Glucose Sensors and Continuous Glucose Monitors (CGM)

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This article briefly summarizes continuous glucose monitoring (CGM) and refers you to additional pages for more information. Diabetes educators help patients who are considering CGM, or on CGM, by discussing expectations, product differences, interpretation of data and treatment decisions based on data. Without support from diabetes educators, patients using CGM may experience frustration and may make reactive insulin adjustments.

Continuous Glucose Monitoring: Quick Summary

Please also refer to the additional webpages listed in the CGM Topics segment above. 

  • CGM provides immediate access to glucose readings 24 hours a day with minimal fingerstick testing. CGM devices also display the speed and direction at which glucose levels are currently changing, as well as readings from past hours. Note that periodic fingerstick blood glucose testing is still required. 
  • Glucose sensors used in CGM technology measure interstitial glucose - glucose that has left the blood and moved into the tissues. Interstitial glucose levels are “older” than blood glucose levels by 5-15 minutes (or more if glucose levels are changing quickly). 
  • CGM provides numerous benefits to users which may include improved glycemic control. However, challenges are also present, with the most common being cost. 
  • In the past, CGM was primarily limited to those with type 1 diabetes or those on insulin pumps. However, current product indications now include use by those with type 2 diabetes.
  • Three brands of CGM are available in Canada -  Libre (Abbott), Dexcom and Medtronic (for use with Medtronic insulin pumps.) Each has unique features with different pricing.
  • CGM data can be viewed on handheld devices and additionally on online databases or computer downloaded software. CGM provides more data and different types of data than fingerstick blood glucose monitoring. Patients and healthcare providers must learn how to fully interpret this new and additional data. 
  • Most patients moving to CGM will make different insulin adjustment decisions based on the increased data, visual glucose trends and rate of change arrows. Diabetes educators can help patients decide on safe and impactful adjustments.
  • The value of CGM to help with diabetes management also depends on practices and patient preferences involving fingerstick glucose testing, calibration, alarms/alerts, sensor sites, skin care and troubleshooting.
  • Please view the additional pages in the coloured topics bar above.