CGMs (Continuous Glucose Monitors) are devices that measure blood glucose on a continuous basis using a sensor device placed in the interstitial space using an enzymatic technology which reacts with glucose molecules, generating an electric current proportional to glucose concentration. Because it takes time for blood glucose to travel from the blood stream to the interstitial fluid, there is an inherent lag time of 5-20 minutes between actual blood glucose and the level measured by the CGM.

Since being introduced in 1999, the devices have rapidly improved with most devices today no longer requiring calibration with fingerstick glucose measurements. Most people with type 1 diabetes in this country are managed by endocrinologists who now exclusively use CGMs for glycemic management decisions. These patients are at considerable risk for serious hypoglycemia. CGMs have significantly reduced this risk while achieving improved glycemic control. This mainstream use requires involvement not only of parents but also school systems. This year, my daughter, who teaches fourth grade, was trained to service a CGM device for a student in her classroom.

Most of our rehab and long-stay patients have Type 2 diabetes. Medicare and most insurance payers have approved the use of CGMs for type 2 patients who are insulin dependent or have a history of serious hypoglycemia on oral meds. In this patient population, the literature documents improved A1-C levels and patients seem to be more compliant with following a healthy lifestyle because they can now get real time feedback on the effect of exercise and foods on their glycemic control. The value for avoiding hypoglycemia has been mixed to date.

Earlier this year, I gained experience with two of the more popular devices in the USA while serving as the interim medical director for a PACE program while their director was on birth-related leave. I found both devices (Freestyle Libre & Clarity Decom series) easy to initiate in our clinic with subsequent reports providing valuable information for making clinical decisions. These devices typically report an AGP (Ambulatory Glucose Profile) that is one page that includes a visual scale of Time in Range – 70-180 - (as well as Above and Below), measures of average glucose, glucose management indicator, glucose variability, and then 14 day scale of glucose profile and daily scale of glucose profile.

This information helped our team design diabetes care changes that addressed the specific problems identified in the AGP report.

In the PA-LTC setting, many of our people with diabetes have comorbidities that shorten the life span of red cells which adversely impacts the reliability of A1C measurements. In addition, some are at substantial risk for serious hypoglycemia due to dementia, CKD, and hypoglycemic unawareness. These devices are well tolerated in this patient population and even if only used for several weeks at a time, could adjust their glycemic care to a safer regimen.

For our rehab patients the use of these devices in the outpatient setting by PCPs is growing with huge patient demand, particularly in the obese population on weekly GLP-1 or GIP-GLP-1 receptor agonists. I predict that these patients will demand that we use their devices for monitoring their glycemic control.

While this may seem overwhelming, my experience at PACE with their implementation and use was very favorable. I encourage medical directors to step into the water and assist their facilities to develop CGM use programs. Here are some helpful links for the two most used devices and other pertinent resources:

1. FreeStyle Libre Systems (CGM) – For Healthcare Professionals
2. Clarity Professional – Diabetes Clinic Management Software 
3. Welcome to Dexcom Clarity for Healthcare Professionals. 
4. 2024 ADA Standards of Care Slide Deck (Slides 100-102 display the value and reporting of CGMs.)
5. Wikipedia re CGMs

I began my career in medicine in the 1970’s where we used blood glucose and urine S&As for glycemic management. Then in the mid 1980’s finger stick blood glucose monitoring arrived which rapidly replaced urine S&As. Then, A1C’s arrived and became the new goal for glycemic control. The role of CGMs in the care of persons with type 2 diabetes is still in development. Based on my experience with glycemic technologies, I predict this will soon become mainstream.