The aging biomarkers are alternatives and none of them can act as a strong predictor of frailty during the progression of aging. Several studies reveal the relationship between metabolites and frailty or gut microbiota and frailty. However, the connection between metabolites and gut microbiota in non-robust older adults has not been discussed yet. The study aims to combine the findings of serum metabolites and gut microbiota in non-robust subjects as a possible diagnostic biomarker.