Continuous glucose monitors (CGM) are electronic devices that measure the concentration of blood sugar, or blood glucose, and provide the value to its wearer.
Although continuous glucose monitors were initially designed to assist in the clinical management of both insulin-dependent and noninsulin-dependent diabetes, there is now interest in the application of real-time glucose monitoring in the biohacking and athletic communities.
Here marks the first study I’ve read in 2025.
A new paper published in the American Journal of Clinical Nutrition looked at how reliable continuous glucose monitors were in individuals without diabetes.
Briefly, this data was obtained while subjects were admitted to a research facility. All of their meals were prepared for them and while they were instructed to eat as much (or as little) as they wanted, the researchers measured how much food was eaten at each meal.
For this particular study, there were over 1000 direct comparisons in blood sugar measurement after a meal where the Calorie difference and pre-meal blood sugars were very similar.
The variation in blood sugar readings from duplicate meals was about the same as the difference in blood sugar readings between different meals! The authors said of this:
Surprisingly, our study found that the reliability of postprandial CGM responses to many duplicate multicomponent meals was poor and that the within-subject variability to duplicate meals was roughly as large as the variability across different meals.
We talked about this concern in our podcast on continuous blood glucose monitoring. The current crop of monitors are not very reliable for individuals without diabetes, where normal blood sugar changes are smaller than hyperglycemia sometimes seen in individuals with diabetes.
Reliability issues aside, there’s little evidence suggesting that health improves when people make lifestyle changes based on continuous glucose monitoring data. For now, I don’t think there is a legitimate use case for CGM in individuals without diabetes or metabolic syndrome.