Continuous Glucose Monitors Overestimate Glycemic Responses
By Elana Gotkine HealthDay Reporter
THURSDAY, March 6, 2025 -- Continuous glucose monitoring (CGM) can overestimate glycemic responses, according to a study published online Feb. 26 in The American Journal of Clinical Nutrition.
Katie M. Hutchins, from the University of Bath in the United Kingdom, and colleagues examined glycemic responses to different test foods/beverages using CGM versus capillary sampling among 15 healthy female and male participants (nine and six, respectively). Participants completed seven laboratory visits in a randomized crossover design with washout of ≥48 hours between visits. At each visit, participants consumed an oral carbohydrate challenge composed of either 50 g glucose or equivalent carbohydrate as a whole-fruit, blended-fruit, or commercial fruit smoothie.
The researchers found that compared with capillary estimates, CGM-estimated fasting and postprandial glucose concentrations were 0.9±0.6 and 0.9±0.5 mmol/L higher, respectively. There was variation in CGM bias by postprandial test, with the glycemic index for commercial fruit smoothie higher with CGM than capillary (69 versus 53). There was variation by participant in the differences in CGM versus capillary fasting glucose concentrations. Time >7.8 mmol/L was overestimated by about fourfold with CGM in unadjusted analyses; this overestimate was reduced to about twofold after adjustment for baseline differences.
"These data demonstrate that a CGM can overestimate postprandial glycemia, and to differing degrees across foods/beverages," the authors write. "Therefore, if accurate quantification of postprandial glycemia is the primary aim, then capillary blood should be the preferred method and CGM may not be suitable, at least with respect to the CGM device tested in the present study."
Several authors disclosed ties to the pharmaceutical, nutrition, and other industries; the data were supported by an unrestricted grant from Innocent Drinks.
Disclaimer: Statistical data in medical articles provide general trends and do not pertain to individuals. Individual factors can vary greatly. Always seek personalized medical advice for individual healthcare decisions.

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Posted March 2025
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