No More Finger Sticks: Continuous Glucose Monitors

Nancy Sidhom MSN, ANP-BC, CDCES

Have you ever tried to do something in the dark? no matter how simple the task, you quickly find it is nearly impossible until someone turns on the light. Continuous glucose monitor, or CGM, therapy is nothing less than that light switch for so many blindly grappling through their diabetes management.

Why is CGM such a game changer? Historically, we have asked patients to manage their blood sugar value, which in truth is an ever-changing number they simply cannot see. On a very basic level, it’s akin to asking someone to abide by the speed limit in a car without a speedometer. Despite the availability of fingerstick testing, it essentially provides patients limited information from single moments in time rather than the big picture they need to see. Fingerstick tests are like the few pictures you snapped on your fishing trip while CGM sensor technology is the drone video footage of your day.

From a nursing perspective, education is the center point of every patient encounter. Many concepts can be difficult to understand including glycemic index, post prandial blood sugar spikes and insulin action times. CGM allows patients to watch these difficult concepts play out in real time, usually on an app conveniently available on their phones. The continuous streaming of blood glucose data allows for a much greater understanding of blood glucose trends, cause and effect, and it allows individuals to make more informed treatment decisions throughout the day to finally reach their goal. When a patient can visualize the effects of dietary choices or exercise on their blood sugars, it acts as a powerful form of biofeedback. CGM use has led many patients to reduce insulin use, revamp dietary choices, create exercise habits and effectively instill long-sought behavior change.

Historically, CGM therapy was reserved for patients with Type 1 diabetes. Fortunately, CGM therapy is now widely covered for patients with Type 1 and Type 2 diabetes. Medicare and MassHealth cover CGM therapy for most patients on more than three insulin injections per day who must adjust insulin intake based on blood glucose data. Many commercial insurance providers cover CGM therapy for patients with diabetes regardless of insulin use.

Currently, there are several CGM sensors available for personal use which are FDA approved for treatment decisions without additional fingerstick testing: Dexcom, Abbott Freestyle Libre and Senseonics Eversense.

The Dexcom G6 sensor allows for 10 days of continuous wear. The sensor continuously updates blood glucose data to an app/smartwatch/receiver every five minutes. Blood sugars are displayed with an arrow indicating the direction they are trending along with a graph of blood sugars. The sensor offers customizable high and low alerts but has one low alert at 55 mg/dl that cannot be switched off.

Freestyle Libre sensor allows for 14 days of continuous wear. Abbott Freestyle currently has two sensors on the market, the Libre and Libre 2. The main difference between the two sensors is the alarm option. The original Libre does not have any low- or high-glucose alert features. The Libre 2 offers customizable high and low alarms. Both the Libre and Libre 2 are flash CGM sensors meaning the data is not continuously sent to the reader or their phone, but rather the patient must scan the sensor with the reader or smartphone to view a blood glucose reading along with the blood sugar trend and graph.

The Eversense CGM sensor from Senseonics is the first longterm implantable sensor. The sensor is generally inserted under the bicep muscle and replaced every 90 days at an outpatient visit. Advantages of the implantable sensor include 90 days of continuous wear and the ability to remove the external transmitter without needing to change the sensor.

Several studies have demonstrated that use of CGM therapy significantly lowers HbA1c (1,2). Data from 248 patients — 182 with Type 1 diabetes and 66 with Type 2 diabetes — demonstrated a significant decrease in mean HbA1c from 8.2% at baseline to 7.1% at the end of the three-month study (P < 0.001). More than half of those with initial HbA1c values >7% experienced absolute HbA1c reductions of >1%. Additionally, significant reductions in diabetes distress and hypoglycemic concerns were observed (P < 0.001) (1).

Few things are truly as rewarding as the improvement in self-management seen after prescribing CGM therapy. In my experience, it is not unusual for patients who have struggled for years with uncontrolled sugars, many with HbA1c values > 10%, to return to the office two weeks after sensor placement with near normal glucose control. I recently asked one of those patients why CGM made the difference for her. She admitted, as a mother of five children, it couldn’t be easier for her to forget to care for herself, which included the arduous task of trying to measure her blood sugars and remember to take her medications. While wearing the CGM sensor, however, she simply couldn’t ignore the high blood sugars. It directly correlated to marked improvements in medication compliance and diet.

Diabetes is a chronic complex condition associated with a long list of complications and a high treatment burden. Fortunately, this technology offers patients a non-pharmacological tool to proactively address their glucose level and improve overall glucose control thus reducing their risk of long- term complications while improving their day-to-day quality of life.

References:

1. WH;, Gilbert TR;Noar A;Blalock O;Polonsky. “Change in Hemoglobin A1C and Quality of Life with Real-Time Continuous Glucose Monitoring Use by People with Insulin-Treated Diabetes in the Landmark Study.” Diabetes Technology &amp; Therapeutics, U.S. National Library of Medicine, pubmed.ncbi.nlm.nih. gov/33470882/.

2. Wright, Eugene E., et al. Use of Flash Continuous Glucose Monitoring Is Associated With A1C Reduction in People with Type 2 DIABETES Treated with Basal Insulin or Noninsulin Therapy. Diabetes Spectrum, American Diabetes Association, 1 May 2021, spectrum.diabetesjournals.org/content/34/2/184.