The albumin/globulin (A/G) ratio compares the two main categories of blood protein — albumin and globulin — to help screen for liver disease, kidney disease, and conditions that raise antibody or other globulin levels. This calculator derives globulin from total protein and albumin, then computes the A/G ratio and classifies it against the standard reference range.

How the A/G ratio is calculated

A routine metabolic panel reports total protein and albumin directly, but globulin is not measured on its own — it is calculated as Globulin = Total Protein - Albumin. The A/G ratio is then Albumin / Globulin. Both total protein and albumin are entered in g/dL; the resulting ratio is unitless.

A normal A/G ratio is roughly 1.1 to 2.5:1, meaning albumin normally outweighs globulin by a modest margin. This reference range reflects standard clinical chemistry practice (Mayo Clinic Laboratories; MedlinePlus Medical Encyclopedia).

What drives a low A/G ratio

A low A/G ratio can come from either side of the equation: reduced albumin, elevated globulin, or both. Reduced albumin production is common in chronic liver disease, since the liver is the sole site of albumin synthesis. Albumin can also be lost directly through the kidneys in nephrotic syndrome or through the gut in protein-losing enteropathy.

On the globulin side, chronic inflammation and autoimmune disease raise immunoglobulin levels, and a paraproteinemia — most notably multiple myeloma — can sharply raise a single monoclonal globulin. A low A/G ratio, particularly with a high total protein and a normal albumin, is a classic pattern that prompts a serum protein electrophoresis (SPEP) to look for a monoclonal spike.

What drives a high A/G ratio and limitations

A high A/G ratio is less common and less specific than a low one. It is most often seen with dehydration, which concentrates albumin and total protein proportionally without necessarily changing the underlying protein composition, or with conditions that reduce globulin (antibody) production.

The A/G ratio is a screening calculation, not a diagnosis. It does not identify which specific protein is abnormal or why — an abnormal result should be interpreted alongside the total protein and albumin values individually, the rest of the clinical picture, and follow-up testing such as SPEP when a paraproteinemia is suspected.