Continuous glucose monitoring (CGM) emerges as a technology with the potential to provide patients, providers and health care professionals valuable information to achieve a better glycemic control while reducing the disease burden.

CGM devices measure interstitial glucose every 5 to 15 minutes, which highly correlates with blood glucose. They also provide information about trends in blood glucose levels and alert users for hypoglycemia and hyperglycemia. They consist of a glucose sensor placed under the skin, an adherent transmitter over it and a data receiver (either a portable device receiver or a smart phone or smart watch) (1, 2).

CGM provides real-time information about glucose control, allowing individuals to make timely decisions, understand glucose trends and fluctuations and adjust more precisely insulin dosing. It also helps to reduce hypoglycemia and hyperglycemia risks by providing early warnings when glucose levels are dropping or increasing. These benefits and the reduced need to frequent fingerstick tests, help to improve patients’ quality of life and reduce the burden of diabetes management.

There are three main types of CGM devices: real-time CGM, intermittently scanned CGM with and without alarms, and professional CGM (1-3).

Real-time CGM devices measure and store glucose levels continuously and without prompting. They also provide alarms to notify the user that glucose level is approaching or is in the hypoglycemic or hyperglycemic range, as well as arrows that show whether glucose is stable, increasing or decreasing quickly or very quickly.

Intermittently scanned CGM, sometimes called “flash glucose monitors”, measure glucose levels continuously but require scanning for their storage. The second generation of these devices also have alerts for hypoglycemia and hyperglycemia. Professional CGM are placed at the healthcare provider’s office and worn for a period, usually 7 to 14 days. Glucose levels may be blinded or visible for the patient. After this period, the patient returns to the health care office to download and analyze the data.

The use of these devices should always be coupled with patient’s education to adjust medication and change lifestyle behaviors.

CGM devices may be a part of the closed-loop insulin delivery systems, also referred to as the “artificial pancreas”. In these systems, insulin delivery can automatically be adjusted based on CGM data, further improving glucose control (4, 5).

CGM devices costs and concerns related to accuracy and reliability of measurements are some issues that may emerge as barriers to its use. However, CGM technology is in continuous evolution and efforts are being made by the researchers to improve sensor accuracy and to integrate the system with other diabetes management tools (1-3).

The consensus report of ADA and EASD recommended that glycemic control included, in addition with HbA1c, time in range assessment (a CGM-derived indicator) (6, 7). Noteworthy, the use of CGM in diabetic patients at high cardiovascular risk is promising and needs further evaluation according to the Delphi consensus published in Cardiovascular Diabetology (8).

Continuous glucose monitoring technology has revolutionized diabetes management by providing real-time data, glucose trends and hypoglycemia and hyperglycemia alerts, reducing the need to frequent fingerstick tests. These advantages, coupled with education and adequate follow-up, improve glycemic outcomes, reduce the disease burden and significantly improve the quality of life of people with diabetes.

References 

1. American Diabetes Association Professional Practice C. 7. Diabetes Technology: Standards of Medical Care in Diabetes-2022. Diabetes Care. 2022;45(Suppl 1):S97-S112.
2. Sacks DB, Arnold M, Bakris GL, et al. Guidelines and Recommendations for Laboratory Analysis in the Diagnosis and Management of Diabetes Mellitus. Diabetes Care. 2023;46(10):e151-e99.
3. Simonson GD, Bergenstal RM, Johnson ML, et al. Effect of Professional CGM (pCGM) on Glucose Management in Type 2 Diabetes Patients in Primary Care. J Diabetes Sci Technol. 2021;15(3):539-45.
4. Templer S. Closed-Loop Insulin Delivery Systems: Past, Present, and Future Directions. Front Endocrinol (Lausanne). 2022;13:919942.
5. Åm, M.K., Teigen, I.A., Riaz, M. et al. The artificial pancreas: two alternative approaches to achieve a fully closed-loop system with optimal glucose control. J Endocrinol Invest. 2023. https://doi.org/10.1007/s40618-023-02193-2
6. Davies MJ, Aroda VR, Collins BS, et al. Management of hyperglycaemia in type 2 diabetes, 2022. A consensus report by the American Diabetes Association (ADA) and the European Association for the Study of Diabetes (EASD). Diabetologia. 2022;65(12):1925-1966.
7. El-Sayed NA, Aleppo G, Aroda VR, et al. 6. Glycemic Targets: Standards of Care in Diabetes-2023. Diabetes Care. 2023;46(Suppl 1):S97-S110.
8. Di Mario C, Genovese S, Lanza GA, et al. Role of continuous glucose monitoring in diabetic patients at high cardiovascular risk: an expert-based multidisciplinary Delphi consensus. Cardiovasc Diabetol. 2022;21(1):164.