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Category Health & Nutrition

Albumin (g/dL) Range: 0.1 – 7.0 g/dL

Globulin (g/dL) Range: 0.1 – 8.0 g/dL

Total Protein (g/dL) Range: 0.1 – 15.0 g/dL. Must be > Albumin.

A/G Ratio —

Low (<1.1) Normal (1.1–2.5) High (>2.5)

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About

The albumin-to-globulin ratio (A/G) quantifies the balance between the two major serum protein fractions. Albumin, synthesized exclusively by the liver, maintains oncotic pressure and transports hormones, drugs, and fatty acids. Globulins comprise immunoglobulins (IgG, IgA, IgM), complement proteins, and transport proteins like transferrin. A normal A/G ratio falls between 1.1 and 2.5. Deviation signals pathology: values below 1.0 suggest overproduction of globulins (multiple myeloma, autoimmune hepatitis, chronic infection) or underproduction of albumin (cirrhosis, nephrotic syndrome, malnutrition). Values above 2.5 may indicate immunodeficiency or genetic conditions reducing immunoglobulin synthesis.

This calculator accepts direct globulin input or derives it from total protein (TP) minus albumin. Note: results approximate clinical values and do not replace laboratory serum protein electrophoresis. Fasting state, hydration, posture during blood draw, and assay method (bromocresol green vs. bromocresol purple for albumin) introduce variance of ±0.3 g/dL. Always correlate with complete metabolic panel and clinical presentation.

Formulas

The albumin-to-globulin ratio is computed by dividing the serum albumin concentration by the serum globulin concentration. When only total protein is available, globulin is derived first.

A/G Ratio = AlbuminGlobulin

When globulin is not directly reported on the lab panel, derive it from total protein:

Globulin = Total Protein − Albumin

Where Albumin = serum albumin concentration in g/dL, Globulin = serum globulin concentration in g/dL, and Total Protein = sum of all serum proteins in g/dL. The reference interval for a normal ratio is 1.1 to 2.5. Values below 1.0 indicate relative globulin excess or albumin deficit. Values above 2.5 indicate relative globulin deficit.

Reference Data

Condition	Albumin (g/dL)	Globulin (g/dL)	Typical A/G Ratio	Clinical Significance
Healthy Adult	3.5 - 5.5	2.0 - 3.5	1.1 - 2.5	Normal hepatic and immune function
Liver Cirrhosis	1.5 - 3.0	3.0 - 5.0	< 1.0	Reduced albumin synthesis, portal hypertension
Nephrotic Syndrome	1.0 - 2.5	2.5 - 4.0	< 1.0	Urinary albumin loss > 3.5 g/day
Multiple Myeloma	2.5 - 4.0	4.0 - 8.0	< 0.8	Monoclonal immunoglobulin spike on SPEP
Chronic Hepatitis B/C	2.5 - 4.0	3.5 - 5.5	0.6 - 1.0	Polyclonal gamma globulin elevation
Systemic Lupus Erythematosus	2.5 - 3.5	3.5 - 5.0	< 1.0	Autoimmune-driven hypergammaglobulinemia
Malnutrition / Kwashiorkor	1.0 - 2.5	1.5 - 2.5	0.5 - 1.0	Severe protein depletion, peripheral edema
Dehydration	5.0 - 6.5	3.0 - 4.5	1.3 - 2.0	Hemoconcentration falsely elevates both fractions
HIV / AIDS	2.0 - 3.5	4.0 - 6.0	< 0.8	Polyclonal B-cell activation
Pregnancy (3rd Trimester)	2.5 - 3.8	2.5 - 3.5	0.8 - 1.3	Hemodilution lowers albumin concentration
Common Variable Immunodeficiency	3.5 - 5.0	1.0 - 1.8	> 2.5	Deficient immunoglobulin production
X-Linked Agammaglobulinemia	3.5 - 5.0	0.5 - 1.0	> 3.5	Absent B cells, near-zero immunoglobulins
Acute Inflammation	2.5 - 3.5	3.0 - 4.5	0.7 - 1.1	Albumin is negative acute phase reactant
Waldenstrom Macroglobulinemia	2.5 - 4.0	4.0 - 7.0	< 0.7	Monoclonal IgM overproduction
Healthy Neonate	2.5 - 3.4	1.2 - 2.0	1.4 - 2.2	Maternal IgG transferred, own IgM developing

Frequently Asked Questions

A normal albumin level (3.5-5.5 g/dL) can still produce a low A/G ratio if globulin is disproportionately elevated. This occurs in conditions driving immunoglobulin overproduction - chronic infections, autoimmune diseases, or lymphoproliferative disorders. The ratio captures the relative balance, not absolute values. Request serum protein electrophoresis (SPEP) to identify whether the globulin elevation is polyclonal (infection/inflammation) or monoclonal (myeloma, Waldenström).

Bromocresol green (BCG) overestimates albumin by 0.2-0.5 g/dL compared to bromocresol purple (BCP) because BCG binds non-albumin proteins including α₁- and α₂-globulins. This means a BCG-based albumin of 4.0 g/dL might read 3.6 g/dL on BCP, shifting the A/G ratio by approximately 0.1-0.2 units. Always note the assay method printed on your lab report when comparing serial results.

Dehydration concentrates all serum proteins proportionally, so the A/G ratio typically remains stable - both numerator and denominator increase. However, overhydration (IV fluid administration, polydipsia) dilutes both fractions, again preserving the ratio. The ratio shifts meaningfully only when one fraction changes disproportionately. That said, hemoconcentration can push absolute values outside reference ranges, prompting unnecessary workup. A corrected albumin using hematocrit may be warranted.

An elevated A/G ratio above 2.5 most commonly reflects hypogammaglobulinemia - low immunoglobulin levels. Causes include primary immunodeficiencies (common variable immunodeficiency, X-linked agammaglobulinemia), immunosuppressive therapy (corticosteroids, rituximab), or protein-losing conditions that preferentially lose larger globulin molecules. Quantitative immunoglobulin levels (IgG, IgA, IgM) should be ordered to characterize the deficiency.

Yes. Serum protein concentrations fluctuate with posture (standing increases albumin by ~0.3 g/dL vs. supine), diurnal rhythm, recent meals, and exercise. Mixing values from different draws introduces error that can shift the ratio by 0.2-0.4 units. Always use albumin and total protein (or globulin) from the same comprehensive metabolic panel (CMP) or hepatic function panel.

During pregnancy, plasma volume expands by 40-50% by the third trimester, causing hemodilutional hypoalbuminemia (albumin drops to 2.5-3.8 g/dL). Globulin levels remain relatively stable or slightly increase due to immune adaptation. This physiologically lowers the A/G ratio to 0.8-1.3 without implying liver disease. Postpartum values typically normalize within 6-8 weeks. Pregnancy-specific reference ranges should be applied.