There are two main types of CGM devices: real-time and intermittently scanned.
Real-Time CGMs
There are three main components to real-time CGMs.
- Sensor: This is a small wire catheter inserted under the skin, usually on an arm or abdomen. The sensor typically monitors real-time glucose levels every five minutes. Depending on the system, it is usually worn for 7–14 days. (An exception is the Eversense Implantable CGM, which can be worn for up to 90 days.)
- Transmitter: This is attached to the sensor and sends glucose information to a receiver or Smartphone app. Most systems have a transmitter that can be used for up to 12 months. However, some systems, such as the FreeStyle Libre, have no reusable transmitter since each sensor is fully disposed of after 14 days, and a new one is inserted.
- Handheld receiver and/or smartphone app: These receive the real-time glucose level and display the glucose data in real-time. Most CGMs offer smartphone apps for obtaining data and displaying real-time glucose and glucose level trends and history. (Some CGM devices also send glucose values to an insulin pump, allowing for automatic delivery of insulin according to glucose level data.)
Pros:
- The most significant benefit of real-time CGM systems is the ability to have audible alarms to warn an individual if their blood glucose level is too high. This allows for adjustments to decrease the impact of a high or low blood glucose level.
- Many real-time CGMs eliminate finger sticks, allowing treatment decisions to be made without the need for finger-stick confirmation of glucose levels.
- Real-time CGMs transmit data continuously to a receiver or smartphone without additional action.
- There is the ability to share data with family and friends.
Cons:
- To use the alarm and alert features, an individual must program the settings for glucose threshold and target ranges, which can become somewhat complicated for some individuals.
- Alerts can be somewhat bothersome for some people because of the repeated alarms, both real and false.
- Devices can be costly, especially if an individual has to pay out of pocket. However, Medicare and many insurers cover the costs.
