Are Continuous Glucose Monitors Worth It for Non-Diabetics? The Research Says No, and the FDA Never Asked

A 972-patient Mass General Brigham study published in October 2025 found CGM metrics barely associate with HbA1c in people with normal blood sugar (β = 0.10). The wellness industry sold a $1,200-per-year subscription to fix a problem most users do not have.

The pitch from Dexcom Stelo and Abbott Lingo is straightforward and seductive: a small sensor on your arm reveals what your meals are doing to your metabolism, and that data is the foundation of optimized energy, weight, and longevity. Whether continuous glucose monitors are worth it for non-diabetics depends on whether that pitch survives the published research, the accuracy data, and a comparison to what an annual hemoglobin A1c blood test costs at the same Walgreens. It does not. The Mass General Brigham team behind the 972-patient 2025 study on this question concluded that for people with normal or prediabetic blood sugar, the numbers a CGM streams to your phone are not a substitute for the test that actually predicts diabetes risk.

The Mass General Brigham study found the data does not work for healthy people

In October 2025, Dr. Jorge Rodriguez and colleagues at Mass General Brigham published a study in Diabetes Technology and Therapeutics analyzing 972 adults aged 40 to 85 across three glycemic groups: 421 with type 2 diabetes, 319 with prediabetes, and 232 with normal blood sugar. They tested whether eight different CGM metrics tracked the standard HbA1c lab test. In the type 2 diabetes group, mean glucose tracked HbA1c with a strong standardized beta of 0.79. In the prediabetes group, the association attenuated to 0.22. In the normoglycemia group, the standardized beta dropped to 0.10. Functionally zero.

Rodriguez summarized the finding in plain language. CGMs are great tools for people with diabetes. Their numbers do not reflect the standard HbA1c test for people with prediabetes or normal blood sugar. He added that for those without diabetes, CGM data is not a substitute for HbA1c, which assesses blood sugar control over multiple months. That is the test endocrinologists use to screen for and diagnose diabetes. It is the test the American Diabetes Association recommends every three years for adults over 35. It is also a test you can buy directly from Quest or Labcorp for somewhere between thirty-eight and seventy-five dollars cash.

The FDA never asked whether they actually help anyone

Stelo received FDA clearance for over-the-counter sale in March 2024 and launched at retail that August. Lingo followed in June 2024. Both clearances were based on device safety, not on evidence the products improve health in non-diabetic users. Dr. Michael Fang, an assistant professor of epidemiology at Johns Hopkins Bloomberg School of Public Health, said the quiet part loud in a piece the school published in January 2026. Whether the devices actually improved health outcomes was not a factor in the FDA's decision. The framing matters because the marketing implies clinical legitimacy that the regulatory record does not actually support.

Dr. Priyanka Majety, an endocrinologist at VCU Health who treats diabetic patients, was blunt about it. Doctors and health care providers do not regularly use CGMs for people without metabolic health issues because there is not enough evidence yet to show that it is effective or appropriate for improving their health. Harvard Health takes the same position. CGMs cost several thousand dollars a year, insurers will not cover them for wellness use, and the bar for that to change is compelling evidence that they are actually helpful. That evidence does not exist.

OTC CGMs are not held to the same accuracy standards as the prescription versions

The accuracy gap is the part the marketing copy omits. A CNN review in March 2026 ran a side-by-side test with a reviewer wearing both Stelo and Lingo simultaneously. The two devices, made by competitors using similar interstitial fluid sensing technology, registered glucose readings 3 to 10 mg/dL apart on the same person at the same moment. Registered dietitian Ayla Barmmer flagged the reason. The FDA requires prescription CGMs made for diabetics to meet specific accuracy standards. Over-the-counter devices made for people without diabetes are not held to those same clinical accuracy standards.

Stelo claims roughly 8.3 percent MARD (Mean Absolute Relative Difference) and Lingo around 9.3 percent. Translation: at a real glucose value of 100 mg/dL, Stelo readings will average 8 to 9 mg/dL off in either direction, and Lingo readings will average 9 to 10 mg/dL off. For a diabetic taking insulin, that level of drift gets calibrated against fingerstick checks and clinical context. For a healthy person posting their breakfast oatmeal spike to Instagram, it is decimal-point theater. A 2023 review in the Journal of Diabetes Science and Technology was direct about a related problem: there are no consensus standards for what counts as an abnormal CGM value in non-diabetics or how to respond to one.

The peak performance glucose narrative does not have research behind it

The wellness story for CGMs hinges on the idea that maintaining a tight, narrow glucose range improves cognitive performance, prevents fatigue, and reduces long-term diabetes risk. The same review put it about as plainly as a peer-reviewed paper can. Some clinicians have promoted the idea that there is a glucose range where the body functions at peak performance. There is virtually no evidence for this belief. The reason there is no evidence is not that nobody looked. It is that the underlying premise treats normal post-meal glucose variation as a problem to fix, when in healthy bodies it is the exact response the system is designed to produce.

A diaTribe reviewer without diabetes wore a Stelo and described what happens when you give a healthy person a real-time data stream of a tightly regulated physiological process. She got anxious every time the number moved, started over-interpreting normal variation, and ended up worrying about whether her body was healthy when nothing was actually wrong with it. Her pancreas was working perfectly. The device was giving her something to worry about that did not exist before she was wearing it.

When a CGM actually makes sense

Short-term educational use, two to four weeks at most, can help certain populations. People with a confirmed prediabetes diagnosis, a strong family history of type 2 diabetes, prior gestational diabetes, polycystic ovary syndrome, insulin resistance, or elevated triglycerides have a real reason to see how their meals affect their glucose. Done with a clinician, paired with baseline lab work, and treated as a learning tool rather than a permanent biofeedback subscription, it can shift habits in a useful direction. That is not what Stelo and Lingo are selling, which is monthly recurring revenue. If lab work shows elevated A1c or fasting glucose and the conversation moves toward medication, our breakdown of berberine versus metformin covers what the supplement aisle's claims actually look like next to thirty years of prescription evidence.

If you are healthy and curious, the cheapest defensible move is an annual HbA1c blood test. Forty dollars cash at Quest. Tells you what the Mass General study just confirmed the CGM cannot tell you anyway: how your body has actually been handling glucose over the past three months. If the number is fine, your pancreas does not need a $99 a month coach. If the number is elevated, that is when a clinician decides whether short-term continuous monitoring would help. Do that. Skip the subscription. For other approaches to metabolic health that have actual outcome data behind them, our explainer on GLP-1 medications walks through what the trials show.

The math is hard to argue with. A Stelo subscription at $99 a month runs $1,188 a year. An A1c test runs forty bucks. The cheaper option is the one that actually predicts diabetes.

---

Frequently asked questions about CGMs for non-diabetics

Are continuous glucose monitors worth it for non-diabetics?

For people with normal or prediabetic blood sugar, the published evidence does not support routine use. The October 2025 Mass General Brigham study of 972 adults found CGM metrics barely tracked HbA1c in the normoglycemic group, with a standardized beta of 0.10. An annual HbA1c blood test costs around $40 cash at Quest. A Stelo subscription costs $1,188 a year and provides data that does not predict diabetes risk in healthy people the way the standard lab test already does.

What did the Mass General Brigham CGM study actually find?

Dr. Jorge Rodriguez and colleagues analyzed 972 adults aged 40 to 85 across three glycemic groups in Diabetes Technology and Therapeutics. In type 2 diabetics, CGM mean glucose tracked HbA1c with a standardized beta of 0.79. In prediabetes, that dropped to 0.22. In people with normal blood sugar, it dropped to 0.10. The team's conclusion was direct: CGM data is not a substitute for HbA1c in non-diabetic adults, and HbA1c remains the test endocrinologists use to predict diabetes.

How accurate are over-the-counter CGMs like Stelo and Lingo?

They are not held to the same accuracy standards as prescription CGMs designed for diabetics. Stelo claims roughly 8.3 percent MARD and Lingo around 9.3 percent, meaning at a real glucose value of 100 mg/dL, readings can drift 8 to 10 mg/dL in either direction. A March 2026 CNN side-by-side test had the two devices reading 3 to 10 mg/dL apart on the same person at the same moment, which is more than enough drift to misinterpret what a meal actually did.

How much does a CGM cost compared to an HbA1c blood test?

Stelo runs $99 a month, or $1,188 a year. Lingo is similar. An annual HbA1c blood test costs roughly forty to seventy-five dollars cash at Quest or Labcorp without a doctor's order in most states. The American Diabetes Association recommends HbA1c every three years for adults over 35, and that single lab test is what physicians actually use to screen for and diagnose diabetes. The cheaper option is the one tied to clinical decisions.

Who should actually use a continuous glucose monitor?

Confirmed prediabetics, people with a strong family history of type 2 diabetes, those with prior gestational diabetes, polycystic ovary syndrome, insulin resistance, or elevated triglycerides have a clinical reason to wear one short term. Two to four weeks of monitoring with a clinician, paired with baseline lab work, can shift habits productively. Healthy non-diabetic adults wearing a CGM as a permanent biofeedback subscription are not the population the published research supports.

Do CGMs improve health outcomes in non-diabetics?

There is no published evidence that they do. Dr. Michael Fang of Johns Hopkins Bloomberg School of Public Health noted in a January 2026 piece that whether the devices improve health outcomes was not part of the FDA's clearance decision. Stelo and Lingo were cleared for over-the-counter sale based on device safety, not on evidence of benefit in healthy users. Harvard Health and endocrinologists quoted by the Mass General Brigham team take the same position: insufficient evidence.