A Continuous Glucose Monitor (CGM) is a medical device that fundamentally changes how individuals track their blood sugar levels, moving beyond the traditional finger-prick method. This technology uses a small, disposable sensor inserted just under the skin, typically on the arm or abdomen, to measure glucose in the interstitial fluid. The primary purpose of a CGM is to provide a comprehensive, real-time picture of glucose trends throughout the day and night, revealing patterns that a single finger-prick test cannot capture. By continuously monitoring these levels, a CGM helps users and healthcare providers make more informed decisions about diet, exercise, and medication adjustments.
The Current Landscape of Continuous Glucose Monitors
The CGM market features several established systems, each offering a distinct approach to glucose monitoring. The Dexcom G7 is a prominent system that combines the sensor and transmitter into a single, disposable unit, known for its small size and all-in-one design. The FreeStyle Libre 3 system is another major contender, distinguished by having the world’s smallest and thinnest sensor, which automatically sends real-time readings to a compatible smartphone. Medtronic offers the Guardian 4 system, which is designed for integration, often pairing with the company’s MiniMed insulin pumps. For users seeking a longer-term solution, the Eversense E3 is the only system with an implantable sensor that can be worn for up to six months.
Comparing Sensor Technology and Functionality
The technical specifications of available CGM systems reveal significant differences in user experience and performance. A key metric for differentiating devices is sensor wear time, which dictates how frequently the user must apply a new sensor. The Dexcom G7 offers a 10-day wear time, while the FreeStyle Libre 3 provides 14 days, and the Eversense E3 extends this to 180 days with a single insertion. Measurement accuracy is quantified by the Mean Absolute Relative Difference (MARD).
The majority of modern systems, including the Dexcom G7 and FreeStyle Libre 3, are factory-calibrated, meaning they do not require routine finger-prick blood samples to maintain accuracy. The Medtronic Guardian 4 and Eversense E3 systems, however, may still require occasional calibration checks with a blood glucose meter, particularly during the initial warm-up period. Physical attributes also vary, as the FreeStyle Libre 3 is noted for its discreet size, while the Eversense E3 is unique for its under-the-skin surgical insertion, which is performed by a healthcare professional.
Interpreting CGM Data and Alerts
The way a CGM system transmits and presents glucose data directly influences the user’s ability to act on the information. Systems like the Dexcom G7 and FreeStyle Libre 3 provide real-time data, automatically sending a new glucose value every one to five minutes to a smartphone or dedicated receiver without the need for scanning. Other systems, like the FreeStyle Libre 2, operate as a flash glucose monitor, requiring the user to physically scan the sensor with a reader or phone to retrieve the current glucose value and trend data.
A significant feature across all systems is the use of predictive alerts, which notify the user not just when glucose is high or low, but when it is trending rapidly toward a dangerous level. Many systems also incorporate robust data-sharing capabilities, allowing a user to transmit their glucose numbers to designated followers for remote monitoring. Furthermore, a growing number of CGMs, including the Dexcom G7 and Medtronic Guardian systems, are designed to integrate seamlessly with external devices, such as automated insulin delivery pumps and smartwatches.
Obtaining and Affording a CGM System
Acquiring a CGM system begins with obtaining a prescription, as these devices are classified as medical devices and must be prescribed by a healthcare provider. The prescription is necessary whether the device is being used for intensive diabetes management or for general wellness tracking. The cost and method of acquisition are heavily influenced by insurance coverage, which typically falls into one of two categories.
Some systems are covered under the pharmacy benefit, similar to how prescription medications are filled, allowing for quick access at a retail pharmacy. Conversely, other systems may be classified as Durable Medical Equipment (DME), which often requires the prescription to be filled through a specialized medical supplier and can involve different co-payments or deductibles. General factors influencing out-of-pocket costs include the patient’s insurance plan, whether they have Medicare or Medicaid, and the specific coverage criteria.