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FreeStyle Libre: a Continuous Glucose Monitoring Systems

Continuous Glucose Monitoring Systems: Everything You Need to Know

Jason Collier - 5th Sept 2018 [updated 16th Sep 2019] - Diabetes / Medical Device

Continuous glucose monitoring (CGM) systems provide continuous insight into your glucose levels – throughout the day and at night! They have the potential to be lifesaving devices to all types of diabetics by alerting the user before he or she starts to experience high or low blood glucose levels.

CGM helps eliminate the guesswork that comes from making decisions based solely on a number from a blood glucose meter reading using handheld glucose meters. This will result in better diabetes management.

You may be interested in CGM, but you want to find out how it works, what the benefits are, if the system will work for you, what CGM systems are available and what the costs involved are. Well, look no further!

How Does Continuous Glucose Monitoring (CGM) Work?

As the name suggests, CGM systems monitor your glucose levels continuously throughout the day. The system usually consists of three components: a sensor, a transmitter and a receiver

The sensor is inserted subcutaneously (under the skin), which measures the glucose levels in the interstitial fluid. It is placed on the abdomen or at the back of the upper arm. Each sensor has a maximum lifespan of 7-14 days before it needs to be replaced. The sensors measure glucose levels once every 1-5 minutes and require calibration from a handheld glucose meter daily. The values may vary depending on the brand used.

The data is transmitted from the sensor, via a connected transmitter, to a receiver which can store or display the info. The transmitter is adhered to the skin’s surface and has a wired connection to the sensor.

Dexcom G6® CGM

Source: FreeStyle Libre

In these modern times, the systems are integrated with smartphones, which function as the receiver, displaying your glucose levels numerically and graphically, in real-time! This means that trends like the direction and speed of the changing glucose levels can be analysed. Alerts can also be programmed to alert patients and caregivers of possible glucose highs or lows.

The data can also be transmitted to an insulin pump for a closed-loop circuit, like Medtronic’s MiniMed™ 670G system. The insulin pump will automatically vary the amount of insulin it releases into the body based on the continuous glucose data it receives.

What CGM Systems Are on the Market?

The most well-known CGM systems currently on the market are the Dexcom G6® CGM (seen in the image below), the Medtronic’s Guardian™ Connect CGM, the FreeStyle Libre system and the Eversense® CGM System.

Dexcom G6 Suite

Source: Dexcom

Each of the different systems have their own set of pros and cons. For example, The Eversense® CGM System comes with a sensor which lasts 3 months! However, it must be implanted by a physician in a relatively simple procedure. The other sensors used in the other systems have a lifetime of 7-14 weeks and can be inserted without the help of a physician.

The Eversense® CGM System is the only system which works even when the transmitter is not attached. The FreeStyle Libre doesn’t use a transmitter – it just has a reader and a sensor!

All of the systems, except for the FreeStyle Libre System, have the ability to transfer data to smartphones. However, all of the systems come with a dedicated display device (receiver) and software to analyse blood glucose trends long term.

All of the systems alert the user when glucose levels are too low or too high. The Dexcom G6® CGM and Guardian™ Connect CGM go one step further with smart alerts. These predictive alerts notify the user of oncoming lows and highs in glucose levels so that the user can make the necessary intervention

All of the systems are water resistant. This allows you to bath, shower, swim and live your active lifestyle without worrying about your CGM system.

The sensors and transmitters are placed either on the abdomen or on the back of the upper arm. Dexcom G6® CGM and Guardian™ Connect CGM are also suitable for children!

What Are the Benefits of CGM?

The benefits of mobile health (mHealth) used to aid the self-management of diabetes are well documented. However, CGM brings a new dimension to diabetes self-management when compared to using handheld glucose meters with testing strips. Here are some of the main benefits:

  • CGM systems provide you with real-time data, showing your current glucose levels and how your glucose levels are trending.
  • These devices alert you when your glucose levels are too high or too low.
  • They minimise the need for you to use handheld glucose meters with testing strips.
  • CGM systems can connect to insulin pumps which automatically deliver insulin.
  • They can monitor glucose levels at night and alert you if your levels are too high or too low.
  • Parents can monitor their children remotely and can let the system monitor their children at night.
  • CGM systems provide insights into how food, physical activity, medication and illness impacts your diabetes.


Source: Dexcom

However, it must be noted that CGM systems are costly – some more so than others. The sensors are especially costly as they are disposable and need to be replaced periodically. More and more insurers are providing coverage for CGM systems, but there will always be situations where the cost will be a determinant for the specific CGM device recommended. There are always going to be issues with mobile health. Some issues specific to CGM systems include:

  • potential skin reactions to the sensor or adhesives,
  • inadvertent sensor detachment, and
  • loss of sensor data signal.

Frequently Asked Questions (FAQ)

Who should use a CGM system?

CGM systems can benefit those diagnosed with type 1 diabetes, type 2 diabetes and even gestational diabetes! Other reasons to consider using CGM can be that:

  • You are not meeting your HbA1c goals and your doctor cannot get your glucose levels under control.
  • You display gestational diabetes risk factors and want to monitor your glucose levels during your pregnancy.
  • You have an insulin pump and want to connect it to a CGM system for a closed-loop circuit.
  • You want to monitor your diabetic child closely.
  • You get annoyed testing your glucose levels with handheld glucose meters and test strips so often.
What activities can one do while using a CGM?

CGM systems are designed to allow you to live an active life without intruding. This means that you can run, swim and travel with no worries. However, there are some factors to consider when living with a CGM system:

  • Airport officials around the world are generally familiar with CGM systems, but it is important not to put them through x-ray machines.
  • This goes for any other type of imaging systems which may be performed at hospitals too.
  • Contact sports should obviously be avoided while using a CGM.
What are the costs involved?

There will be costs upfront and then ongoing costs associated with having a CGM system. The costs upfront will be for the 3 components of the system and their accessories: the sensors, the transmitter, the receiver, the sensor auto-applicator and the other supplies. The ongoing costs will be for your supplies: your sensors and dressings to cover the sensors.

In the end, the cost will depend on the system that you choose and the insurance plan you have.

What are the costs involved?

No, it does not. Handheld glucose meters with test strips are needed to calibrate CGM systems.

New systems like the Dexcom G6® CGM are FDA-permitted to make diabetes treatment decisions without confirmatory test strips or calibration. However, if your glucose alerts and readings from the CGM system do not match symptoms or expectations, a handheld blood glucose meter is needed to make diabetes treatment decisions.

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  1. Touch Endocrinology. 2018.Selecting the Appropriate Continuous Glucose Monitoring System. [Accessed 5 September 2018].
  2. The Diabetes Council. 2018.Continuous Glucose Monitoring: Everything You Need to Know. [Accessed 5 September 2018].
Author Picture

Jason Collier

I am a current masters student at the University of Cape Town in South Africa. I recently completed my Bachelor of Engineering in Mechatronics, but decided to follow my passion for Healthcare Technology and further my studies with a Master of Science in Biomedical Engineering. I started HealthTechHub.net to use as a platform to discuss the latest developments in the Health Tech & Digital Health fields!