Who Should Use a Continuous Glucose Monitor?

Historically, checking your blood glucose (sugar) levels meant pricking your finger with a needle and dropping blood onto a test strip. A person with diabetes might have had to do this multiple times a day, as the disease can cause blood glucose levels to be too high, which can be dangerous in many different ways.

But with the advent of continuous glucose monitors (CGMs) in the late 1990s, sticking your finger with a needle has become less common. A CGM is a wearable medical device that works by having a small, removable sensor (placed just under the skin) measure glucose levels in real time and send alerts when they are outside a target range.

Initially, CGMs were prescription-only and reserved for people with type 1 diabetes, a condition in which the body does not make insulin, the vital hormone that moves glucose from the blood to the cells, where its energy can be used for various functions. But over the years, as the number of people with type 2 diabetes (in which the body makes less insulin than is needed or has built up a resistance to it) has gone up, insurance coverage has expanded, and those with type 2 diabetes who require insulin therapy are increasingly given a prescription for a CGM.

However, that left people with type 2 diabetes who do not take insulin or those who have prediabetes (when blood sugar levels are higher than normal but not high enough to be diagnosed with type 2 diabetes) with the finger-stick option as the only way to monitor their blood glucose levels.

That changed this past spring when the Food and Drug Administration (FDA) approved the first over-the-counter (OTC) CGM. This new CGM, called the Dexcom Stelo Glucose Biosensor System, is meant for people 18 and up who have type 2 diabetes (but do not take insulin) or prediabetes. (The Stelo system is not for those with hypoglycemia, a condition marked by low blood sugar.)

The OTC Stelo CGM is essentially the same—in terms of offerings and accuracy—as a prescription-based one, which is also sold by Dexcom. And as with prescription CGMs, users can sync OTC versions with their smartphones to receive readings.

Monitoring blood glucose levels is crucial for an individual with diabetes because over time, high levels can permanently damage the eyes, nerves, kidneys, blood vessels, and other parts of the body. With a CGM, a person can adjust their diet, medication, and activity levels to prevent dangerous spikes or drops in their blood sugar.

Since the approval of the Stelo system, other CGMs, including the Abbott Libre Rio system, have received approval to be sold over the counter.

Below, we talk with Patricia Peter, MD, a Yale Medicine endocrinologist, about who should consider using an OTC continuous glucose monitor.

According to Dr. Peter, being able to buy a CGM over the counter without a prescription is helpful to many people with prediabetes and those with type 2 diabetes who manage the disease with medications other than insulin, such as GLP-1 agonists like semaglutide (brand name Ozempic®). It’s also a welcome option for people who don’t like needles.

“Finger sticks are uncomfortable, as the fingertips are really sensitive,” Dr. Peter says. “They are also inconvenient, especially if an individual is at work and has to go through the process of pricking their finger, making sure they have a clean spot to do it, finding the time to do it, and finding the privacy to do it. It's very difficult.”

CGMs are designed to monitor blood sugar levels—not to deliver insulin. Insulin delivery is typically managed through separate devices, such as insulin pumps, injections, or pens.

However, some advanced diabetes management systems integrate CGMs with insulin pumps, using the data from the CGM to automatically adjust insulin delivery based on glucose readings, which helps to keep blood sugar levels within a target range.

Type 2 diabetes is primarily characterized by insulin resistance. Initially, the body often produces enough insulin, but the cells do not respond to it effectively. As a result, treatments may be focused less on insulin therapy and more on lifestyle modifications, including diet and exercise (which can improve insulin sensitivity and help control glucose levels), as well as oral or injectable medications that improve insulin sensitivity.

By regularly monitoring their blood glucose levels and making necessary adjustments to their diet, exercise, and medication regimen, some people can maintain control of their diabetes without needing insulin.

Diet is important for controlling blood sugar levels. Carbohydrates affect blood sugar directly since they turn into glucose. As a result, managing how much and what type of carbs you eat can help keep levels steady. For example, eating "low-glycemic" foods, like whole grains and vegetables, is important because they are digested slowly and raise blood sugar gradually as opposed to "high-glycemic" foods, such as white rice and sugary snacks, which cause blood sugar levels to spike.

Exercise helps manage blood sugar by making your body more sensitive to insulin, which allows cells to use glucose better. It can also lead to weight loss, which decreases insulin resistance. Plus, physical activity uses glucose for energy, lowering blood sugar levels and reducing stress, which can otherwise raise blood sugar. Regular exercise contributes to overall better health and more stable blood sugar levels over time.

The idea behind a person with type 2 diabetes using a CGM is that they could make real-time changes to their diet and exercise routine based on readings before and after meals.

The cost of Stelo might be prohibitive as insurance carriers do not currently cover it (although it is FSA/HSA eligible, according to the company's website). A Stelo device is $99 and comes with two sensors, each of which can be worn for up to 15 days.

Dr. Peter says some of her patients already pay out of pocket for continuous glucose monitors because they find it helpful to have immediate feedback on how the food they eat impacts their blood sugar levels. “It motivates people to see how food, exercise, and beverages can affect them in real time,” she says.

If cost is an issue, Dr. Peter says that intermittent glucose monitoring could be worth pursuing.

“If you’re unable to afford checking your blood sugar for the entire month, you could instead check it for at least two weeks of the month to get a sense of your levels,” she says. “Then, you can use that information to get yourself back on track, in terms of diet and exercise, and you could go back to checking with finger sticks until the start of the next month. This is especially true if you have type 2 diabetes—as opposed to prediabetes, which could require less monitoring.”

With that in mind, it’s possible to see how intermittent continuous glucose monitoring could be helpful, she adds.

People without a condition who are simply worried about their blood sugar levels might be interested in the Stelo system, Dr. Peter notes.

“If you have a family history of diabetes, for instance, and want to decrease your long-term risk, it might be helpful to track your blood sugar levels,” she says. “The same might be true for women who have had gestational diabetes and needed insulin during their pregnancy. Although many women with gestational diabetes do not need any treatment after delivery, they still are at higher risk for developing diabetes.”

However, for a healthy person who has no risk factors for diabetes but just likes to keep track of health metrics, Dr. Peter questions the benefit of a CGM.

“I’m not sure what people would do with that kind of information,” she says. “It could be easy to overreact if you don’t have the context for what these numbers mean, so it would be important to have a medical professional help you interpret that data instead of doing it yourself.”

Ultimately, Dr. Peter suggests that anyone interested in a CGM talk to their medical provider first.