What Are Continuous Glucose Monitoring Products?

by Jessica Pyhtila, PharmD, BCPS, BCGP

When you have diabetes, it can be painful to undergo constant finger-sticks to check your blood sugar. To avoid the need for regular finger-sticks in both those with Type 1 and Type 2 diabetes, several companies have developed continuous glucose monitoring (CGM) products. If you are looking for a way to control your blood sugar while minimizing the need for finger-sticks, a CGM may be an option.

When Are CGMs Used?

CGMs are used when it is useful to have a close-to-real time measurement of your blood sugar. Most CGMs will check your blood sugar once every 5 minutes, or approximately 288 times per day. They are often used in people whose blood sugars may fluctuate due to:

  • Unexpected hypoglycemic (low blood sugar) events
  • Irregular food intake
  • Medications that impact blood sugar levels
  • Stress
  • Physical activity

The regular checking of your blood sugar once every few minutes can help your doctor track trends in your blood sugar, including overnight. This can help your doctor optimize your diabetes medications. It can also help you predict and prevent low blood sugar episodes linked with skipping meals or increased physical activity.

Does Insurance Cover CGMs?

Your insurance may cover a CGM, depending on your medical history. In the past, Medicare coverage for CGMs was limited to those on insulin who had to check their blood sugar four times a day or more. However, this requirement was loosened as of July 2021. Now, anyone on insulin may qualify for a CGM covered by Medicare if their doctor believes it would benefit them.

What Benefits Do CGMs Have Over Traditional Finger-Sticks?

CGMs have multiple advantages over traditional finger-sticks, including:

  • Immediate notification about blood sugar levels: CGMs allow you to set alerts when your blood sugar is over or under a certain level, allowing you to treat your blood sugar quickly
  • Informing you about trends: Your CGM can tell you how quickly your blood sugar is increasing or decreasing and can link it to events like food intake or exercise so you can better predict your blood sugar changes. You can examine these trends both in real-time, and after the fact with your doctor. Some CGMs can even predict future episodes of high or low blood sugar, and can inform you about them ahead of time so they can be prevented.
  • Remote monitoring: Because CGM results are often uploaded into a central database remotely, your doctor may be able to examine your blood sugar readings even between appointments.

What Supplies Do CGMs Require?

CGMs measure the blood sugar in the interstitial fluid of your cells, meaning the fluid surrounding your cells’ tissues. As such, they require supplies to help measure this particular type of fluid. Although CGMs vary, they typically require similar supplies like:

  • A sensor: The CGM sensor is the part of the device that comes into contact with your blood sugar. It then relays the information to the CGM device via a transmitter. The sensor needs to be replaced every 7 through 90 days, depending on the CGM.
  • A receiver: The CGM receiver is the part of the device that obtains the sensor’s blood sugar readings. The receiver may be a standalone device, may be incorporated into an insulin pump, or may be an app on your smartphone.

What CGMs Are Available in the United States?

Several different CGM brands are available in the United States. Although they have aspects in common, they have individual features that may make them more appropriate for one person versus another. For example, a person who uses an insulin pump may benefit more from a CGM that integrates with the pump than a stand-alone CGM.

Available CGM products include:

  Freestyle Libre Dexcom G6 Medtronic Guardian Senseonics Eversense
Calibration required? No No Yes, calibration is needed every 12 hours. Blood sugar must be between 40 and 400 mg/dl to successfully calibrate. No
Sensor Duration 14 days 10 days 7 days 90 days
Location of sensor Back of arm Back of arm, abdomen, upper buttocks Back of arm, abdomen Back of arm
How blood sugar levels are displayed Number values and trends Number values and trends Number values and trends Number values and trends
Alarms Low sugar, high sugar, and signal loss Low sugar, high sugar, rapid rise or fall in sugar, customizable alarms Low sugar, high sugar, rapid rise or fall in sugar, predictive upcoming high or low blood sugar, calibration required, connection/signal problems, customizable alarms Low sugar, high sugar, predictive upcoming high or low blood sugar
Transmitter range required for sensor to be scanned 1.5 inches 20 feet 20 feet 25 feet
Warm-Up Time 1 hour 2 hours 2 hours 24 hours
Age range Age 4 and up for Abbott FreeStyle Libre 2   Age 18 and up for FreeStyle Libre 14-Day System Age 2 and up Age 2 and up for Guardian Sensor 3   Age 14 and up for Guardian Connect CGM System Age 18 and up
Software supported for remote monitoring Windows, Mac/iOS, and cloud-based LibreView Dexcom CLARITY, iOS, Android Windows, Mac, MiniMed Mobile app and web-based CareLink Eversense app
Integrates with insulin pump? No No Yes, the Guardian Sensor 3 integrates with the MiniMed 770G and MiniMed 630G insulin pumps No
Receiver required to read the sensor? Yes Yes Yes for the Guardian Sensor 3   No for the Guardian Connect CGM System No

CGM technology has continued to evolve over the past several years, and now incorporates apps as well as cloud-based data storage. In addition, insurance coverage for CGMs has broadened, with increased Medicare coverage for CGMs being a recent win. Your doctor can help you decide whether a CGM may be helpful to you as you manage your diabetes.


American Diabetes Association. “CGMs.” n.d. Retrieved from https://consumerguide.diabetes.org/collections/cgm

American Diabetes Association. “Abbott FreeStyle Libre 2.” n.d. Retrieved from https://consumerguide.diabetes.org/collections/cgm/products/abbott-freestyle-libre-2

American Diabetes Association. “FreeStyle Libre 14-Day System.” n.d. Retrieved from https://consumerguide.diabetes.org/collections/cgm/products/freestyle-libre-14-day-system

Dexcom. “Where can I insert my G6 sensor?” n.d. Retrieved from https://www.dexcom.com/en-GB/faq/where-can-i-insert-my-g6-sensor

American Diabetes Association. “G6 CGM System.” n.d. Retrieved from https://consumerguide.diabetes.org/collections/cgm/products/g6-cgm-system

Medtronic. “Inserting and Starting the Sensor.” n.d. Retrieved from https://www.medtronicdiabetes.com/customer-support/guardian-connect-system-support/inserting-and-starting-sensor

American Diabetes Association. “Guardian Sensor 3.” n.d. Retrieved from https://consumerguide.diabetes.org/collections/cgm/products/guardian-sensor-3

American Diabetes Association. “Guardian Connect CGM System.” n.d. Retrieved from https://consumerguide.diabetes.org/collections/cgm/products/guardian-connect-cgm-system

American Diabetes Association. “Eversense CGM System.” n.d. Retrieved from https://consumerguide.diabetes.org/collections/cgm/products/eversense-cgm-system

Food and Drug Administration. “Eversense CGM Sensor Insertion and Removal Instructions.” n.d. Retrieved from https://www.fda.gov/media/112159/download

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