CGM: Continuous Glucose Monitor


Today’s CGMs — continuous glucose monitors — put diabetes management into the 21st century. This small wearable device provides people with diabetes the blood sugar information we need to make daily management decisions.

Improving both our short and long-term health and safety, CGMs should be considered the standard of care for anyone of any age with any type of diabetes.

What is a CGM?

A CGM is a small wearable device that tracks your blood sugar levels in real-time throughout the day and night. At any moment, without pricking your finger, you can see not only what your blood sugar level is but also what direction it’s headed in.

With personalized settings, CGMs can alert you to high or low levels while also charting your blood sugar about every 5 minutes on a graph on your Smartphone or separate receiver device.

Compared to checking your blood sugar with a drop of blood on a test-strip, the information a CGM can provide both you and your healthcare team can help you adjust your diabetes management regimen and improve your overall safety around highs and lows.

*Watch this video to learn more about the differences between readings from your glucose monitor vs. a CGM sensor.

How a CGM Works

While each brand of CGM technology works slightly different, they have many similarities. (*Most of the details described below do not apply to Senseonics’ implantable Eversense CGM technology.)

  • Most CGM sensors consist of three parts: sensor (which sits in the skin), the transmitter (sits above the skin), the receiver (either your Smartphone or a handheld device that receives blood sugar data).
  • Most CGM sensors (a very thin wire-like piece) sit in subcutaneous tissue (body fat). The sensor is usually inserted with an easy at-home application device that inserts the sensor with a fine needle. The needle instantly retracts, leaving the sensor in place.
  • The visible portion of a CGM is the transmitter, which is sits on top of the skin with an adhesive that holds the entire device in place.
  • CGM sensors can be placed in several areas of your body, depending on what is most comfortable for the user: back of the arm, side/front torso, lower back, buttocks area, outer thigh, etc. 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 sensor is easy and virtually painless.
  • Varying based on brand and model, most CGM sensors need to be replaced every 2 weeks.

The Benefits of a CGM

A few of the benefits of using a CGM include:

  • Seeing your blood sugar level at any moment without pricking your finger
  • Seeing the direction of your blood sugar: rising/falling, gradually/quickly
  • Learning how/when your body responds to food, activity, hormones, stress, etc.
  • Customizable settings to alert you when your blood sugar falls below a certain level
  • Customizable settings to alert you when your blood sugar rises above a certain level
  • Catch and treat high blood sugars sooner
  • Catch and treat low blood sugars sooner
  • Help you reach your overall A1c and blood sugar goals
  • Learn what percentage of the day you are in/above/below your goal blood sugar ranges (also known as “time in range” or TIR)
  • Can integrate with your insulin pump (with additional features for closed-loop systems)
  • Share your CGM data with your healthcare team
  • Share your real-time CGM data with family or friends to see at any time on their Smartphone
  • Review your blood sugar levels at any time with helpful graphs and analytics

How do I get a CGM?

Getting a CGM starts with asking your doctor to write the prescription. Talk to your doctor about your device options and decide together which might be best for you.

Check what brands are covered under your insurance plan (including patients on Medicaid and Medicare). For example, Dexcom’s CGMs are covered by Medicare. Abbott’s FreesStyle Libre is also covered by Medicare for those who qualify.

To receive a CGM under Medicare or Medicaid, please contact your local state health exchange to check your eligibility.

Some brands also offer complimentary trial periods for new users, like Hello, Dexcom or MyFreeStyle Program. The MyFreeStyle Program allows eligible people to try either the FreeStyle Libre 14 Day System or the FreeStyle Libre 2 system. After your eligibility is determined, you’d request a prescription from your healthcare provider and get guided support from 14 days of emails tailored to your personal journey.

CGMs Available Today

Here are today’s available CGM brands and models. This technology has evolved rapidly over the last decade, improving in ease-of-use, accuracy, and connectivity with other technology.

Dexcom: G5 & G6

Dexcom’s current models include the G5 and G6. A leader in CGM technology, Dexcom has gradually reduced the overall size of the transmitter while increasing the accuracy and ease-of-use since the earlier models.


  • Measures your blood sugar every 5 minutes
  • Does not require finger-stick calibration with a glucose monitor
  • Communicates directly with your Smartphone or receiver
  • Integrates with Tandem T:slim and Omnipod insulin pumps
  • Can be used without an insulin pump
  • 2-hour warm-up period after inserting new sensor before usable
  • Sensor lasts 7 days


  • Has all the features of the G5
  • No calibration required
  • Easier sensor applicator than G5
  • Can predict oncoming lows
  • Sensors lasts 10 days
  • Integrates with the Tide Pool closed-loop system

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Medtronic: Guardian Connect

Medtronic’s Guardian Connect has evolved over the years, improving in accuracy and ease-of-use. It is the only CGM option for those using Medtronic insulin pumps who want an integrated system.

  • Measures your blood sugar every 5 minutes
  • Requires finger-stick calibration twice per day
  • Communicates directly with your Smartphone or receiver
  • Integrates with 670, 770, (780G soon) Medtronic insulin pumps
  • Can be used without an insulin pump
  • 2-hour warm-up period after inserting new sensor before usable
  • Sensor requires charging
  • Sensors lasts 7 days
  • Integrates with the Tide Pool closed-loop system

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Abbot: Freestyle Libre 2 & Libre 14-Day

The Freestyle Libre technology is the only CGM available at your local pharmacy versus shipments directly from the manufacturer. It’s also the most affordable, making it more accessible to those without insurance coverage.

Libre 14-day

  • Actually a “flash” glucose monitor, it communicates readings when you swipe sensor with your Smartphone
  • No calibration required
  • Warm-up period of 1 hour
  • Easy sensor application process
  • Sensor lasts 14 days

Libre 2

  • Measures your blood sugar every minute
  • No calibration required
  • Greater accuracy than 10-day system
  • Warm-up period of 1 hour
  • Features 8-hour historical trend
  • Sensor lasts 14 days

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Senseonics: Eversense

The newest of CGM technology, the Eversense CGM system is implanted beneath the skin. Unlike other CGM technology, the sensor is entirely beneath the skin, without any visual puncture site, while the transmitter is simply placed above the sensor area with an adhesive.

  • Inserted by a doctor every 90 days (365-day sensor available in Europe)
  • Sensor implanted beneath the skin
  • Can remove the external transmitter without removing sensor
  • Transmitter provides on-body vibration alarms even if phone is out-of-range
  • Studies show it may be more accurate than any other existing CGM technology
  • Requires additional costs associated with doctor appointments and procedures
  • May be difficult to get because doctors must be trained by Senseonics for implantation procedure

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