Are Glucose Monitors Useful for People Who Don’t Have Diabetes?

Daily finger-pricks to measure blood glucose were once a necessary norm for people with diabetes who use insulin—providing information essential to making real-time decisions about insulin use, food, and activity. 

But since 1999, continuous glucose monitors (CGMs) have revolutionized how people with diabetes manage the disease. The small wearable skin sensors track glucose levels every minute or every few minutes, making it possible to measure blood sugar in real time without drawing blood.   

Since the FDA approved the first over-the-counter continuous glucose monitors last year, they’ve become a growing wellness trend among people without diabetes. Users are drawn to claims that tracking glucose levels can help them lose weight, improve metabolic health, and prevent disease by better understanding how food, exercise, and stress affect their blood sugar levels. 

For those who don’t use insulin, can hacking blood sugar lead to better health? Experts say the evidence is scant—and it’s unclear what CGM data can tell people without diabetes about their overall health. 

How does blood sugar affect the body?  

When we eat, blood glucose—the body’s main source of energy—rises. High-carbohydrate foods—like fruit, processed snacks, and even milk and some beans—will cause glucose spikes. While what we eat is the key factor in blood sugar levels, it’s not just foods that impact blood sugar: Stress, skipping meals, lack of physical activity, and hormonal changes can all lead to increases.  

In the short term, these spikes—and subsequent dips as blood glucose returns to normal levels—can cause fatigue and brain fog. Long term, frequent and significant blood sugar spikes can contribute to a range of health issues including insulin resistance, type 2 diabetes, weight gain, and kidney and heart disease.   

But high glucose levels are usually asymptomatic, and it’s unclear whether CGM readings are a reliable predictor of long-term disease risk in people who do not use insulin. 

“If you have prediabetes, the only way to find out is to get screened” using lab tests, says diabetes researcher Elizabeth Selvin, PhD ’04, MPH, a professor in Epidemiology. “Regular screening using lab tests such as glucose and HbA1c is still the best way to understand risk.”  

How do CGMs work? 

Continuous glucose monitors are small sensors worn on the skin, usually on the abdomen or the back of the arm, that track blood glucose levels and send real-time information to an accompanying app.  

The devices allow users to see how food, exercise, and stress affect glucose levels—even if they don’t feel symptoms of abnormal glucose levels. For people with diabetes who use insulin, CGMs are nothing short of “lifesaving, revolutionary devices that prevent hypoglycemia (low blood sugar) and help improve glucose control by assisting with precise dosing of insulin, meal adjustments, and monitoring to keep physical activity safe,” says Selvin. 

They provide “safer and better blood sugar management, all while being much more convenient,” says Michael Fang, PhD, MHS ’21, an assistant professor in Epidemiology, whose work focuses on diabetes and wearable technologies. 

For people who don’t use insulin, the benefits are far from clear.  

“In people without diabetes, we don’t really know how to act on differing glucose patterns,” says Fang. “All the clinical information about how to interpret and act on the information from CGMs is for people with diabetes.”   

It is likely that a healthy person may regularly have some glucose spikes—and tracking those too closely can cause unnecessary anxiety about occasional “high” readings, says Selvin. “We don’t actually know that monitoring or manipulating CGM glucose levels in people without diabetes can improve health.” 

Can CGMs help people make healthier choices and lose weight? 

Potentially. Being aware of whether a bagel or bran flakes caused a blood sugar spike could motivate someone to choose healthier foods or prioritize exercise, which lowers blood sugar. These choices could, in turn, lower a person’s risk of developing chronic diseases—including diabetes—and help with weight management.  

“But it’s not a given,” says Selvin.   

“No major clinical trials have attempted to demonstrate these types of benefits,” says Fang. While some small trials have shown short-term benefits for people without diabetes using CGMs, “I think we do need more definitive trial data,” he says. 

What are the potential risks?  

CGMs only measure glucose, and if users focus too much on those readings, they may ignore factors that are just as, if not more, important, including cholesterol, triglycerides, and sodium intake.  

Improving metabolic health—which consumer CGMs purport to do—is much more complicated than simply avoiding foods that trigger glucose spikes, Selvin says. “For example, if you substitute a high-salt, high saturated-fat food like a sausage for an orange at breakfast, your glucose may not rise as much, but that is not necessarily a good trade-off.” 

What should people without diabetes watch out for if they’re considering trying the devices? 

First, you don’t need to wear it all the time. “For someone without diabetes, maybe letting people wear the sensors once or twice is enough. After they learn about what foods do to their glucose levels, they’ll know how to adjust their behaviors to minimize glucose spikes,” says Fang. There are other ways to do this that don’t require a device or an app—such as fasting glucose tests done at doctors’ offices, which are used to diagnose prediabetes and diabetes. “These measurements are one-time tests. But even these can be useful helping guide diet and physical activity changes,” says Fang. 

The devices are available, and they’re popular—but the rise of consumer CGMs is currently a case of tech and consumer demand outpacing research, says Fang. The FDA approval allowed the devices to be sold without a prescription and marketed as consumer devices, but “whether they actually improved health outcomes was not a factor in the FDA’s decision,” he says.