Limitations of Continuous Glucose Monitors in People Without Diabetes

Continuous glucose monitors (CGMs) are innovative wearable devices designed to track blood sugar levels in real time, primarily aiding individuals managing type 2 diabetes. In 2024, the U.S. Food and Drug Administration approved over-the-counter CGMs for use by both people with and without diabetes. However, there is growing awareness that interpreting CGM data accurately in individuals without diabetes remains challenging.

Recent research conducted by scientists at Mass General Brigham analyzed CGM data from over 970 adults aged 40 and older, including those with diabetes, prediabetes, and normal glycemic levels. The study revealed that while CGM metrics, such as average blood sugar and blood sugar variability, closely correlated with hemoglobin A1c (HbA1c) in people with diabetes—a standard measure of long-term blood sugar control—these relationships weaken considerably in those with prediabetes and are virtually nonexistent in individuals with normal blood sugar levels.

The findings, published in the journal Diabetes Technology and Therapeutics, highlight that CGMs are most beneficial for people with diagnosed diabetes, where they reliably reflect blood sugar control. Conversely, in people without diabetes, the naturally occurring fluctuations in blood sugar caused by meals and activity do not substantially impact HbA1c levels over time. Consequently, CGM data in this group often does not provide meaningful insights into long-term glycemic control.

The study emphasizes that while CGMs can serve as valuable tools for behavioral feedback—helping individuals understand how food and physical activity impact blood sugar—they should not be used as standalone indicators of long-term blood sugar health in those without diabetes. Clinicians and patients should be cautious in interpreting CGM readings outside the diabetic population.

Long-term research is needed to explore whether CGM data could identify at-risk subgroups within the normal HbA1c range who might benefit from early preventive interventions. The researchers also stress the importance of ensuring digital health technologies, including CGMs, are accessible across diverse populations, promoting health equity.

Overall, Dr. Jorge A. Rodriguez from Mass General Brigham notes that for non-diabetic individuals, CGMs are better suited for behavioral insights rather than a substitute for the HbA1c test, which remains the gold standard for evaluating long-term blood sugar control. This distinction is critical as the use of CGMs expands beyond their traditional diabetic population.

Source: https://medicalxpress.com/news/2025-09-people-diabetes-glucose-accurately-blood.html