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Continuous Glucose Monitoring

Topic Overview

When you test your blood sugar (glucose), you learn your blood sugar level at that time. But you can't tell what's happening to your blood sugar the rest of the time—especially overnight. A continuous glucose monitor (CGM) or Flash Glucose Monitor (Flash), can do that for you.

How does a continuous glucose monitor or flash glucose monitor work?

A CGM has several parts. You wear one part—the sensor—against your skin. It has a tiny needle that stays under your skin. The sensor is constantly reading your sugar level of the fluid between your cells (interstitial). The sensor sends this information to the other part of the monitor, a wireless receiver. Some insulin pumps include CGM. In this case, the insulin pump is also the receiver.

A Flash also has several parts. You wear one part—the sensor—against your skin. It has a tiny needle that stays under your skin. The other part is a wireless reader device that displays your glucose level when the sensor is “flashed” with the reader device. You can get a reading when you need it (on demand).

There can be a 5 to 15 minute difference between an interstitial sugar level and a blood sugar level. If your sugar levels are not changing quickly, like after eating a meal, there will be little difference between your interstitial sugar level and your blood sugar level.

At any time, you can look at the receiver and see what your sugar level is. Some systems use text messages, apps, and websites. You can see if your level is going up or down—and how fast. You can see the trends and patterns of your glucose levels.

You note on the receiver when you eat, do exercise, and take insulin. That way you can see how those activities affect your sugar levels throughout the day and night.

All this detailed information gives you and your diabetes care-team a better idea of what your treatment needs are.

Some CGM and Flash monitors need you to prick your finger and use your standard blood glucose meter to confirm what the monitor is telling you.

What are the benefits?

A CGM or Flash is constantly measuring your sugar levels. This information helps some people who have diabetes make decisions about what to eat, how to exercise, and how much medicine to take.

Some CGMs have an alarm feature to alert you if your sugar level is quickly going up or down, or if you have a sugar level out of your target range. This is helpful for people who have problems knowing when they have low blood sugar (hypoglycemic unawareness). Parents, partners, or caregivers can be alerted when the sugar level is dropping quickly while you are asleep.

What are the drawbacks?

  • Sensors need to be changed. Depending on the system, you may need to change the sensor every few days. Some systems have sensors that last 10-14 days.
  • Some CGMs will require that you prick your finger to confirm the CGM's accuracy.
  • Acetaminophen (Tylenol) and other medicines can affect the results in some CGMs, reporting the readings higher or lower than they actually are.
  • If you are sick, dehydrated, or if the sensor is not inserted properly the results in some CGMs, may report the readings higher or lower than they actually are.
  • If you are interested in using a CGM or Flash you should talk with your diabetes care team for more information.

References

Other Works Consulted

  • Juvenile Diabetes Research Foundation Continuous Glucose Monitoring Study Group (2008). Continuous glucose monitoring and intensive treatment of type 1 diabetes. JAMA, 359: 1–13.
  • Juvenile Diabetes Research Foundation Continuous Glucose Monitoring Study Group (2009). The effect of continuous glucose monitoring in well-controlled type 1 diabetes. Diabetes Care, 32(8): 1378–1383.

Credits

Adaptation Date: 9/15/2021

Adapted By: Alberta Health Services

Adaptation Reviewed By: Alberta Health Services

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