6 Best Continuous Glucose Monitors for 2024

Editor’s Note: T1DStrong constantly updates articles to reflect new developments and resources for T1D individuals. See below the new advancement—Asensia's Eversense® 365. It’s the only CGM with a removable transmitter and requires a single warmup period every year.

If you’re newly diagnosed with type 1 diabetes (T1D), chances are that you’ve learned a great deal of diabetes-related tech terminology in a short window. Not only is the disease itself overwhelming, but now you must decide which blood glucose meter (BGM), insulin pen, insulin pump, or continuous glucose monitoring system to use.

Hopefully, you have an excellent physician and healthcare team to weigh all the options with you.

If you have the luxury of choosing a continuous glucose monitoring system, it provides a safety net against extremely low and high blood glucose levels. This added comfort helps T1Ds better manage blood sugar levels and removes the annoyance of painful finger pricks from a BGM.

Also, continuous glucose monitoring can benefit all types of insulin delivery therapy (daily multiple injections (DMI), insulin pumps or pens).

What is a Continuous Glucose Monitor (CGM)?

CGMs are wearable diabetes tech used to help manage blood glucose levels. The small device has a sensor worn under the skin that sends a signal to a transmitter/smartphone that shows the results.

Individuals can attach the sensor to their arms or stomach, where it automatically estimates their blood sugar level. The tiny needle stays under the skin, and the lengths vary according to your monitor type.

This real-time facet of CGMs is impressive, with calculations improving since its inception. Most health insurance plans cover CGMs, but you need a prescription. The exception to this is Dexcom's new Stelo CGM, which can be purchased over-the-counter (OCT).

Interesting Fact: The Centers for Medicaid and Medicare Services recently expanded coverage of CGMs to include all insulin-dependent people.

Should I Get a CGM?

The recommendations for acquiring a continuous glucose monitor are increasingly favorable. The American Diabetes Association (ADA), Breakthrough T1D (formerly JDRF), the National Institutes of Health, and the Endocrine Society all say CGMs help individuals with type 1 and type 2 achieve their glycemic targets.

Doctors especially advocate CGMs for people with problematic hypoglycemia and hypoglycemic unawareness, which occurs when an individual doesn't feel a low blood glucose episode. Hypoglycemic unawareness affects about 40% of people with type 1 diabetes.

CGMs are considered a closed-loop system or artificial pancreas connecting to an insulin pump acting as the body's pancreas.

When choosing a CGM, you must consider many factors besides its unique bells and whistles: price, ease of use, connectivity, accuracy, and data management.

6 Best CGM Devices

T1D Strong has broken down the six best monitors to review, all of which have been approved by the FDA.

Dexcom G6

Pros for the Dexcom G6 are that it is simple to insert with the push of a button, and the sensors are preloaded into the insertion device. After the two-hour warm-up, the Dexcom CGM shows glucose readings stored via the receiver or an app installed on your smartphone. The waterproof sensor can last up to 10 days, and the transmitter lasts three months, after which it must be replaced. (The major con with the G6 compared to the G7 is the warm up time. G6's warm up time takes up to two hours, and the G7 is only 30 minutes.)

The Dexcom G6 is the best for pairing with an Apple Watch or iPhone. Also compatible with Android phones and other glucose-monitoring apps, it provides high and low glucose alerts with arrows trending in either direction, informing you where your glucose levels are headed. The G6 has a high level of accuracy. The FDA approved the G6 to alter the insulin level administered by a wirelessly connected insulin pump.

Interesting Fact: People without diabetes with a history of hypoglycemia or individuals who simply want to control their diets are wearing CGMs.

Dexcom G7

The Dexcom G7, released in early 2023, has many updated features from the G6. Most notable is the size; the G7 is 60% smaller than the G6, with a more circular shape, similar to the Freestyle Libre. Being smaller, it’s more comfortable and less intrusive.

Another benefit on the G7, in addition to the shorter warm up time of 30 minutes is the G7 has a one-step application process, and the G6 has a two-step. he G7 provides increased accuracy, a 12-hour grace period to change the sensor when it expires after 10 days of usage.

Stelo by Dexcom

Dexcom's new Stelo, is the first FDA approved glucose biosensor designed for people living with type 2 diabetes (T2D), and the first OTC CGM available without prescription. Stelo is built on the same Dexcom G7 platform, but it's intended for a T2D audience and manufactured with different software and user experience. Stelo users are typically individuals who aren't insulin dependent. The G7 has alerts for low blood glucose levels for insulin users, while the Stelo sends phone alerts for glucose spikes.

The Stelo app focuses on real-time insights and glucose trends and the G7 is laser focused on low blood sugar alerts. Stelo's sensor lifespan is a bit longer, lasting 15 days to the G7's 10 days. The sensor warm-up/calibration period is about the same as the G7, a 30-minute warm up time.

Abbott Freestyle Libre 2 & 3 CGMs

The Freestyle Libre system (Abbott Freestyle Libre 2 and Abbott Freestyle Libre 3) is one of the easiest CGMs to use, but it’s a Flash CGM, meaning you have to flash your phone over the CGM to receive a reading. The device is small in size, comparable to the Dexcom G7. The Freestyle lasts up to 14 days – being the longest CGM available (with at-home application) and reasonably priced when matched to its competitors. It’s touted as being the least expensive without insurance. The device usage is only approved for the back of the arm, not the stomach. The Freestyle Libre is compatible with both iOS and Android Phones, and the application is easy for both, followed by the scanning process, which can be done through clothing.

Freestyle Libre 2 & Freestyle Libre 3

Both the Libre 2 and Libre 3 versions have a 14-day sensor length and are sold for the same price. One difference between the two is that the Freestyle Libre 3 is smaller (the size of a penny in diameter), while the Libre 2 is the size of a quarter. The other variance is accuracy. The Freestyle Libre 3 has a MARD score below 8%, making it the most accurate on the market. The Libre 2’s MARD score is 9.2%

Another perk with the Freestyle Libre 3 is that it doesn’t provide a reader and doesn’t require phone scanning, as it updates the data every minute.

Pro Tip: MARD (Mean absolute relative difference) is the standard way to measure CGM accuracy. For example, the Dexcom G7 claims an 8.2% for adults (with stomach insertion), and the G6 has a MARD of 9% for adults inserted into the stomach. The smaller the MARD score, the closer the CGM readings are to the real glucose value, while a larger MARD score suggests more discrepancies. Most systems have an average MARD of 9-14%.

Medtronic Guardian™ 3 Connect System

The Medtronic Guardian is small, like the Libre and Dexcom G7 and can be inserted into the stomach or back of the upper arm. The insertion process is a little more complicated and time-consuming as users must apply tape to the device. Also, the sensors must be replaced weekly, unlike the other systems that last two weeks or longer. This CGM tracks blood glucose trends and collects data. The longer you use the app, the more data gathered and the more accurate its reports will be. The Guardian is known for the best spike warnings. After insertion, the transmitter provides direct readings every five minutes.

The Medtronic Guardian 3 can connect to its Medtronic insulin pump. While it is compatible with iOS and Androids using the Guardian Connect app, it does not work with other glucose monitoring apps.

Pro Tip: Most CGMs provide apps to allow friends, family, and caregivers to help monitor glucose levels.

Eversense® 365

Ascensia Diabetes Care recently launched Eversense 365, a one-year implantable CGM for adults with diabetes. As the only CGM with a removable transmitter which can be easily taken on and off without wasting a CGM or adding a warmup period, Eversense® 365 requires a single warmup period every year. 

Following the recent FDA approval, this new development is transforming diabetes management, as Eversense is now the World’s First One-Year CGM. One implanted sensor provides long-term, year-round usage versus 10-14 days of short-term CGM service. Eversense 365 reduces the burden of data interruption and sensor failures. Other benefits include more freedom, comfort, improved discretion, and on-body vibration alerts that notify patients even when their mobile phone is out of sight. Eversense 365 will be available in the U.S. in the fourth quarter of 2024 for those with commercial insurance.

Similar to the Eversense 365, the Eversense® E3 tracks glucose levels up to 180 days and has a notable MARD score of 8.5%. The only caveat is that these CGMs are subcutaneous devices implanted underneath the skin and needs the assistance of a medical professional. The procedure is not painful but does require additional medical costs for clinical visits.

Consequently, it is only approved for use by adults 18 years of age and older, while most other devices can be used with children as young as two. Another drawback is the 24-hour warm-up time compared to other CGMs. So, naturally, Eversense ranks high with ease of use and low maintenance. It is also compatible with Android and iOS phones and has its mobile app, the Eversense. However, it is not compatible with other glucose monitoring apps.

Other Monitoring Devices

Flash Glucose Monitoring

The term flash glucose monitor (FGM) is a sensor that measures glucose readings and displays the information on your mobile phone. The device is typically worn on your upper arm, and like the CGM system, it measures the interstitial fluid under your skin.

The difference between a flash glucose monitor and a CGM is that the blood glucose reading shows up on your device or mobile app automatically via Bluetooth, whereas with flash glucose monitoring, you must wave or scan your device over your sensor to see the glucose level.

The Abbott Freestyle Libre 2 is a type of flash glucose meter that is also a continuous glucose monitoring device. Your health care provider should be able to assist you in deciding which personal CGM device is best for you.

Bottom Line: CGMs are a Life-Saving Technology

If you are fortunate enough to try a CGM system, these AI-tracking devices are the future of diabetes care. Glucose meters and syringes may one day be a thing of the past. Just as smartphone apps and smart devices are a part of everyday life, diabetes technology is growing exponentially to the point where commercial insurance companies will be forced to cover most individuals.

The CGM sensors keep getting smaller, they provide excellent target range, and the devices make it easier for patients to participate in clinical trials. CGM systems allow T1D individuals increased wearability and reliability by adding the freedom to pursue intense physical activity and lengthy outdoor adventures.

CGMs allow T1Ds control over their condition with continuous feedback. If you want to participate in your diabetes care proactively and can afford one, CGMs stand out. They help you make informative decisions based on actual statistics and can be a game changer for improving your hemoglobin A1c level and overall health.