FreeStyle Libre 3

The Libre 3 sensor and app system is indicated for measuring glucose levels in the interstitial fluid (ISF) in people ≥4 years of age with type 1 or type 2 diabetes, including during pregnancy. For children (4–12 years of age), caregivers (≥18 years of age) are responsible for managing the app and sensor and interpreting the glucose readings (2). The system is intended to essentially replace fingerstick blood glucose monitoring with a glucose meter to inform daily diabetes self-management, track patterns of hypoglycemia and hyperglycemia, and assist with therapy adjustments for acute and long-term care (3). That being said, fingerstick methods should be used if Libre 3 readings do not match symptoms or expectations.

The Libre 3 system’s subcutaneous electrochemical sensor measures glucose levels in the ISF using the enzyme glucose oxidase. Glucose is oxidized by the enzyme in the ISF and transfers electrons to the sensor’s electrode, which produces a current. The system then converts the strength of the current signal to a blood glucose value for users to view in the app (4). The sensor measures glucose levels every minute and wirelessly streams the data to the Bluetooth-enabled app. In the app, a digital logbook displays the most recent 14 days of glucose readings, in contrast to the most recent 8 hours of glucose readings that are available with the Libre 2 system (3). The system is factory calibrated, so users do not need to perform fingerstick glucose checks to calibrate it at the start of or at any time during its use.

The Libre 3 system offers several advantages that may be appealing to people with diabetes and their health care providers. Applying the sensor causes little or no pain, and, as previously mentioned, no fingerstick blood glucose checks are needed to calibrate or use the system.

The Libre 3 sends valuable data automatically to the system’s smartphone app so patients will not miss readings if they neglect to scan the sensor, as they might when using the Libre 2 system. The Libre 3 offers alarms for current or impending hyperglycemia and hypoglycemia to assist patients in managing their insulin dosing and preventing serious complications from high or low blood glucose levels. This new system will also allow providers to obtain more robust glucose readings when patients are exercising or during meals over the course of 14 days (2).

To date, the Libre 3 system features the smallest dermal glucose sensor of any CGM system on the market, measuring approximately the size of a penny. The small sensor is more discreet than larger CGM sensors and enhances patient comfort when wearing a sensor continuously for 2 weeks.

All of these advantages will likely increase patient adherence to CGM therapy, which in turn will supply dynamic, accurate information that will better inform providers’ recommendations for therapeutic changes and patients’ daily treatment and lifestyle decisions.

There are not a lot of disadvantages with the Libre 3 system except for its warm-up time and the minimal age limitation for its use. The warm-up time is 1 hour compared with traditional blood glucose meters, some of which are ready to measure glucose concentrations in 5 seconds (2,5). This delay could be a disadvantage when patients urgently need a glucose reading around the time of sensor insertion. The FDA has approved the Libre 3 system for use in people ≥4 years of age, in contrast to the Dexcom G6 and Medtronic Guardian 3 CGM systems, which are indicated for patients ≥2 years of age. Because the Libre 3 system will cost less than these other CGM systems, extending its approved use to a younger patient population would be beneficial.

According to the manufacturer, the Libre 3 system should be available in retail pharmacies by the end of 2022 and will cost the same as the Libre 2 system (1). The cost of the Libre 2 is $135 for 28 days (two 14-day sensors). Most commercial insurance plans and Medicare cover the FreeStyle Libre system for patients with type 1 or type 2 diabetes with insulin use and in some cases may cover the system for patients who are not managed with insulin. Most plans do not require prior authorization to obtain the FreeStyle Libre 2, but they do require prior authorization for other CGM system that cost more. Presumably the Libre 3 will be similarly covered; however, this may vary from plan to plan.

The results of a clinical trial evaluating the accuracy of the Libre 3 system were recently published in abstract form (6). The purpose of the study was to evaluate the accuracy of the system in people ≥4 years of age with type 1 or type 2 diabetes requiring insulin therapy (6,7). This nonrandomized, multicenter, single-arm study involved 100 patients, of whom 95 were ≥6 years of age. Each patient wore up to two Libre 3 sensors and also underwent venous blood glucose testing using the Yellow Springs Instrument Life Sciences 2300 Stat Plus (YSI2300) system (2). The results showed that 93% of the CGM values were within ±20 mg/dL of the laboratory values, yielding an overall mean absolute relative difference (MARD) of 7.9%. The lower a MARD percentage is, the more accurate the system’s measurements are. This 7.9% MARD is the lowest MARD among available CGM systems to date (6).

The FreeStyle Libre 3 CGM system allows users to obtain a constant flow of accurate glucose readings in real time with data and convenient reports viewable on their smartphone. This system will allow patients, family members, caregivers, and health care providers to access the app to better assist in glycemic management. This can all be accomplished without the need for users to scan the sensor with their smartphone or a reader device, as was required with the Libre 2 system. Thus, the Libre 3 will offer more convenience and greater user-friendliness coupled with a reasonable cost to patients and third-party payers.