Continuous Glucose Monitor and Early Diabetes: Should You Use One?

If you’ve been diagnosed with early diabetes (prediabetes), or you have risk factors for Type 2 diabetes, you may be wondering whether a wearable continuous glucose monitor (CGM) is right for you. 

After all, there’s been a huge uptick in the use of this device in people without diabetes looking to optimize their health or lose weight. This is a trend that’s set to continue with the release of Dexcom Stelo in the summer of 2024, the first CGM available over the counter (OTC) in the U.S. So, could real-time data about your glucose levels help you prevent diabetes?    

Maybe. While research shows promising results with CGM use in Type 1 diabetes and Type 2 diabetes, there’s much less evidence about its benefits for people with prediabetes or those at risk for diabetes.

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Although CGMs may help connect the dots between lifestyle changes and glucose levels, this doesn’t translate to improved health for people without diabetes. In turn, experts are on the fence about their use in early diabetes. 

How do continuous glucose monitoring systems work?

A CGM is a wearable, glucose-tracking device. It measures glucose in the body’s (interstitial) fluid under the skin. When you wear a CGM, you can track your own glucose changes over time.

CGMs provide a “snapshot” of glucose readings as well as a “big picture” view of patterns and trends. Depending on the type of CGM, you can get glucose readings as often as every 1 to 5 minutes. 

With the Dexcom Stelo, you can get a real-time glucose level every 15 minutes. This happens in three steps:

1. A sensor picks up changes in glucose levels. 

2. A transmitter wirelessly shares glucose data.

3. A receiver (smartphone) collects and displays Stelo’s glucose data and trends.

Can you get a CGM over the counter with prediabetes?

The release of the Dexcom Stelo in the summer of 2024 marks the first time a CGM device is available without a prescription. No CGM devices were available OTC before then. But the fact that you can get this type of device OTC doesn't mean you should, though. More on that below. 

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The Dexcom Stelo is FDA-cleared for people who are:

• 18 years and older

• Not taking insulin

• Not at severe risk of low glucose (hypoglycemia)

While you can easily purchase and wear a Dexcom Stelo CGM, you’ll have to pay for it out of pocket. That’s because insurance plans don’t cover CGMs for people with prediabetes. If you have a high deductible health plan, using your health savings account (HSA) can help offset some of the cost. 

Potential benefits of CGM for prediabetes

About 98 million (or 1 in 3) adults in the U.S. have prediabetes — and 80% aren’t aware they have it. So, using CGM technology could be a game-changer. Tracking personal health data is a trendy way to optimize health — and CGMs are no exception. 

But are they worthwhile for people with prediabetes? That may vary from person to person. And it may differ depending on whether you know you have prediabetes, or not. 

Benefits of CGM for people who know they have prediabetes   

If you’re one of the 20% of people with early diabetes who know they have it, you may be determined to stop it in its tracks. 

And, real-time glucose monitoring with a wearable CGM may help to inform healthy lifestyle changes that could help prevent Type 2 diabetes. After all, evidence shows that when people develop prediabetes and make changes to their diet and exercise habits soon after, they’re able to delay or even prevent Type 2 diabetes.

Benefits of CGM for diagnosing prediabetes 

But what if you’re one of the 80% of people with prediabetes who don’t know they have it? Could a CGM help you identify prediabetes earlier? 

It’s possible. But here’s the thing: Glucose levels vary. A lot. And that’s normal. So wearing a CGM may help to pick up prediabetes, but it may also create a situation of “information overload and potential anxiety,” according to endocrinologist Sonal Chaudhry, MD. 

And, a CGM isn’t designed to diagnose diabetes or prediabetes. “CGMs are useful, but they’re not perfect,” said endocrinologist Minisha Sood, MD. 

In fact, Sood said, there’s an inherent inaccuracy in these devices. That’s because they measure glucose levels in the fluid under the skin, not glucose levels in the blood itself. So, while the snapshots and the trends they provide are useful, they shouldn’t take the place of “validated formal blood testing for the diagnosis of prediabetes.”  

Endocrinologist Farah Khan, MD, agreed. Khan pointed to the guidelines from the American Diabetes Association (ADA) for diagnosing diabetes and prediabetes. The best way to diagnose prediabetes is to get tested, with a blood test. “Prediabetes can only be diagnosed from an elevated A1C or fasting glucose levels”, Khan said. “Or, after a 2-hour oral glucose tolerance test.” 

This online test from the CDC can help you figure out if you need testing (with bloodwork). If you meet any of the following criteria, then reach out to your doctor’s office, health clinic, or local pharmacy to schedule a screening:   

• You’re 45 years or older.

• You have a body mass index (BMI) of 25 or higher.

• You have high blood pressure.

• You exercise fewer than three times a week.

• You have a parent or sibling who has Type 2 diabetes.

• You’re African American, Hispanic/Latino, American Indian, Asian American, or Pacific Islander. 

• You have polycystic ovary syndrome (PCOS) or diabetes during pregnancy. 

Can you use continuous glucose monitoring to reverse prediabetes?

Maybe. But before CGM devices are recommended widely to help reverse or treat prediabetes, we need to know more. So far, their effectiveness hasn’t been proven. Four physicians were interviewed for this article, and they’re on the fence. 

“There are no trials that have tested the benefits of CGMs in people who don’t have diabetes,” said Sanjai Sinha, MD. This includes people who have prediabetes. He pointed to a review study of the use of CGM in people with prediabetes. It’s possible that using a CGM may help with the lifestyle changes needed to reduce the need for treatment in people with prediabetes. Specifically, in helping people see for themselves how what they eat and how much they exercise can affect their glucose levels. 

“In people with prediabetes who struggle to make lifestyle changes, using a CGM short-term may help,” Sood said. “In some people, the CGM data can help make connections between the food they eat, their exercise levels, and their sugar levels." 

Chaudhry echoed this, and added: “There are some important things to be aware of: Glucose levels measured by CGM lag behind true blood glucose levels. This means CGM data won't be accurate if your glucose levels are changing rapidly.”

“CGM reading is still not as accurate as a finger-stick glucose test,” Chaudhry said.

Using a CGM is not without drawbacks and risks. It’s expensive, can provide an overload of information, and be a possible trigger for anxiety and obsessive and disordered eating. 

Why trust our experts?

Written by:

Jewels Doskicz, RN, BA

Jewels Doskicz, RN, BA, is an Arizona-based registered nurse with 22 years of hospital-wide clinical nursing experience and 11 years of medical writing and editing experience. She was a former healthcare content creator for a digital health tool at HealthLoop and director of clinical content operations at GetWellNetwork.

Edited by:

Sophie Vergnaud, MD

Sophie Vergnaud, MD, is the Senior Medical Director for GoodRx Health. An experienced and dedicated pulmonologist and hospitalist, she spent a decade practicing and teaching clinical medicine at academic hospitals throughout London before transitioning to a career in health education and health technology.

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