A/G Ratio Calculator
Calculate the albumin/globulin ratio from serum albumin and total protein. Includes calculated globulin value, A/G ratio with clinical interpretation, and color-coded flags.
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Disclaimer: For educational purposes only. Not a substitute for clinical judgment.
About This Tool
What Is the Albumin/Globulin Ratio?
The albumin/globulin (A/G) ratio compares the two major protein groups in blood serum. Albumin, produced by the liver, is the most abundant serum protein and is responsible for maintaining oncotic pressure and transporting various substances. Globulins are a heterogeneous group that includes immunoglobulins (antibodies), complement proteins, and transport proteins. The A/G ratio is calculated by dividing albumin by globulin, where globulin is derived from subtracting albumin from total protein.
When Is the A/G Ratio Useful?
The A/G ratio is typically part of a comprehensive metabolic panel (CMP) or hepatic function panel. It serves as a screening tool for conditions that alter serum protein balance:
- Liver disease: The liver produces albumin; cirrhosis and chronic hepatitis reduce albumin synthesis, lowering the A/G ratio.
- Kidney disease: Nephrotic syndrome causes albumin loss in urine, lowering the ratio.
- Immune disorders: Autoimmune diseases and chronic infections elevate immunoglobulins (globulins), lowering the ratio.
- Malignancy: Multiple myeloma and Waldenström's macroglobulinemia produce monoclonal proteins that dramatically increase globulin levels.
- Immunodeficiency: Conditions that reduce immunoglobulin production (e.g., common variable immunodeficiency, certain leukemias) raise the ratio.
Interpreting A/G Ratio Results
A normal A/G ratio is approximately 1.1–2.5, indicating that albumin is the dominant serum protein. Values between 1.0 and 1.1 are borderline. A ratio below 1.0 is clearly abnormal and warrants further investigation with serum protein electrophoresis (SPEP), liver function tests, and renal workup. A ratio above 2.5 may suggest immunoglobulin deficiency.
🔑 Clinical Pearls
- The A/G ratio is a derived value — it is only as accurate as the underlying albumin and total protein measurements. Different assay methods (BCG vs. BCP for albumin) can give different results.
- An abnormal A/G ratio should always be followed up with SPEP to characterize the protein abnormality (polyclonal vs. monoclonal elevation).
- In cirrhosis, both albumin (decreased synthesis) and globulin (increased immunoglobulins from portal hypertension-related endotoxemia) are affected, causing a markedly low A/G ratio.
- Acute-phase reactions (surgery, trauma, infection) transiently lower albumin and raise some globulins — repeat testing after the acute event resolves for accurate interpretation.
Key References
- Burtis CA, Bruns DE. Tietz Fundamentals of Clinical Chemistry and Molecular Diagnostics. 7th ed. Elsevier; 2015. Chapter 18: Amino Acids, Peptides, and Proteins.
- UpToDate. Serum protein electrophoresis and immunofixation electrophoresis. 2024.
- Busher JT. Serum Albumin and Globulin. In: Walker HK, Hall WD, Hurst JW, editors. Clinical Methods. 3rd ed. Butterworths; 1990. Chapter 101.
Formula last verified: February 2026