Autoimmune Panel

Immunoglobulin G (IgG)

One IgG number, two very different stories: a broad immune response, or a single cell multiplying on its own.

Part of the Autoimmune Panel — see all 16 values together, including Anti-Centromere Antibodies, Anti-Cyclic Citrullinated Peptide, Anti-Double Stranded DNA.

The same IgG total can mean a busy, varied immune system or one cell copying itself, and the number printed on the report looks identical either way. Immunoglobulin G is the long-term, specialized antibody the body keeps after it has cleared an infection, while IgM is the class made first for short-term protection and IgA guards the lining of the airways and gut. A quantitative IgG test does not catalogue which infections you have met. It weighs all of that antibody at once and reports a single bulk figure.

Think of that figure as one bank balance. A healthy-looking balance tells you how much sits in the account, but it says nothing about how the money arrived. The same total could be a thousand small deposits, a little from many different account-holders, or one large and suspicious wire transfer from a single source. IgG behaves the same way. The number can climb because dozens of distinct immune cells are all producing antibody together, or because one cell line has started multiplying and is flooding the account on its own.

The bare total cannot tell those two stories apart. The broad version, called polyclonal, is the reactive pattern of infection, autoimmune disease, and liver trouble, and it is usually benign. The single-source version, called monoclonal, comes from one clone and can be benign or the early edge of something that needs watching. Separating them takes a different test, serum protein electrophoresis, which is built to show the shape behind the number.

What the number can and can't tell you

mg/dL
Below the usual range < 700

Low total IgG can show up in people who keep getting sick with the same respiratory or sinus infections. One IgG subclass can also run low while the total still reads normal, so a doctor may look deeper than the single figure.

Within the usual range 700–1600

Where most adults land. A normal total does not completely rule out a small monoclonal band hiding inside the range, which is why electrophoresis is sometimes run even when the total looks fine.

Above the range, shape unknown > 1600

The figure that brings people here. A total of 1650 sits just over the line; 1700, 1800, or 2000 mg/dL push further above it. A slightly elevated result and a steep one raise the same question, because none of these numbers, on their own, say whether the rise is polyclonal or monoclonal.

What does a high IgG mean?

A raised total IgG has a short list of usual explanations. MedlinePlus names chronic or repeated infection, hepatitis and cirrhosis, autoimmune disease, and cancers including multiple myeloma and lymphoma. That list mixes the reassuring with the serious, which is exactly the problem the number creates: it points at all of them at once and commits to none.

The honest read is that most high totals are polyclonal. AFP describes this reactive pattern, driven by infection, connective tissue disease such as lupus or rheumatoid arthritis, and liver disease, as the broad and usually nonmalignant kind. Feeling run-down or tired with a high IgG more often reflects the underlying infection or autoimmune flare than the antibody itself.

What can push IgG high

  • Chronic or repeated infection

    A long-running immune response keeps many clones producing antibody.

  • Autoimmune disease

    Lupus and rheumatoid arthritis are classic polyclonal drivers in this Autoimmune category.

  • Liver disease

    Hepatitis and cirrhosis both raise the gamma fraction, per MedlinePlus.

  • A single clone

    MGUS, multiple myeloma, or Waldenstrom macroglobulinemia, where one cell line dominates.

The two shapes deserve a closer look, because the whole reason this page exists is that the total alone hides them. Serum protein electrophoresis spreads serum proteins across a gel and lets the lab see the gamma region directly.

The two shapes behind the same number

Polyclonal: the broad rise

SPEP gamma band · broad and diffuse Light chains · both kappa and lambda Total IgG

Many clones answering at once. AFP describes this band as multiple heavy chains with both kappa and lambda light chains, reflecting a reactive process in infection, lupus, rheumatoid arthritis, or liver disease, and it is usually nonmalignant.

Monoclonal: the single spike

SPEP gamma band · sharp and narrow Light chains · one kappa or lambda Total IgG

One clone copying itself, seen as a sharp, well-defined band with a single heavy chain and a single light chain. AFP calls this clonal and potentially significant, as in multiple myeloma or Waldenstrom macroglobulinemia. A narrow distinct spike is followed by immunofixation, a more sensitive test that names the exact heavy and light chain and confirms the clone.

A monoclonal spike is not automatically cancer. The most common finding is MGUS, monoclonal gammopathy of undetermined significance, which the NEJM defines as a monoclonal protein of 3.0 g/dL or less in someone without symptoms and is usually discovered by accident during testing for something else. It is common and grows more so with age: NEJM's Olmsted County data found it in 3.2% of people 50 or older, 5.3% of those 70 or older, and 7.5% of those 85 or older. On average, MGUS progresses to myeloma or a related condition at a rate of about 1% per year, which is why it is monitored rather than ignored.

The mismatch pattern is worth knowing too. MedlinePlus notes that some cancers show very high levels of one immunoglobulin type alongside low levels of the others, so a doctor reads IgG next to IgM and the IgA reference of 40 to 220 mg/dL rather than in isolation.

What does a low IgG mean?

A low total points the other direction. When IgG runs short, the body has fewer long-term antibodies on hand, and the practical sign is often someone who keeps getting sick with the same kinds of infection. A single IgG subclass can also be deficient while the overall total looks unremarkable, so persistent infections with a normal-seeming number are still worth raising with a doctor.

After an unexpectedly high IgG

  1. 1

    Start with your doctor

    Bring your symptoms, recent infections, and any prior results. The figure means little without that context, and a one-off high reading is often repeated before anything else happens.

  2. 2

    Serum protein electrophoresis

    This is the test that resolves the shape. AFP describes it as separating a broad polyclonal band from a sharp monoclonal spike, which the total can never do on its own.

  3. 3

    Immunofixation if a spike appears

    When electrophoresis shows a narrow distinct spike, AFP describes immunofixation as the confirmatory step that identifies the specific heavy and light chain and proves the rise is clonal.

  4. 4

    Watch the trend over time

    If the answer is MGUS, doctors monitor it on a schedule because of that roughly 1% yearly progression NEJM describes. A direction across several draws tells more than any single value.

IgG in context

IgG is the largest slice of the globulin fraction, and it is part of what a total protein measurement sums up, so an unexplained shift in those broader numbers often traces back to it. It also sits alongside the other antibody classes, including IgE, which a doctor may measure together when the picture is unclear. If you are trying to make sense of where this fits among the rest of your results, the guide to blood test results lays out how the immunoglobulins relate to one another. The one habit worth keeping is to treat IgG as a number with a shape: the figure starts the conversation, and electrophoresis finishes it.

Sources

Written and reviewed by BloodSight Editorial Team · Last updated

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Normal ranges

Group Range Unit
Adult Male 700–1600 mg/dL
Adult Female 700–1600 mg/dL

Reference ranges may vary by laboratory and individual factors.

Immunoglobulin G — Common Questions

If my total IgG is high, does that mean I have cancer?
Usually not. MedlinePlus lists chronic infection, liver disease, and autoimmune conditions among the common reasons IgG climbs, and most of those are polyclonal rises that AFP describes as reactive and nonmalignant. A small share of high totals come from a single clone, which is why a doctor orders electrophoresis rather than guessing from the number.
Why does my doctor want serum protein electrophoresis after a high IgG?
The total IgG figure measures how much antibody is present, not what shape produced it. Serum protein electrophoresis spreads the proteins out so the lab can see whether the gamma region is a broad, diffuse band (many clones) or a sharp, narrow spike (one clone). AFP describes that band shape as the thing that separates a reactive rise from a clonal one.
What is the difference between polyclonal and monoclonal IgG?
Polyclonal means many different immune cells are each making antibody at once, so the rise contains multiple heavy chains and both kappa and lambda light chains. Monoclonal means one cell line is copying itself, producing a single heavy chain and a single light chain. AFP notes the first pattern is typically reactive and the second is clonal.
Can a high IgG just be from an infection or autoimmune disease and be harmless?
Yes. AFP describes the polyclonal pattern, common in infection, lupus, rheumatoid arthritis, and liver disease, as a reactive process that is usually nonmalignant. The level alone does not decide this, so the band shape on electrophoresis is what tells a doctor whether the rise is the reassuring kind.
What does it mean if one immunoglobulin is very high and the others are low?
MedlinePlus notes that some cancers show very high levels of one immunoglobulin type and low levels of the others. That mismatch is one of the patterns that prompts a doctor to order serum protein electrophoresis and, if a spike appears, immunofixation to identify the clone.
Is a mildly elevated IgG something to worry about?
A modestly high total is often a reactive polyclonal rise tied to a recent or ongoing infection or an autoimmune condition. Whether it needs further work depends on your symptoms, the rest of the panel, and the trend over time, which is a conversation for your doctor rather than a single reading.

Disclaimer

This content is for informational and educational purposes only. It is not intended as medical advice, diagnosis, or treatment recommendation. Reference ranges may vary by laboratory. Always discuss your results with a qualified healthcare professional.

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