Four main companies in the U.S. currently manufacture CGM systems: the Abbott FreeStyle Libre 2 and 3 systems, the Dexcom G6 and recently introduced G7 systems, the Senseonics Eversense CGM, and the Medtronic Guardian Connect CGM system. Each CGM system is FDA-approved and available by prescription only. Each has its respective pros and cons.
- In general, the FDA-cleared systems are intended for use by individuals with type 1 diabetes and type 2 diabetes who are on insulin therapy and require several daily monitoring of glucose levels for frequent adjustments of the insulin treatment based on glucose levels.
Recently, the Dexcom Stelo Glucose Biosensor System was approved by the FDA as the first over-the-counter (OTC) CGM and cleared for use in adults 18 years or older with or without diabetes who do not use insulin. This system is not intended to be used if an individual who uses insulin is under 18 years old or might have hypoglycemia, nor is it designed to alert individuals with hypoglycemia. The system could be helpful for individuals who have difficulty obtaining a prescription for a CGM or whose insurance plan may not cover a CGM.
The accuracy of CGMs may vary under some conditions and for unclear reasons.
- All commercial CGMs are extensively tested for accuracy before being commercially available. In the U.S., all FDA-approved CGMs and BGMs must be within 15% of the actual laboratory blood glucose value at least 95% of the time. Accuracy studies for most CGMs typically have shown that glucose readings are within about 10% of the actual blood glucose value.
- Fingerstick testing using a BGM or glucometer is considered more accurate for blood glucose levels than CGMS. For this reason, CGMs are typically calibrated, and results are verified using fingerstick readings.
- Several factors and conditions can affect the accuracy of CGMs. They may include differences between interstitial fluid and capillary blood results, interfering substances, low compression, and other factors such as extreme temperatures and sweating.
Based on clinical studies, CGMs used to monitor glucose levels can provide the following benefits:
- CGMs can help manage an individual’s diabetes by predicting low and/or high glucose levels and tracking glucose trends over time.
- Type 1 and 2 diabetics can use CGMs to help lower Hgb A1c levels.
- CGMs can assist in lowering the chance of acute diabetes complications such as ketoacidosis (DKA) and severe hypoglycemia.
- CGMs can help make better medication, food, and exercise decisions.
- CGMs can decrease or eliminate the need for daily or frequent fingersticks for assessing blood glucose levels.
The American Diabetes Association (ADA) currently has several recommendations on using CGMs.
- In general, the ADA recommends that continuous glucose monitoring should be offered for diabetes management in adults with diabetes (and in youth with type 1 or type 2 diabetes) on multiple daily insulin injections or insulin infusion.
CGMs can be affordable with insurance coverage. Most health insurers will cover some or all of the cost if a patient meets specific criteria, such as being a type 1 or type 2 diabetic, having insulin usage requiring frequent daily adjustments based on CGM values, and checking glucose levels at least four times a day. Typically, insurers will not cover costs for CGMs if the patient does not have diabetes, prediabetes, or gestational diabetes.
