Continuous Glucose Monitoring System (CGMS)

A CGM system is a device that you wear to measure glucose levels in real-time, day and night — even during sleep it's watching out for you. This is like seeing up to 288 finger sticks daily, but unlike finger sticks, you see so much more than just a number. You see continuous glucose information, the direction your glucose is headed, and the speed it's moving.

Continuous glucose monitoring systems (CGMS) use a tiny sensor wire called a glucose sensor inserted under the skin (subcutaneous) to measure glucose levels in the fluid in the body’s fat tissue. This is also known as interstitial fluid. It is connected to a transmitter that sends the information wirelessly to a display device. In some cases, the information is sent directly to a smart phone.  

A continuous glucose monitoring system helps to:

  • Track trends and patterns in glucose levels over time.
  • Prevent hypoglycemia.
  • Have a better understanding of what happens to blood glucose during and after exercise.
  • See how foods affect the blood glucose (for example-rapid rise or delayed high).
  • Better understand what happens to blood glucose overnight while sleeping.
  • Decrease finger sticks.
  • Improve overall blood glucose control.

Frequently asked questions:

What is the difference between a CGMS and a glucometer?

CGMS read and display interstitial fluid glucose, Glucometers read blood glucose. Therefore, your sensor glucose and your blood glucose readings may not always be the same.

What is lag time?

Glucose travels to the bloodstream first and then enters the interstitial fluid. There is about a 15-minute delay in the sensor glucose from the finger-stick blood glucose reading. We refer to this as lag time.

What are calibrations?

Calibrations are blood glucose readings taken on a glucometer and manually entered into the CGMS. Timely calibrations keep your sensor accurate. Device manufacturers provide guidelines for calibration times and frequency.

For the best results:

  • Use good finger-stick technique.
  • Enter the blood glucose reading into the receiver within 5 minutes of sampling.
  • Calibrate when glucose levels are relatively stable to avoid discrepancies related to lag time.
  • Know if your device is factory calibrated. It may only require calibration if the finger-stick is significantly different from sensor value.

Will insurance pay for CGMS?

Most insurance companies are paying for CGMS.

What about alarms and alerts?

CGMS will be most helpful if the alerts and alarms are set to help improve blood glucose control. Alarms and alerts can be personalized:

  • High and Low Glucose Alerts
  • Predictive Alerts
  • Rate of Change Alerts
  • Calibration Alerts
  • Out of Range Alert

How can the CGMS data or information be viewed?

CGMS data can be viewed on a receiver, an insulin pump screen, or a mobile device (smart phone). Data on devices can be uploaded to a computer using company-specific software or web-based programs that contain various graphs and data tables. Data can also be viewed through cloud-based technology. Data can be shared with followers in real time.

How can CGMS improve diabetes control?

It is important to establish realistic expectations before using CGMS. CGMS-generated glucose values are estimates. The true value of CGMS comes from the high/low alerts, trending information, and data analysis that can be performed after wearing the sensor over time.

What CGMS are available?

There are several CGM systems available for pediatric use. Examples include:

Work with your diabetes team to decide which device is right for you.

This information should not be considered medical advice, nor is it intended to replace consultation with a qualified physician or other qualified healthcare provider. The Diabetes Center for Children does not evaluate, endorse or recommend any particular product or manufacturer. If you have questions about your health, please contact your healthcare provider.