Albumin:Globulin Ratio

A low A:G ratio (relatively less albumin, relatively more globulin) is the more important direction, and it can arise two ways, which is exactly why the ratio is helpful:

• Globulin rising — chronic inflammation, chronic infection, or an antibody-producing process pushing globulins up. In cats especially, a low A:G ratio is one of the supporting findings in certain serious chronic inflammatory diseases.
• Albumin falling — liver disease, protein loss through the gut or kidneys, or inflammation lowering albumin.
• Both at once — inflammation classically does both (albumin down, globulin up), producing a distinctly low ratio.

So a low A:G ratio is a flag to work out which protein is driving it — and that, in turn, points towards the immune system, the liver, the gut or the kidneys.

A high A:G ratio (relatively more albumin, or less globulin) is less common and usually reflects a low globulin — antibody underproduction (an immunodeficiency, important in young animals) or selective globulin loss — or occasionally dehydration concentrating albumin. It, too, is interpreted by asking which protein has changed.

The A:G ratio is at its best as a trend. A slowly falling ratio can be an early, sensitive sign of developing chronic inflammation or an evolving antibody-producing process, sometimes before either protein is dramatically abnormal on its own. Followed over time alongside albumin, globulin and total protein, it helps distinguish a smouldering immune/inflammatory process from a simple protein leak, and tracks whether treatment is bringing the balance back.

The ratio is interpreted the same way in both species, with cats normally running a somewhat lower A:G than dogs. In cats, a low A:G ratio carries particular weight as a supporting finding in certain chronic inflammatory and infectious diseases, and is often one of the numbers that prompts further specific testing. In dogs, a falling ratio similarly flags chronic inflammation, liver disease or protein loss depending on which protein is moving. In both, the ratio directs attention rather than diagnosing on its own.

The A:G ratio is calculated from the measured albumin and the (usually derived) globulin on a routine chemistry panel; it is a ratio and carries no unit. Because it depends on both proteins, it is always read together with them and with total protein. Read the value against your own report's range and, above all, watch its direction over time.

A low A:G ratio is a prompt to identify which protein is responsible — is globulin up (chronic inflammation, infection, an antibody process) or albumin down (liver, gut, kidney, inflammation)? — and to pursue that avenue with your vet, sometimes including serum protein electrophoresis. As a derived pattern, the A:G ratio is followed as a trend rather than treated to a target, and it is one of the more quietly informative numbers on the panel.