Immunoglobulin G (IgG)
Also called: IgG, Immunoglobulin G, Total IgG
The most abundant antibody in the blood and the mainstay of long-term immunity — it carries the 'memory' of past infections and vaccinations. A low total IgG can signal an immune deficiency, while a high level often reflects chronic infection or inflammation.
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What does Immunoglobulin G (IgG) measure?
Immunoglobulin G is the most common antibody class and the backbone of lasting, specific immunity. It is produced after the initial response to an infection or vaccine and provides durable protection, which is why IgG antibodies are what tests look for to show past infection or immunity. Total IgG measures the overall amount. It is checked mainly in two situations: to investigate recurrent or unusual infections, where a low IgG can indicate an antibody (immune) deficiency that may benefit from treatment; and to investigate a raised total protein or suspected blood condition, where a markedly high, single-type (monoclonal) IgG can point to a plasma-cell disorder such as myeloma, while a broadly raised (polyclonal) IgG reflects chronic infection, inflammation or liver disease. IgG is usually measured alongside IgA and IgM to see the whole antibody picture.
What does a high Immunoglobulin G (IgG) level mean?
- Chronic infection or inflammation — a broad (polyclonal) rise; also autoimmune and liver disease.
- Monoclonal rise (a single IgG type) — can indicate a plasma-cell disorder such as myeloma or MGUS; investigated with protein electrophoresis.
- Some chronic liver conditions (e.g. autoimmune hepatitis).
What does a low Immunoglobulin G (IgG) level mean?
- Antibody (immune) deficiency — inherited (common variable immunodeficiency) or acquired; important because it can cause recurrent infections and may be treatable with immunoglobulin replacement.
- Protein loss — from the kidneys (nephrotic syndrome) or gut.
- Some medications and blood conditions.
When to discuss with a doctor
Total IgG is worth checking in someone with recurrent, severe or unusual infections, where a low level can reveal a treatable antibody deficiency and prompt referral to immunology. It is also part of the work-up for a raised total protein or suspected myeloma, where a monoclonal IgG on protein electrophoresis needs specialist assessment. A broadly raised IgG usually reflects chronic infection, inflammation or liver disease and is interpreted in that context. IgG is read together with IgA and IgM. Mediora.AI shows IgG alongside the other immunoglobulins so the antibody pattern is visible; the interpretation belongs with your doctor.
Related markers
Commonly confused with
- Immunoglobulin A (IgA) Both are immunoglobulins, but they work in different places. IgA guards the surfaces - gut, airways, saliva. IgG circulates in the blood and carries long-term memory of past infections and vaccinations.