Postprandial glucose responses differ greatly between meals, which complicates the identification of individual glucose response traits in free-living conditions. We analysed 50,463 free-living meals from 992 adults without diagnosed diabetes using a multivariate mixed-effects machine-learning framework and evaluated transfer to 4,524 standardized meals excluded from training. This model separated the population-shared from participant-specific patterns across four joint glucose response outcomes. Within-individual variability dominated free-living responses, yet the between-individual variation was concentrated in two dimensions. The dominant axis represented an overall tendency toward larger glucose excursions. The second axis reflected carbohydrate responsiveness with lower late glucose elevations. Dominant-axis scores were reproducible across non-overlapping meal subsets and associated with held-out standardized-meal responses, beyond age, sex, BMI, and glucose mean and variability. Dominant-axis scores estimated from 3 days of monitoring approximated those estimated from 14 days. These findings support short-term monitoring to measure glucose response individuality and identify a candidate coordinate for stratification.