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Blood Test Tracker

Immunoglobulin G (IgG)

The most common antibody in your blood. It shows how much of this main infection-fighting protein your body makes.

AI-verified against cited sources. Awaiting expert reviewAlso called IgGLOINC 2465-3

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What it is

IgG is the most common antibody in your blood. Your immune system makes it after an infection or a vaccine, and it helps your body remember germs it has met. IgG is also the antibody that passes from a pregnant person to the baby. This test measures the total amount of IgG, not how well it works against any one germ.

Why it matters

Total IgG is a simple way to see whether your body makes a typical amount of antibodies. A low level can go with a weaker defense against infection. A high level often reflects long-running inflammation, and sometimes one group of plasma cells making a single antibody (a monoclonal protein), which is why this test is often paired with protein electrophoresis. A result in the usual range doesn't show that your antibodies work well against specific germs.

If it’s low

A low IgG means your blood holds fewer of these antibodies than is usual for your age. Some people are born with a reduced ability to make antibodies, but more often the cause is a medicine, a condition that makes the body lose protein, or a blood condition. Many people with a mildly low level have no symptoms. Many other things can cause this, and your clinician can put it in context.

Common causes

  • Babies, who naturally have low IgG at a few months of age
  • Protein loss through the kidneys (nephrotic syndrome) or the gut (protein-losing enteropathy)
  • Severe burns or malnutrition
  • Blood cancers such as chronic lymphocytic leukemia, multiple myeloma or some lymphomas
  • Medicines, including rituximab, steroids, other immune-suppressing drugs, chemotherapy and some anti-seizure drugs
  • A primary antibody deficiency such as common variable immunodeficiency (uncommon)

What can help

  • Ask whether any of your medicines could be lowering it
  • Ask whether urine protein, kidney tests or gut symptoms need a closer look
  • Ask whether IgA, IgM, IgG subclasses or your response to vaccines would add useful information

If it’s high

A high IgG most often reflects a broad rise from many antibody-making cells, which can happen with long-lasting infections, autoimmune conditions or liver disease. Less often it comes from one clone of plasma cells making a single antibody. Many other things can cause this, and your clinician can put it in context.

Common causes

  • Long-lasting (chronic) infections
  • Autoimmune and connective tissue conditions, such as lupus or rheumatoid arthritis
  • Liver conditions, including hepatitis and cirrhosis
  • Autoimmune liver disease, including autoimmune hepatitis
  • A monoclonal gammopathy, such as MGUS or multiple myeloma (conditions of antibody-making plasma cells)
  • Some lymph node and blood cancers

What can help

  • Ask whether protein electrophoresis would help tell a broad rise from a single-antibody (monoclonal) rise
  • Ask whether your liver tests, inflammation tests or recent infections could explain it

Usual ranges

What labs print as the reference range, by who was tested. Ranges differ a little between labs, so the range on your own report is the one your result is judged against.

The usual range depends on sex and age. Choose women or men to see the one that applies.

Children and teens 12 ranges

See IgG by age and sex, with the U.S. survey numbers where they exist.

What can affect your result

  • Age: IgG is lowest in the first months of life and rises through childhood to adult values by age 18 (Mayo)
  • Sex: Labcorp prints slightly different adult intervals for males and females, while Mayo and ARUP print one interval for all adults
  • Medicines that suppress the immune system, such as rituximab, steroids and chemotherapy
  • Immunoglobulin replacement products (IVIG or SCIG) add donor IgG to the blood, so the result then reflects the infusion as well as your own production
  • Method: nephelometry and turbidimetry assays from different manufacturers are not always comparable
  • Very cloudy (lipemic) samples can't be measured reliably. Mayo rejects grossly lipemic specimens, and ARUP lists grossly hemolyzed and lipemic specimens as unacceptable.
  • Results from different manufacturers' methods may not be comparable, so compare your results using the same lab and method when you can (Mayo).
  • Immunoglobulin infusions (IVIG or SCIG) raise the measured IgG with donor antibody, so tell the person reading your result if you receive them.
  • Medicines that suppress the immune system can lower IgG (Compagno 2014). Tell your clinician about everything you take, and don't stop a medicine without asking.

IgG changes slowly, over weeks to months, because it stays in the blood for a long time.

When to talk to a clinician

Talk with your clinician about a high or low result, especially if you've had repeated or unusually severe infections, or infections that keep coming back despite treatment. Let them know sooner about bone pain, a fracture after a minor injury, numbness or tingling in your hands or feet, or unusual tiredness. An IgG below about 500 mg/dL (5 g/L) is a level researchers use when defining a primary antibody deficiency, so a result that low is worth discussing soon.

Questions you could ask

  • Does my IgG fit with my history of infections?
  • Is my IgG rise broad or from a single antibody, and would protein electrophoresis help?
  • Could a long-lasting infection, a liver condition or an autoimmune condition explain it?
  • Could one of my medicines or another condition be lowering my IgG?
  • Should we check IgA, IgM or my response to vaccines, and recheck this in a few months?

Questions people ask

Why do labs print different IgG ranges?

Labs use different instruments and set their ranges from different groups of healthy people. Adult lower limits run from about 590 to 800 mg/dL and upper limits from about 1,500 to 1,630 mg/dL across Mayo, ARUP, Labcorp and ABIM. Use the range printed on your own report first.

Does a normal total IgG mean my antibodies work well?

Not necessarily. Total IgG tells you how much antibody is present, not how well it protects against specific germs. If immune function is a question, clinicians may also check IgG subclasses and your antibody response to vaccines.

How do I convert g/L to mg/dL?

Multiply g/L by 100. For example, 10 g/L is 1,000 mg/dL. To go the other way, divide mg/dL by 100.

Show the science and sources

Units

  • 1 mg/dL = 1 mg/dL
  • 1 mg/dL = 0.01 g/L
  • 1 mg/dL = 10 mg/L

Open the IgG unit converter

Is a change real?

IgG naturally varies about 2.8% from test to test in the same healthy person. Between two results from the same lab, a change of roughly 9% or more is unlikely to be day-to-day noise or lab variation (95% reference change value). Source: The European Biological Variation Study (EuBIVAS): a summary report.

For clinicians and researchers

IgG makes up roughly 80% of the immunoglobulin in the gamma zone on serum protein electrophoresis (Mayo) and has four subclasses (IgG1 to IgG4). It is measured by nephelometry (Mayo) or immunoturbidimetry (ARUP) against calibrators, and results from different manufacturers may not be comparable. Adult lower limits run from about 590 to 800 mg/dL and upper limits from 1,500 to 1,630 mg/dL across Mayo, ARUP, Labcorp and ABIM. An elevated IgG needs electrophoresis to separate a polyclonal rise from a monoclonal one, and immunofixation to characterize a monoclonal protein; when a monoclonal protein sits on a polyclonal background, serum protein electrophoresis, not quantitative IgG, should be used to follow its size (Mayo). The ESID/PAGID (1999) CVID criteria require IgG below 7–8 g/L (more than 2 SD below the age mean), while Ameratunga et al. (2013) use a 5 g/L threshold in adults, an age over 4 years and exclusion of secondary causes (Ameratunga 2014). Causes of secondary hypogammaglobulinemia include protein loss (nephrotic syndrome, protein-losing enteropathy, burns), CLL, myeloma, non-Hodgkin B-cell lymphoma, Good's syndrome and drugs such as rituximab, belimumab, steroids, azathioprine, tyrosine kinase inhibitors and anticonvulsants (Compagno 2014). Total IgG does not show antibody function. Evaluation of suspected antibody deficiency also uses IgG subclasses and specific antibody responses to protein and polysaccharide vaccines (Yel 2010).

LOINC 2465-3 (primary). Specimen: serum-or-plasma.

Sources

  1. Immunoglobulin G (IgG), Serum (test ID IGG), Mayo Clinic Laboratories
  2. Immunoglobulins (IgA, IgG, IgM), Quantitative (test 0050630), ARUP Laboratories
  3. Pediatric Testing Reference Ranges (includes adult intervals for Labcorp tests 001776, 001784, 001792 and 001834), Labcorp Diagnostics
  4. ABIM Laboratory Test Reference Ranges, January 2026, American Board of Internal Medicine (2026)
  5. Immunoglobulins Blood Test, MedlinePlus (National Library of Medicine) (2025)
  6. Selective IgA Deficiency, Journal of Clinical Immunology (2010)
  7. Comparison of Diagnostic Criteria for Common Variable Immunodeficiency Disorder, Frontiers in Immunology (2014)
  8. Immunoglobulin Replacement Therapy in Secondary Hypogammaglobulinemia, Frontiers in Immunology (2014)
  9. LOINC code lookup (NLM Clinical Tables), National Library of Medicine

AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.

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