Meaning of the Albumin/Globulin (A/G) Ratio

Liver HealthQ&AMeongsiljang Veterinary Advisory Board

The A/G ratio is a key indicator that reflects the balance of proteins in the blood. It is used in diagnosing liver disease, chronic inflammation, and dehydration, and understanding how to interpret it makes it easier to comprehend test results.

What is the A/G Ratio and Why is it Important?

A blood test report showing albumin and globulin levels.

The albumin-to-globulin ratio (A/G ratio) is calculated by dividing the albumin level by the globulin level in the blood, serving as a key indicator that provides a clear snapshot of liver function, immune status, and protein metabolic balance. What truly matters is not the individual values, but rather the balance between them. Even if total protein levels are within the normal range, an abnormal A/G ratio may indicate underlying liver disease, chronic inflammation, or infection. Therefore, it is essential to evaluate this ratio alongside other markers during routine health screenings.

What Roles Do Albumin and Globulin Play?

Albumin is the most abundant serum protein, produced exclusively by the liver. It helps retain fluid within blood vessels (maintaining osmotic pressure) and acts as a carrier for drugs, hormones, and fatty acids. Globulins are divided into three types: alpha, beta, and gamma. Gamma globulins, in particular, serve as antibodies (immunoglobulins) and play a key role in defending against infections. An imbalance in the ratio between albumin and globulin may indicate abnormalities in liver production or immune/inflammatory responses.

General Reference Ranges for Dog and Cat A/G Ratios

Item	Dog	Cat
Total protein (TP)	5.5–7.5 g/dL	6.0–8.0 g/dL
Albumin (ALB)	2.5–4.0 g/dL	2.5–3.9 g/dL
Globulin (GLOB)	2.0–3.7 g/dL	2.5–5.1 g/dL
A/G ratio (reference)	About 0.6–1.1	About 0.4–0.9

Reference ranges differ by laboratory, so always interpret based on the reference range printed on the test report.

What Does a Low A/G Ratio Mean?

A low albumin-to-globulin (A/G) ratio means that albumin has decreased, globulin has increased, or both. Rarely, even if globulin also decreases, the ratio can drop if albumin decreases more significantly. Veterinary textbooks refer to this pattern as "dysproteinemia" and use it as the first fork in the road when investigating the cause. - Decreased albumin: Liver dysfunction, protein-losing enteropathy (PLE), proteinuria/glomerular disease, malnutrition - Increased globulin: Acute or chronic infections, immune-mediated diseases, and other inflammatory stimuli - Changes in both: Chronic liver disease, systemic inflammation In particular, a low A/G ratio in cats is a finding commonly expected in feline infectious peritonitis (FIP). However, it is not specific to FIP alone, so differential diagnosis requires considering symptoms alongside other test results.

A veterinarian examining a puppy's abdomen

When Additional Testing is Essential

If the A/G ratio remains persistently low and is accompanied by symptoms such as decreased appetite, ascites, jaundice, and weight loss, further diagnostic testing is necessary rather than simply monitoring the condition. Tests such as abdominal ultrasound, detailed liver function tests (bile acids and ammonia), urine protein-to-creatinine ratio (UPC), and serum protein electrophoresis (SPE) can help identify the underlying cause. Conversely, an elevated A/G ratio may suggest hemoconcentration due to dehydration (resulting in hyperalbuminemia) or conditions characterized by reduced globulin levels, such as congenital or acquired hypoglobulinemia.

When the A/G Ratio is High — Unexpected Signals

An elevated A/G ratio is uncommon, but it’s a sign that shouldn’t be overlooked. The main causes can be summarized as follows: - Dehydration (hemoconcentration): When dehydration occurs, the blood becomes more concentrated, leading to an overall increase in serum protein levels, including albumin. This rise in albumin due to hemoconcentration (hyperalbuminemia) is one of the factors that can cause an increased A/G ratio. - Decreased globulin (in young animals): In puppies and kittens, globulin and total protein levels are typically lower than adult reference ranges until about 8 weeks of age, after which they gradually increase with growth. - Hypoglobulinemia: If there is reduced production of immunoglobulins or increased loss of globulins through the intestines, kidneys, or other organs, globulin levels may drop relative to albumin, potentially raising the A/G ratio. It’s important not to diagnose based on a single value alone. The results should always be interpreted alongside clinical symptoms and other blood test values.

Key Points to Check When Reviewing Test Results

Here are the key points to keep in mind when reviewing your pet’s test results: - Total Protein (TP): First, check whether the value is within the normal range or if it has increased or decreased. - Albumin (ALB): Compare the individual value against the reference range. - Globulin (GLOB): Calculated as TP minus ALB; an increase may indicate inflammation or infection. - A/G Ratio: The direction of change (↑/↓) compared to previous tests is what matters most. - Recheck Recommended: Trends observed over 2–3 weeks are more accurate than a single reading. Rather than worrying about one number, the key is to look at the big picture together with your veterinarian.

Daily Care and Related Content

The A/G ratio is closely tied to liver, kidney, and immune health, so daily care plays a major role in keeping it stable. The basics are maintaining a healthy weight and muscle mass, and getting regular check-ups to catch chronic enteritis or proteinuria before they cause protein loss. If your liver enzymes are also elevated, check out our article Causes and Management of Elevated Liver Enzymes in Dogs for more details. If proteinuria is present, you’ll need to focus on kidney care as well.

Reviewed by a veterinarian

Dr. Tony — Punnawat Phongkittirak

Veterinarian

A veterinarian who majored in veterinary medicine at Khon Kaen University, Thailand, and completed the IVSA program at North Carolina State University in the United States. Drawing on clinical experience at animal hospitals, he works in the pet healthcare field and is dedicated to building a digital care environment that connects pet parents with veterinarians.

Frequently Asked Questions

The A/G ratio is slightly low, but there are no symptoms. Does this require immediate treatment?

If there are no symptoms and other values are normal, it's common to recheck in 2–4 weeks to monitor the trend. However, if weight loss or decreased appetite is present, I recommend immediate detailed testing.

Do pet food or treats affect the A/G ratio?

Prolonged adherence to an extremely low-protein diet or chronic malnutrition can lower albumin levels and reduce the ratio. However, in pets that eat a standard commercial diet well, diet alone is unlikely to cause significant changes.

Can dehydration alone change the A/G ratio?

Yes. Dehydration can cause the blood to become more concentrated, leading to an overall increase in serum protein levels, including albumin. This dehydration-induced rise in albumin (hyperalbuminemia) is one of the factors that can elevate the A/G ratio. If dehydration is suspected, we recommend retesting after proper hydration.

Do dogs and cats have different normal ranges?

Yes, reference ranges vary by species, so the same numerical value can be interpreted differently. Therefore, results for dogs and cats should be evaluated against their respective species-specific reference ranges, and you must always interpret the results using the species-specific reference range printed on the test report. Additionally, keep in mind that in puppies and kittens around eight weeks of age, globulin and total protein levels may be lower than the adult reference ranges.

When is serum protein electrophoresis (SPE) performed?

When the A/G ratio is significantly low and globulin levels are markedly elevated, this test is recommended to identify which protein fraction has changed. Veterinary clinical pathology textbooks also introduce serum protein electrophoresis (SPE) as a key tool for additional differential diagnosis, often used in conjunction with immunoelectrophoresis or immunoglobulin measurements.

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References

[1] Stockham SL, Scott MA. Fundamentals of Veterinary Clinical Pathology, 3rd Edition. Wiley-Blackwell, 2013. Chapter: Proteins

[2] Thrall MA et al. Veterinary Hematology and Clinical Chemistry, 2nd Edition. Wiley-Blackwell, 2012.

[3] Ettinger SJ, Feldman EC. Textbook of Veterinary Internal Medicine, 8th Edition. Elsevier, 2017.