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Continuous Glucose Monitors (CGM)

What do CGMs do?

Continuous glucose monitors (CGM) measure the body’s glucose levels in real-time by sensing the glucose present in tissue fluid (also called interstitial fluid). Glucose is another word for sugar. While a blood glucose meter (BGM) provides a measurement of the blood glucose level at a specific moment in time (when you prick your finger), CGMs typically provide a new glucose level every five minutes, meaning 288 times per day. A BGM is similar to a photo – providing a single blood sugar “snap shot” – while a CGM is like a video, providing a constant stream of information on glucose levels, trends, and overnight data. 

CGMs are particularly useful after meals and overnight, as they can sound an alert when glucose levels drop or rise below a preset threshold. CGMs provide a good way to monitor time spent “in range” (time spent within a normal, pre-specified blood sugar range); for more on time-in-range goals, see here and here

Some CGMs need to be calibrated with a fingerstick blood sugar reading for optimal sensor accuracy; two CGMs currently do not need fingerstick calibrations – Abbott's FreeStyle Libre (and Libre 2) and Dexcom’s G6.  

What Supplies Do I Need?

CGMs require three basic parts:

  • Sensor – monitors real-time glucose levels, usually every five minutes. The sensor is inserted under the skin by the user with a simple applicator. Sensors are normally worn for 7-14 days, depending on the system. However, the new Eversense Implantable CGM system (which includes a sensor inserted under the skin of the upper arm) can be worn for up to 90 days.

  • Transmitter – sits on top of the sensor and sends glucose information to a receiver or a smartphone app. Most systems have a transmitter that is reusable for 3-12 months. In the case of FreeStyle Libre, there is no reusable transmitter; each sensor is fully disposed after 14 days and a new one is put on.

  • Smartphone app or receiver – displays real-time glucose level, whether blood glucose is trending up or down, and glucose history. Most CGMs offer smartphone apps for viewing data. Abbott and Dexcom also offer handheld devices for people that don’t use a smartphone. Some CGM devices also send the glucose value to an insulin pump, including a growing number that can automatically deliver insulin accordingly.

What CGMs are available in the US?

Last updated: August 14, 2020

Currently, four companies have personal CGM devices on the US market: Abbott (Freestyle Libre, Libre 2, and Libre 3), Dexcom (the G4 and G5, which were discontinued in June 2020, and the G6), Medtronic (Guardian Connect and Guardian Sensor 3), and Senseonics Eversense. The table below compares some of their key features. Pricing varies with insurance coverage and can be provided by the company. For people paying out-of-pocket (with no insurance coverage), FreeStyle Libre is the least expensive CGM as of this writing.


Freestyle Libre 14-Day (US)

Freestyle Libre 2

(available in some countries in Europe, and US soon)

Dexcom G6

Medtronic Guardian Sensor 3
(used with 670G pump and Guardian Connect)

Senseonics Eversense (US)

Freestyle Libre 3

Fingerstick Calibration

0 - Factory Calibrated

0 - Factory Calibrated

0 - Factory Calibrated

2/day minimum

2/day minimum

0 - Factory Calibrated


Replaces fingersticks for treatment decisions

Replaces fingersticks for treatment decisions

Replaces fingersticks for treatment decisions

Requires fingerstick confirmation

Replaces fingersticks for treatment decisions, 

Requires 2 fingerstick calibrations per day

Replaces fingersticks for treatment decisions


18+ years

4+ years

2+ Years

7+ Years (670G)

14+ Years (Guardian Connect)

18+ Years

4+ years

Medicare coverage


Not known






1 hour

1 hour

2 Hours

2 Hours

24 hours after implantation

1 hour

Wear length

14 Days

14 Days

10 Days

7 Days

90 Days

14 Days

Alarms for Lows, Highs

None in US – must scan sensor to see glucose. 






Data display

Reader, Android and iPhone apps (FreeStyle Libre Link)

Reader (mobile app not yet available in US)

Receiver, Android and iPhone apps, smartwatches, Tandem t:slim X2 pump

630G or 670G pump, Guardian Connect Android and iPhone apps

Android and iPhone apps

Android and iPhone apps

On-body form and transmitter design 

~2 stacked quarters, one-press insertion

Fully disposable transmitter integrated with sensor patch

~2 stacked quarters, one-press insertion

Fully disposable transmitter integrated with sensor patch

Eraser-sized transmitter, one-button inserter

Three-month use transmitter separate from sensor

~2 stacked quarters (clamshell), one-button inserter

Rechargeable transmitter separate from sensor

Sensor inserted by a healthcare professional 

Rechargeable, watchface-sized transmitter separate from sensor

~2 stacked pennies, one-press insertion

Fully disposable transmitter integrated with sensor patch

Useful Links:

Abbott FreeStyle Libre

Abbott Freestyle Libre 3 Receives FDA Clearance – Overview of the features, updates, and cost of Freestyle Libre 3

FreeStyle Libre 2 Cleared by FDA as iCGM – Bluetooth connectivity allows high and low blood glucose alerts, with better accuracy and the same price as original Libre.

How to Use FreeStyle Libre Trend Arrows to Adjust Insulin Doses – Endocrine Society guidelines for insulin dose adjustments based on Libre CGM trends, suggestions for scanning time and frequency.

Abbott FreeStyle Libre 14-Day Obtains Medicare Coverage – Covered for people with type 1 or type 2 diabetes on intensive insulin therapy (multiple daily injections or insulin pump).

Abbott’s FreeStyle Libre – Transforming Glucose Monitoring Through Utter Simplicity, Fingersticks Aside! ­– Adam Brown’s test drive of the Freestyle Libre’s 14-day sensor


UnitedHealth Group Provides Dexcom G6 Through Level2 Program – Enroll in Level2 to get a CGM, a Fitbit activity tracker, and easily accessible virtual health coaching; the program is designed to help people achieve type 2 diabetes remission.

Dexcom’s Professional CGM Helps Improve Diabetes Outcomes – Want to try CGM? Professional CGM is a tool that people use for ten days with their healthcare team to better understand their blood glucose levels.

Dexcom Set to Discontinue G4 and G5 to Make Way for the G7 – In June 2020, Dexcom stopped selling G4 Platinum and G5 CGM transmitters. Starting in 2021, you will not be able to download the Dexcom Studio app.

Dexcom G6 Obtains Medicare Coverage – Covered for people with type 1 or type 2 diabetes on intensive insulin therapy (multiple daily injections or insulin pump).

Dexcom G6 CGM: No Fingersticks, One-Button Insertion, and 10-Day Wear – What’s great about the G6, what could be even better, and how the new CGM compares to the G5.


News from Medtronic: Hypoglycemia Prediction and Timing on the MiniMed 780G Closed Loop – The 780G will add automated correction boluses and Bluetooth.

What’s next for Medtronic Diabetes? A Look into CGM and Pump Pipeline – Medtronic hopes to launch at least 10 products over the next several years, including new CGM and apps, 670G pump with Bluetooth, AI, and more! Updates here.

Medtronic Announces FDA Approval of Guardian Connect Mobile CGM – Guardian Connect is Medtronic’s “standalone,” real-time, mobile CGM in the US, meaning it sends CGM information directly to a smartphone app.


Cigna Insurance to Cover Senseonics’ Eversense CGM – Cigna health insurance will now cover the 90-day implantable Eversense CGM for people with type 1 or type 2 diabetes who take insulin​, joining several other insurance companies that cover the device.

Senseonics’ Eversense Bridge Program: Cost Assistance for 90-Day Implantable CGM– Offers 90-day Eversense CGM at reduced $99 price plus the cost of sensor insertion and removal.

FDA Approves Senseonics’ Eversense 90-Day Implantable CGM, On-Body Transmitter, and Smartphone Apps – First implantable CGM available in the US. Eversense’s 90-day wear removes the need for frequent sensor insertions required by other CGMs. 

Other CGM Links 

What’s Coming and What’s Delayed in Continuous Glucose Monitoring? – Updates and delays from Abbott, Dexcom, Medtronic, and Senseonics.

Imagine 288 Fingersticks a Day: The Power of CGM – Michael Hattori shares his experience using a CGM to achieve T2D remission.

Medicaid and CGM: Who's Covered? – A guide to CGM coverage by state Medicaid programs.

Understanding Average Glucose, Standard Deviation, CV, and Blood Sugar Variability – What do these numbers mean, what’s the target, and how can they provide insight into better diabetes management? Example days included!

Time in Range: What’s an Achievable Goal with Diabetes? – Adam Brown's approach to time in range goals, five key tips to spend more time in range each day, and what’s still to come from experts.

CGM and Time-in-Range: What Do Diabetes Experts Think About Goals? – An interview with 15 experts about time-in-range goals for those wearing CGM. 

Remote Monitoring of CGM Data

Remote monitoring allows for a person’s blood glucose numbers or CGM data to be shared with others. This option is now available for many CGM devices. Learn more about uploading your data here

Remote monitoring can be used to give peace of mind to loved ones. For example, a traveling spouse can share their CGM data with family at home, or a child at a sleepover can share blood sugar levels with their parents.  People also use remote monitoring to send updates directly to their healthcare team.

How to Coach Your Care-Partner on CGM Data – Kerri Sparling gives advice for discussing data-sharing guidelines with your loved ones.

“Can I Follow Your CGM?” Having a Conversation About Sharing Your Data – Learn more about the decision to share your CGM data.

Please note, this page is not a comprehensive list of all of the available resources or products available. All links are organized chronologically within their respective sections.