Continuous glucose monitors without diabetes, what the evidence supports and what it does not

Key takeaways

• Three OTC continuous glucose monitors cleared the FDA in 2024 for adults without diabetes: Stelo (Dexcom, March 2024), Lingo (Abbott, June 2024), and Libre Rio (Abbott, June 2024).
• CGMs measure interstitial glucose, not blood glucose. There is a 5 to 15 minute lag relative to capillary blood glucose, more pronounced during rapid swings.
• Mean absolute relative difference (MARD) for current consumer CGMs is approximately 8 to 10 percent compared with venous reference glucose; this is sufficient for trend tracking but not for diagnostic-grade glucose readings.
• In non-diabetic adults, postprandial glucose excursions to 140 to 180 mg/dL after a typical mixed meal are common and not considered abnormal. The American Diabetes Association does not endorse CGM-derived glycemic-variability targets for non-diabetic adults.
• The published evidence does not support that minimizing every glucose excursion in a non-diabetic adult improves cardiovascular outcomes, weight loss, or longevity.

What a CGM actually measures

A CGM uses a small subcutaneous filament with a glucose-oxidase enzyme that produces hydrogen peroxide proportional to glucose concentration; the reader converts that signal to an interstitial fluid glucose estimate. Interstitial glucose tracks venous and capillary blood glucose with a physiological lag of approximately 5 to 15 minutes. The lag is most consequential during rapid changes (a fast meal-induced spike or a rapid drop during exercise).

Accuracy is reported as mean absolute relative difference (MARD) versus a reference glucose method. Current consumer CGMs (Dexcom G7, FreeStyle Libre 3) report MARDs in the 8 to 10 percent range; the OTC variants share the same underlying sensor platforms with software locked to non-prescription use cases. The FDA's accuracy framework for continuous glucose monitor authorizations is documented in the device-clearance announcement and the published accuracy literature for these sensor platforms .

FDA clearance posture for OTC CGMs

Stelo (Dexcom) was cleared by the FDA on March 5, 2024 as the first OTC continuous glucose monitor in the US, indicated for adults 18 and older not on insulin. Lingo (Abbott) and Libre Rio (Abbott) followed in 2024. None of the three OTC products are intended to make treatment decisions for diabetes; the labeling positions them as wellness devices for adults not requiring insulin therapy .

The FDA News Release announcing Stelo's clearance described the OTC indication as offering glucose-trend information to support lifestyle changes; it did not authorize any specific clinical claim about glycemic-variability targets in non-diabetic adults .

What a non-diabetic glucose curve actually looks like

The Shah et al. 2019 study placed CGMs on 153 non-diabetic adults for 10 days and characterized normal-range glycemic variability. Median 24-hour mean glucose was 98 to 99 mg/dL, with peak postprandial values commonly reaching 140 mg/dL and occasionally up to 180 mg/dL after typical meals. Less than 1 percent of time was spent above 180 mg/dL .

Hall et al. 2018 used CGM in 57 non-diabetic adults to characterize glucose response patterns to standardized meals. Considerable inter-individual variability was observed; the same standardized meal produced different glucose response shapes in different individuals, which is a real phenomenon but does not by itself translate into a clinical recommendation . The Zeevi et al. 2015 trial showed that personalized predictions of post-meal glucose response could be modeled from microbiome and clinical features .

What the evidence supports for non-diabetic CGM use

• Self-experimentation: a CGM is a useful trend-tracking tool for understanding individual postprandial responses to specific meals.
• Behavioral feedback: short-term CGM use has been shown to motivate dietary change in some intervention studies, though long-term outcomes are unclear.
• Detection of dysglycemia: CGM can identify previously unrecognized glucose dysregulation in adults at risk for type 2 diabetes who have not yet been diagnosed.
• Athletic context: some endurance athletes use CGM to manage exercise-induced glucose dynamics; the published evidence supports CGM in elite endurance settings, with mixed results on performance.

What the evidence does not support

• Specific glycemic-variability targets in non-diabetic adults. The American Diabetes Association Standards of Care define time-in-range targets only for adults with diabetes; no equivalent target exists for non-diabetic adults .
• Minimizing every postprandial spike for cardiovascular or metabolic benefit. Postprandial excursions to 140 to 180 mg/dL in a non-diabetic adult are not pathological.
• CGM as a weight-loss tool independent of caloric intake. Trials have not demonstrated CGM-driven weight loss beyond what dietary tracking achieves.
• Use as a diabetes-screening tool in lieu of HbA1c or fasting glucose. CGM accuracy in the prediabetic range is sufficient for trend tracking but not for diagnosis.

Practical framing if you wear one

A non-diabetic CGM trace is a personal physiology log. Trends across days are more informative than any single value. The 5 to 15 minute lag means readings during exercise or post-meal spikes are not directly comparable to a fingerstick. Calibration drift over a wear cycle is normal; the FDA-cleared OTC products use factory calibration with no user-calibration option.

For adults with diagnosed diabetes or impaired fasting glucose, CGM use is a clinical decision and the standards-of-care framework applies. For adults using CGM for self-experimentation, the data are most useful for understanding how specific meals or behaviors affect personal glucose curves, not for benchmarking against a population norm.