[¹⁸F]FDG-PET interpretation relies on comparing an individual’s SUVr against normative data from cognitively normal subjects. However, this comparison is sensitive to technical and biological variability. In this study, we quantified the effects of scanner manufacturer, reference region, age, and sex on regional [¹⁸F]FDG uptake in 449 cognitively unimpaired (CN) adults from ADNI, to derive covariate-adjusted normative values. Scanner manufacturer and age were the dominant sources of variance in brain [¹⁸F]FDG-PET quantification, exceeding sex. Cortical gray matter normalization minimizes confounders, and the AD meta-ROI is highly robust, supporting covariate-adjusted normative data and underscoring the need for harmonization and careful reference-region selection in normative modeling.