Continuous glucose monitors (CGM) provide a state-of-the-art tool for monitoring and responding to glucose levels. Because of this, CGM has the potential to improve the health and well-being of anyone living with diabetes, regardless of type.
Some argue that CGM’s cost and effectiveness, as demonstrated in scientific studies, only justify its use by people with type 1 diabetes (T1D) or insulin-using type 2 diabetes (T2D).
But to say that CGM is only useful for dosing insulin and therefore should be limited to insulin users, takes a very narrow view of this technology and its potential benefits for all people living with diabetes.
Let’s first clarify what CGM is, and what it provides.
CGM is a personal medical device. It’s made up of a sensor that’s physically attached to your body and a scanner (or smart phone app) that captures glucose level readings from the sensor. The readings are captured at approximately 5-minute intervals round the clock. CGM replaces the glucometer, which requires a fingerstick (using expensive test strips) to draw blood each time a reading is taken.
CGM captures and stores the data from all the readings it takes. Through software, it reports your current glucose level and indicates whether it is trending down (toward hypoglycemia) or up (toward hyperglycemia).
Because a CGM captures so many readings throughout the day, its software can also plot changes in glucose levels with much more accuracy than what’s captured using a traditional glucometer. This rich data set also lends itself to reporting more detailed and nuanced visualizations of your glucose levels over time.
One such visualization is Time in Range (TIR) a measure of how much time throughout the day you stay within a target glucose range of 70 to 180 mg/dL (3.9 to 10 mmol/l). Staying within this range is characterized as good glycemic management or “tight control,” and is recognized as minimizing the risk of developing complications or diabetes progressing.
The traditional glucose monitoring tools available to people with diabetes (PWDs), including the glucometer and the A1C test, cannot come close to providing the same level of detailed, contextualized, or real-time glucose readings as the CGM.
The A1C test, which provides an indication of glucose levels in a 3-month period, has been recognized as the gold standard for measuring glucose management. But it has serious limitations.
The A1C result is based on a calculated average. That means a “good” A1C result (of 7 percent or below) may be indicating a middle point between severe swings in glucose levels averaged out over 3 months. Or the same result might be indicating 3 months of steady glucose levels that fall within a tight range. There’s no way to tell the difference. That’s why more healthcare professionals and PWDs are relying on TIR as a much more accurate and informative measure.
And CGM is the perfect tool to track TIR.
For people with T2D, the traditional minimum standard of care was to check glucose levels once a day with a fingerstick meter, usually upon waking. This practice gave a single point of data and no insight into glucose levels experienced throughout the rest of the day.
Switching to a CGM could be nothing short of revolutionary for those PWDs.
Yet, we must also remember that CGM, like any digital health device, is a tool and not a panacea.
While CGM can capture, analyze, and report glucose level data in a much more complete manner than the traditional glucometer readings or A1C results, PWDs can only benefit from this if they understand what the data represents and the various ways they can respond to actively manage their glucose levels.
Training and coaching are needed to help people get the most out of their CGM and better manage their diabetes.
We talked with Julia Blanchette, a registered nurse, and diabetes care and education specialist (DCES), about her experience helping people who live with T2D learn to use CGM. She is also currently a postdoctoral fellow in integrated diabetes management at the University of Utah College of Nursing. She estimates that she’s coached more than a dozen people with T2D on how to use CGM effectively in their diabetes management.
“I’ve had clients with T2D who don’t use insulin use CGM,” Blanchette says. “Usually they pay out of pocket for Abbott FreeStyle Libre and they like it because they learn about how different foods and activities impact BG (blood glucose).”
She believes it’s critical for PWDs to have healthcare professionals who are willing and able to help them make the most of CGM.
“To be successful in learning about how different factors impact BG through the real-time data, one has to have a doctor who will review and discuss what the data means, and teach the person with diabetes how to understand the data,” she says.
So, what exactly should you be doing with your CGM data?
CGM provides nearly real-time biofeedback — which makes the biofeedback actionable. Using CGM, you can see immediate results of any action taken, whether it be exercise, choosing a lower carb meal, or dosing insulin.
By learning how to interpret the glucose readings captured and plotted by the CGM, PWDs can understand the relationship between the many factors that affect glucose levels. Some factors might include food eaten, exercise, stress, illness, menstruation, lack of sleep, etc.
Over time, you can develop an awareness from the immediate feedback you receive on the effects of your self-care. This awareness can help motivate and inform behavioral changes that affect BG levels. These changes may have a positive impact on quality of life and ultimately, may reduce the likelihood of developing complications from diabetes.
It’s these kinds of behavioral changes that Blanchette says illustrate success that she’s seen with her clients using a CGM.
“Success in this context is making behavior changes after learning from the real-time data. Examples of these changes could be eating an egg with oatmeal for breakfast to lower a BG spike, staying active to lower BG trends, or strategizing ways to reduce stress and relax a bit at work.”
Despite reports from the field like Blanchette’s, arguments against people with T2D using CGM still exist. Two points that are most often cited focus on cost and the lack of definitive studies that confirm the benefits of CGM use.
First, there’s the claim that CGM is not cost-effective for people with T2D who don’t use insulin. This is, at best, based on an apples-to-oranges comparison. Some information below attempts to compare the cost of using a glucometer against the cost of using a CGM.
The estimated costs of CGM versus glucometer and test strip use are based on manufacturer suggested retail prices. But no one actually pays these prices in the United States. The actual dollar cost is nearly impossible to document because it varies so widely. Insurance companies negotiate their own individualized pricing with manufacturers and suppliers. And their members’ actual out-of-pocket costs depend on their individual health plans, which can also vary widely.
Also, the “not cost-effective” argument focuses solely on the dollar cost associated with using the medical devices, like glucometers and CGM. It doesn’t consider any potential savings in overall healthcare costs from reduced hypoglycemic emergencies in the short term or fewer complications in the long term. That’s where the real impact and the real money lies.
No clear, definitive study results
The second argument says that there are currently no long-term studies that document the benefits of CGM use by people with T2D. So, any evidence presented should be viewed as anecdotal and therefore, inconclusive.
For example, Dr. Katrina Donahue, director of research at the University of North Carolina Department of Family Medicine, and co-author of a
“I don’t see the extra value with CGM in this population with the current evidence we have,” Donahue tells Kaiser Health News. “I’m not sure if more technology is the right answer for most people with T2D.”
But it’s important to note that CGM is still relatively new, and hasn’t had the chance yet to show its full potential for a broader population. CGM was approved for use in the United States in 1999.
Almost all the data on outcomes in its first decade-plus came from short-term studies of people with T1D who took insulin regularly. There are few studies on CGM use among non-insulin-dependent PWDs overall, and certainly not long-term.
For one thing, long-term studies can be tricky on medical technology that changes and evolves quickly. The first CGM approved for use required a visit to the doctor’s office to have its data manually downloaded and reviewed. Today’s CGM technology makes its data available instantaneously via an app on the user’s smart phone.
Some of today’s CGMs integrate with insulin pumps providing an automated system for insulin dosing, sometimes referred to as looping — a capability that was scarcely imagined in 1999. These developments may render any study results irrelevant based on earlier models of CGM.
In other words, in today’s highly dynamic technological environment, traditional multi-year studies may no longer make sense. By the time the results are known and reported, the specific CGM device tested in this manner will likely be replaced by something with different capabilities. New approaches to research are needed, as noted by the authors of this
The authors also note how creators of new medical technologies “face significant challenges to overcome the ‘no evidence, no implementation — no implementation, no evidence’ paradox in digital health.”
The other concern is immediacy. For people who take insulin and are at more immediate risk of developing hypoglycemia, it’s easier to track and showcase the benefits of CGM. For T2Ds, on the other hand, the benefits are more incremental and less dramatic — but that doesn’t mean they aren’t significant.
Diabetes is a condition that can progress slowly, taking decades for complications to appear. It’s unlikely that any research study can draw a direct line between the use of a particular treatment approach or medical device and the absence of specific negative outcomes among PWDs.
Some doctors in this 2020 research review, claim that “most people with type 2 diabetes do not require self-monitoring of blood glucose, and unnecessary monitoring not only wastes money but can negatively impact quality of life.”
That’s a bold leap to make, and many people with T2D would strongly disagree.
Until scientific research practices find a way to address these limitations, reports from PWDs in the field are going to be the key evidence available to us. Thankfully, there is increasing use of patient-reported outcomes (PROs) in clinical trials to assess the impact of medical treatments and interventions.
Clearly, the more broadly CGM is used, the more information we will have on long-term benefits.
Aside from the spurious arguments against expanding access to CGM, there are some important structural barriers that exist.
Lack of insurance coverage
Starting in 2017, Medicare covered the costs associated with CGM. Only after reclassifying the CGM as therapeutic and not just “precautionary” did Medicare start covering part of the cost of CGM use. Private healthcare insurance providers followed Medicare’s lead, adding or expanding their CGM coverage for health plan members.
But CGM still remains out of reach to many PWDs of any type due to limited or no insurance coverage for the ongoing costs.
The most direct way to address this barrier is for manufacturers to reduce the out-of-pocket costs of the device and sensors or to lobby harder for healthcare insurance to cover more direct costs.
Stringent requirements for coverage approval
Even with some expansion of coverage, receiving approval for insurance coverage still presents hurdles in a huge number of cases.
The criteria to receive approval under Medicare, for instance, is quite specific. It includes, among other things, requirements that PWDs:
- check glucose levels four or more times each day
- use insulin
- give three or more insulin injections each day, or uses an insulin infusion pump
- regularly adjust their insulin regimen to keep glucose levels in check
- complete an in-person appointment with the prescribing doctor
Clearly, this criteria excludes anyone not using insulin to manage their diabetes. Private health insurance companies use similar criteria when approving CGM coverage for their members.
To expand access to CGM, these rules need to open up so that people using insulin are not the only people eligible.
We asked Dr. Blanchette what motivates her T2D clients to make the extra effort often required to get access to CGM.
“The (people) who are really engaged in problem-solving and really want to understand how to better manage blood glucose from the real-time data are the most motivated,” she says. “Also, sometimes they (are motivated by) the idea of no fingersticks and the continuous data. Others have had the opportunity to sample CGM through their diabetes healthcare professionals and liked it enough to want to keep using it.”
This begs the question: How can some healthcare professionals claim that there is no quality of life or a negative quality of life outcome with CGM when so many T2Ds haven’t yet been given the opportunity to use one?
Naturally, CGM may not be useful for *everyone* living with diabetes. Effective use comes with a substantial learning curve and dollar costs.
But shouldn’t the decision to at least try a CGM — maybe the most powerful glucose monitoring tool available — lie with the PWDs and their healthcare professionals?
Corinna Cornejo is a Hawaii-based content writer and diabetes advocate. Her aim is to help people make better informed decisions about their health and healthcare. As a Latina diagnosed with type 2 diabetes in 2009, she understands first-hand the many challenges life with diabetes presents. You can find her thoughts and musings about life with T2D on Twitter at @type2musings.