CGM technology is utilized by patients with type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM) who require insulin injections or pumps. CGM devices constantly sense and relay glucose concentration data from the interstitial fluid to a mobile phone, smart watch, or receiver. Depending on the device, glucose concentrations are measured every 5 to 15 minutes. CGM provides a comprehensive picture of glucose fluctuations across time, and fluctuations scan be linked to life events such as meals, exercise, sleep, or medication administration.

Studies have shown that the use of these devices, compared with self-monitoring blood glucose meters, improved patient glycemic control. In addition, research has shown that with improved glycemic control and subsequent decreases in hypoglycemic events, patients have improved clinical outcomes and overall health-related quality of life.

The integration of CGM technology into clinical practice has expanded rapidly and is associated with numerous clinical benefits, including accuracy, affordability, and accessibility. Blood glucose meters require frequent and often painful finger sticks throughout the day to obtain a single reading at a moment in time. In contrast, CGMs provide continuous real-time glucose readings 24/7 to a compatible smart device or receiver and have proven accuracy without the need for frequent, painful, and inconvenient finger sticks.

The American Diabetes Association (ADA) notes that CGM devices are particularly valuable for alerting patients to previously unrecognized hypoglycemic episodes. The glucose management indicator (GMI) and data on time in range (TIR), hypoglycemia, and hyperglycemia are available to providers and patients via the Ambulatory Glucose Profile (AGP) report, which offers visual cues and recommendations to assist in data interpretation and treatment decision-making.

There are two basic types of CGM devices: those that are owned by the user, unblinded, and intended for frequent/continuous use, including real-time CGM (rtCGM) and intermittently scanned CGM (isCGM), and professional CGM devices that are owned and applied in the clinic and provide data that are blinded or unblinded for a discrete period of time. The selection of device should be made based on the individual’s circumstances, preferences, and needs.

The 2023 ADA guidelines recommendations for CGM devices include:

• Real-time CGM or intermittently scanned CGM should be offered for diabetes management in adults with diabetes on multiple daily injections or continuous subcutaneous insulin infusion who are capable of using the devices safely (either by themselves or with a caregiver).
• Real-time CGM or intermittently scanned CGM should be offered for diabetes management in adults with diabetes on basal insulin who are capable of using the devices safely (either by themselves or with a caregiver).
• Real-time CGM or intermittently scanned CGM should be offered for diabetes management in youth with T1DM on multiple daily injections or continuous subcutaneous insulin infusion who are capable of using the devices safely (either by themselves or with a caregiver).
• Real-time CGM or intermittently scanned CGM should be offered for diabetes management in youth with T2DM on multiple daily injections or continuous subcutaneous insulin infusion who are capable of using the devices safely (either by themselves or with a caregiver).
• In patients with diabetes on multiple daily injections or continuous subcutaneous insulin infusion, real-time CGM devices should be used as close to daily as possible for maximal benefit. Intermittently scanned CGM devices should be scanned frequently, at a minimum once every 8 h. Patients with diabetes should have uninterrupted access to their supplies to minimize gaps in CGM.
• When used as an adjunct to pre- and postprandial blood glucose monitoring, CGM can help to achieve A1C targets in diabetes and pregnancy.
• Periodic use of real-time or intermittently scanned CGM or use of professional CGM can be helpful for diabetes management in circumstances where continuous use of CGM is not appropriate, desired, or available.
• Skin reactions, either due to irritation or allergy, should be evaluated and addressed to aid in effective use of devices.
• CGM device users should be educated on potential interfering substances and other factors that may affect accuracy.

Currently, there are multiple FDA-approved CGM devices approved for use in patients with diabetes: Dexcom G6 and Dexcom G7 (Dexcom), Medtronic Guardian Connect, FreeStyle Libre 2 and FreeStyle Libre 3 (Abbott), and the implantable Eversense (Ascensia Diabetes Care/Senseonics).

Dexcom was one of the first developers of CGM technology, introducing the first-ever real-time CGM, and its first product, Dexcom G6, uses a sensor that lasts for 10 days, requires no calibration, and is approved for patients aged as young as 2 years. In December 2022, the FDA approved next-generation Dexcom G7 CGM for use in patients aged 2 years and older with all types of diabetes. The manufacturer decreased the size of the wearable device by 60% compared with its previous generation, Dexcom G6. With fewer components, Dexcom G7 offers a 30-minute sensor warmup time along with a 12-hour grace period for replacing finished sensors, which provides smoother transitions between sessions. It features a redesigned and simplified mobile app, which includes integration with Dexcom Clarity, as well as improved alert settings for enhanced discretion.

Medtronic Guardian Connect is approved for those aged 14 to 75 years with T1DM and T2DM and includes a sensor that needs to be changed every 7 days.
Freestyle Libre is available as Freestyle Libre 2 and Free style Libre 3. In October 2023, the manufacturer released an updated ap with a silent mode that delivers signal loss and glucose alarms without sound or vibration for up to 6 hours in 5-minute increments. While in silent mode, visual notifications still appear on the smartphone’s lock screen, so users can view them at their convenience. In May 2022, the FDA approved the Freestyle Libre 3, which includes a 14-day sensor and no finger-stick calibrations. In August 2023, the manufacturer announced that FreeStyle Libre 3 reader was made available in the U.S., enabling patients on Medicare to access the system.

Eversense E3 is the only implantable sensor device for long-term wear and requires a visit to the primary healthcare provider every 6 months to change the sensor. It also provides silicone-based, fresh-daily adhesive for comfort. Eversense requires twice-daily finger-stick calibration and is the only CGM that has a distinct on-body vibe alert when a patient is hypoglycemic or hyperglycemic.

The content contained in this article is for informational purposes only. The content is not intended to be a substitute for professional advice. Reliance on any information provided in this article is solely at your own risk.