CGMs, or continuous glucose monitors, puts diabetes management into the 21st century. This small wearable device could be considered the next step in blood glucose testing, and your next step to better diabetes management.

What is a CGM?

A CGM is a small wearable device that tracks your glucose throughout the day and night, notifying you of highs and lows to give you a clear picture of your blood sugar levels.

The continuous glucose monitor automatically checks your blood sugar every 5 minutes and displays your “numbers” on a screen. It also features a convenient application that is accessible to iPhone and Android users.

Dexcom’s G4, G5, G6Abbott’s Freestyle Libre and FreeStyle Libre 14-Day System, Medtronic’s Guardian Connect, and Eversense from Senseonics all offer the option to allow glucose readings to go on a smartphone, or even a smart watch. The application on your smartphone also features a Share component, in which you can share your blood glucose readings to another person’s smartphone. Both the user and the Share recipient will receive notifications of highs and lows, and is a fantastic way to keep an eye out for a friend.

Additional resources

The CGM consists of three basic parts:

  • wireless display device (or receiver) –  has a screen where you can check your current glucose level, look at past data over a span of 24 hours, and get trends about whether glucose is likely to go up or down, and how fast.
  • transmitter –  is the small piece that fits onto the sensor and sends glucose information data wirelessly to your display device.
  • sensor – is inserted just underneath the skin, is thinner than a needle and roughly half an inch long. The sensor remains in the skin for several days, detecting glucose information.

How a CGM Works

The CGM can be placed in several areas of your body, depending on what is most comfortable for the user. The most popular places for a CGM tend to be around the stomach, back of the arms and legs. Avoid spots where your body naturally bends a great deal, where clothing might cause irritation or be a burden.

The process of inserting the CGM is easy and virtually painless. For anywhere from 1 week to 3 months, you can have direct access to your blood sugars throughout the day and night.

The Benefits of a CGM

Finger pricking in the morning, two hours before and after meals, before and after physical activity, at bed, and whenever you feel symptomatic is unrealistic, even to the most tightly controlled diabetics. Cue the beauty of a CGM.

The CGM is a way for you to quickly glance at your device and determine where you are standing as far as your levels go. You will get a notification if your level dips below 80, and you will get a notification if your level spikes above 200. You have the ability to change these notifications based on your diabetic control.

The CGM is able to withstand the active lifestyle of a person with Type 1. The qualities of this device, the easy insertion and the amazing capabilities of this device make them a must-have for someone with diabetes.

CGM Device Comparison
     Device  Release   Life           Description
Dexcom’s G4 2012 7 days
  • Tracks glucose levels at 5 minute intervals
  • High and low alarms
  • High level of accuracy – MARD value 13% in adults
  • Alerts rate of glucose levels rising/falling
  • Integrated with Animas Vibe insulin pump
  • Calibration with blood glucose recommended at least twice daily
  • Requires a CGM receiver
Dexcom’s G5 2017 7 days
  • Has all the same features as G4, plus …
  • Doesn’t require a CGM receiver – you can use your smartphone to receive data
  • Larger trend graph display than G4
  • Integrated with Tandem’s T:slim X2 insulin pump
Dexcom’s G6 2018 10 days
  • Has all the same features as G5, plus …
  • Easier set up (no fingerstick, easy sensor applicator)
  • Predicts lows


Freestyle Libre

2017 10 days
  • Actually a flash glucose monitor – doesn’t continuously communicate readings
  • No fingersticks necessary
  • Can’t be manually calibrated  
  • Warm-up period of 1 hour


Freestyle Libre 14-Day System

2018 14 days
  • Utilizes flash glucose monitoring – doesn’t continuously communicate readings
  • No fingersticks necessary
  • Greater accuracy than 10-day system
  • Warm-up period of 1 hour
  • Features 8-hour historical trend


Guardian Connect

2018 7 days
  • Sends data straight to iPhone, like the G5
  • No option of a non-iPhone receiver
  • Doesn’t need a pump to use the Guardian Connect
  • Sensor also requires charging
  • Requires a separate inserter, unlike G6



2018 90 days
  • Capable of providing 90-day continuous wear
  • Remove the transmitter without removing the sensor
  • Transmitter provides on-body vibration alarms even if your phone is out of range
  • Studies have shown Eversense to be as accurate or more accurate than currently commercially available continuous-wear sensors.
  • Requires doctors appointments and procedures every 90 days and additional associated costs

Usage Tips

CGMs are built to stay on your skin for several days. If you find the sticking part of your CGM coming off, you can use a piece of kinesiology tape, cut out a hole for your transmitter, and stick the tape on top of your CGM. You can also purchase adhesive wipes to ensure the long lasting wear of the CGM.

The benefits of a CGM makes a life with Type 1 a little easier by taking some of the questions out of your blood glucose levels. Without worry, you’ll be able to know your levels right away. Additionally, you can easily predict if you are going to be heading high or low because of the trending arrows that are shown on the display device. With this knowledge, you can actively prevent potentially dangerous situations in blood glucose management.

Implantable CGM – Eversense

Another option is the Eversense CGM System. Eversense is a management system which includes a sensor that is implanted subcutaneously — under the skin — and measures blood in interstitial fluid. This sensor communicates with a transmitter that is placed on the arm, which in turn sends the information to a smartphone. While this technology is very new and, in its current form, arguably not more user-friendly than existing technology, it’s a step away from the needles and weekly site changes that CGMs currently require.

Check out our Pumps Guide and our Blood Glucose Meter Rundown!

Read FDA Approves Dexcom G6.