Albumin/globulin ratio (A/G ratio)

The albumin/globulin ratio (A/G ratio) is calculated from total protein and albumin measurements as albumin divided by (total protein minus albumin), with the globulin fraction encompassing immunoglobulins, complement proteins, acute-phase reactants, and transport proteins. In healthy adults the A/G ratio typically ranges from ~1.1 to 2.5; a lower ratio can result from reduced albumin (malnutrition, liver disease, nephrotic syndrome) or from elevated globulins (chronic inflammation, multiple myeloma, liver cirrhosis, autoimmune conditions), and an inverted ratio (<1.0) warrants investigation. Higher A/G ratio in population studies is associated with better nutritional status and is inversely correlated with systemic inflammation; lower values are independently associated with greater frailty, shorter telomere length, higher all-cause mortality, and accelerated biological aging in several large cohort analyses. As a composite reflecting both hepatic synthetic function and the inflammatory immune response, the A/G ratio can add interpretive context to albumin and globulin assessed in isolation.