Continuous Glucose Monitoring Systems

A Continuous Glucose Monitor is a small device worn under the skin that uses interstitial fluid to monitor blood glucose levels. It then transmits readings to a receiver and allows a person with diabetes to have a guide to what blood glucose levels may be at a given time and whether they are expected to rise or fall in the near future.

What is the difference between traditional glucose testing and using a Continuous Glucose Monitor?

glucometer or cgm

Glucometers are portable devices that read glucose levels from a blood sample that is placed on a tiny test strip. Test strips are discarded after a single-use.  Some meters store a limited number of glucose results in memory. The results can be downloaded into a computer.

glucose sensor, on the other hand, is a tiny electrode that is inserted under a patient’s skin (subcutaneous tissue) that continuously records glucose levels around the clock. The sensor is worn for between three to seven days before it is discarded and replaced by the patient.  Glucose readings are transmitted to a monitor, smartphone or insulin pump where the values are displayed. Trend reports and charts can be viewed after data is downloaded to a computer.

Download our free CGM/Flash monitoring systems comparison sheet.

Types of Continuous Glucose Monitors

Dexcom G5
Dexcom G5®

The Dexcom G5® shows where your blood glucose is, where it’s going, and how fast it’s getting there. This Continous Glucose Monitor only requires calibration every 12 hours (if you feel that the CGM reading is off, always refer back to your glucometer reading however).

The Dexcom G5® Mobile is approved for adults and children 2 years and older.

It uses Bluetooth technology to send information from the transmitter to your Andriod or Apple mobile device. It provides real-time glucose values that can be used to make treatment decisions. Text messages and alerts for highs and lows can be sent to your device as well as can be shared with loved ones for added protection.

Transmitters are warranted for 3 months from the time they are shipped. Sensors are to be changed out after 7 days.

Dexcom G6
 Dexcom G6®

The Dexcom G6® is the most updated version of the Dexcom® CGM.  This product also uses Bluetooth technology but now has sensors that last 10 days. This sensor is water-resistant. It no longer requires calibration but users can still choose to enter a calibration if they would like to or feel that the sensor seems inaccurate. The Dexcom G6® still requires a 2-hour warm-up period. The “urgent low soon” alarm will alert the user when blood glucose is dropping rapidly and is expected to cross the low threshold. It also has a new easy-to-use, push-button applicator that is said to be less painful than the G5 insertion. The sensor will last for 10 days and will no longer be bothered by acetaminophen use.

It continues to work with smartphones, as a standalone device, and with the latest US version of the Tandem insulin pump.


Medtronic 630G
Enlite™ glucose sensor and MiniLink™ transmitter

This CGM system also offers real-time glucose monitoring. It wirelessly sends glucose readings to the insulin pump every 5 minutes. Sensors should be changed every 6 days and calibrated twice per day.

Flash Monitoring Systems

Flash monitoring systems do not continuously transmit readings to a monitor, smart device or insulin pump. Readings are transmitted when the system reader is passed over the receiver.

The Libre Flash Monitoring system is convenient and discreet. It requires no calibration. With each scan you get the current glucose reading, the last 8 hours of glucose data and an arrow showing the direction glucose readings are heading. These sensors are also safe to wear in the pool or shower.

Libre does not currently work with any insulin pump but talks are ongoing with Tandem Diabetes Care to change this.

Eversense® Continuous Glucose Monitor System

eversense cgm

Eversense® provides continuous blood glucose monitoring for up to 90 days via an under-the-skin sensor, a removable and rechargeable smart transmitter, and an app for real-time diabetes monitoring and management. You will receive real-time glucose measurements on your mobile phone or smartwatch. There is no separate receiver required.

The sensor must be implanted by a medical professional.

This system is currently only available in the US.

How to decide if a CGM or Flash system is right for you

continuous glucose monitors

Deciding which system you should use or even if you want to be hooked up to a device at all is a very personal decision. You may want to consider things like

  • Cost
  • Sensor size
  • Life of a sensor
  • Number of times you have to calibrate the system
  • Can you share your data with others

For more things to consider when thinking about a Continuous Glucose Monitor or Flash Monitoring system, read our blog post
Is a Continuous Glucose or Flash Monitor Right for You?

Studies on the effectiveness of Continous Glucose and Flash Monitoring Systems

Comparison of Two Continuous Glucose Monitoring Systems, Dexcom G4 Platinum and Medtronic Paradigm Veo Enlite System, at Rest and During Exercise, June 2106  

18 month comparison of Medtronic Enlite and Dexcom4