabetes management.

CGMs use a tiny sensor inserted under the top layer of skin. It measures the level of glucose in your interstitial fluid and transmits those readings every 1 to 5 minutes to a medical smartphone app or separate handheld device to see your glucose patterns in real-time.

It can help you keep your blood sugar levels within your target range.

You can see immediately when you have a big jump or drop in blood sugar, and you can determine what led to those big spikes and dips. Did you eat something that caused your blood sugar levels to go up? Did you exercise hard and cause your blood sugar levels to go down?

You no longer have to rely on fingerstick tests because of the advent of the CGM technology. You can get hundreds of blood sugar readings per day with the help of a CGM, since it takes about 5 minutes to read a blood sugar reading.

This technology has been a game-changer for many people with diabetes. Research shows that CGM tech helps those with diabetes (especially type 1 diabetes) better manage their condition and overall health.

People with diabetes have started using a measurement known as the GMI as the use of continuous positive meters has become more common.

The mean is the average of the data collected by your CGM. Here is how to get your GMI.

The GMI formula

You need the average glucose values from your CGM to get the GMI percentage:

The GMI is 3.31 + 0.02392.

If your meanglucose level was 150 sg/dL, your GMI would be 6.9%.

The A1C and the GMI are not the same.

Your A1C level reflects the average over the past 3 months, so you can take an A1C test whenever you want.

This kind of test is used to measure the amount of blood sugar in your red blood cells.

Why 3 months? The life span of a red blood cell is an average.

Typically, the higher your A1C, the higher your blood sugar levels you may have. For most people with diabetes, the recommended A1C level is 7% or below — although the specific number will vary and is best determined with your diabetes care team.

For many years, A1C was considered the go-to option for glycemic control. In fact, the landmark Diabetes Complications and Control Trial (DCCT) in 1993 established A1C as the gold standard.

“The A1C isn’t as reliable as once thought. The GMI was the better measurement in the late 2010s, as the #BeyondA1C movement took shape.”

Leading diabetes experts have determined that previous term “estimated A1C” (or eA1C) wasn’t helpful because people with diabetes might assume that it’s comparable to their 3-month A1C results.

Also, A1C does not reveal episodes of hypoglycemia or hyperglycemia, and research indicates that it can be skewed based on high or low blood sugars prior to an A1C lab test being performed.

In 2018, a team of researchers found that GMI was a better indicator of someone’s estimated glucose trends over time.

Although their study found that 51% of people only saw an approximate 3% difference between their GMI and laboratory A1C results, it’s still important to remember that they’re calculated differently. You’re using the mean glucose values from your CGM to determine the GMI rather than measuring how much sugar is attached to your red blood cells.

Your doctor will want to make sure you adjust your goals if your GMI is always lower than A1C. You might need to be more careful about how you manage the risk of hypoglycemic events.

The study suggested that if your GMI is always higher than your A1C, you should set your laboratory A1C target goal slightly lower to reduce the risk of excessive hyperglycemia.

One of the newer gold standards in diabetes management, particularly those who use CGM technology, is known as Time in Range (TIR). This is because TIR shows how often people are able to stay within the goalposts of their ideal range.

Your GMI can help you understand that.

When you use TIR, you get a better sense of how well you’re keeping your blood sugar levels in your target range. For most people, TIR should be about 70–180 mg/dL, and you want to aim to hit that range approximately 70% of the time. That’s about 17 hours out of a 24-hour day.

The less likely you are to develop problems the more you can keep your blood sugar in that range. You will reduce your risk of developing diseases like diabetes.

This table can help you understand more about GMI:

CGM-derived average glucose (mg/dL) GMI (%)
100 5.7
125 6.3
150 6.9
175 7.5
200 8.1
225 8.7
250 9.3
300 10.5
350 11.7

GMI numbers are not the same as A1C and should not be compared without first discussing the results with your diabetes care team.

“Any diabetes number, whether it is a singleglucose reading, a pattern on Time in Range, A1C result, or GMI measurement, is only a piece of information used in managing your diabetes. A result or number doesn’t define you.”

Essentially, you use the blood glucose levels from your CGM to come up with your GMI because the calculation uses the number from your mean glucose reading.

“There are some advantages to using a CGM. You don’t have to wait for 3 months to collect enough data to get a GMI.”

In fact, the The G6 is a type of toy. manufacturer advises you only need 12 days of CGM data to produce a GMI. A 2018 study found that you can get a good estimate of your CGM metrics over 3 months by using 10 to 14 days of CGM data.

The reading is more direct and accurate since you can calculate your GMI using blood sugar readings.

You need to have access to the tool to measure GMI. There are options if you are looking for a continuous glucose monitoring system. There are four different models available.

  • The G6 is a type of toy.
  • FreeStyle Libre 2 or 3 are available.
  • The Minimed Guardian connect.
  • Eversense is a device by Ascensia Diabetes Care.

You can talk to your diabetes care team about the best product for you.

You can use technology to keep track of your blood sugar levels.

The impact of choices you make and how well you keep your blood sugar levels in check can be learned with the help of the technology.

You can use both A1C and GMI to get the information you need to keep your blood sugar under control.