High IgG Blood Test: What Does a Raised IgG Level Mean?

A high IgG blood test means your blood contains more immunoglobulin G, the most common type of antibody, than the laboratory's reference range. It often reflects an immune system that is working hard, for example because of a chronic infection, an autoimmune condition or liver disease. MedlinePlus notes that a high level does not always mean a condition that needs treatment.

This guide is for adults reviewing a raised IgG result. It explains the main patterns and the usual next tests. It cannot tell you the cause of your result; that depends on your symptoms, examination and other tests.

Most people with a raised IgG feel well, and the result is often found on a routine test. Some symptoms need prompt attention, whatever the IgG result shows.

Cleveland Clinic advises seeking care promptly for headaches or vision changes, which can occur if very high antibody levels make the blood thicker. The NHS advises an urgent appointment for new or worsening shortness of breath. It advises calling emergency services for any of the following. Outside the UK, use your local emergency number.

• Sudden loss of feeling in the arms or legs, or suddenly being unable to walk or stand.
• Sudden confusion.
• Suddenly being unable to control the bladder or bowels.

Immunoglobulins are antibodies made by plasma cells, a type of white blood cell. MedlinePlus describes IgG as the most common antibody. The body makes IgG in response to a specific germ. It then keeps a memory of it, so the immune system can respond faster next time.

IgG is one part of the globulin fraction in the blood. If your report showed a high total globulin or a low albumin-to-globulin ratio, our guide on high globulin explains those results. This guide focuses on IgG itself.

Cleveland Clinic explains that the difference is the number of cell types making too many antibodies. In a polyclonal rise, many different groups of B cells and plasma cells produce extra antibodies. This is a broad immune response. It is not usually serious in itself, but it can point to infection, inflammation or another condition.

In a monoclonal rise, a single group of plasma cells makes large amounts of one identical antibody, called an M protein or paraprotein. MedlinePlus notes that blood cancers such as multiple myeloma often cause one antibody type to be very high while others are low.

A monoclonal protein found without signs of cancer is often MGUS (monoclonal gammopathy of undetermined significance). Our MGUS guide explains what it means and how it is monitored.

Cleveland Clinic notes that polyclonal gammopathy itself does not cause symptoms and has no specific treatment. Clinicians look for and treat the underlying condition, and may monitor immunoglobulin levels over time. Any symptoms you have, such as fatigue, fever, stiff joints or swollen lymph nodes, may come from that underlying condition, so mention them even if they seem unrelated.

MedlinePlus and Cleveland Clinic list several groups of conditions linked with raised immunoglobulins:

• Chronic infection: Cleveland Clinic gives examples including HIV, tuberculosis and malaria.
• Autoimmune conditions: such as lupus, rheumatoid arthritis and Sjögren's syndrome.
• Liver disease: including viral hepatitis, autoimmune hepatitis and cirrhosis.
• Some blood disorders and other cancers, which Cleveland Clinic also lists as associated conditions.

Cleveland Clinic describes IgG4 as one of four subtypes of IgG. Some people have IgG4 measured separately when a clinician is considering IgG4-related disease. Cleveland Clinic describes this as a rare, long-term inflammatory condition that can cause swollen organs or tumour-like masses that are not cancer. It can affect organs such as the pancreas, bile ducts, salivary and tear glands, kidneys and lungs.

Cleveland Clinic notes that IgG4-related disease can be tricky to diagnose and that a large part of the process is ruling out other conditions. Diagnosis usually draws on blood tests, imaging and sometimes a biopsy, rather than one blood value. If IgG4 was raised, ask why it was measured and what else is being checked.

The next step depends on the size of the rise, your symptoms and your other results. MedlinePlus lists protein electrophoresis as a test used to check for and monitor conditions linked to abnormal antibody production. Serum protein electrophoresis separates blood proteins into groups, including a gamma globulin fraction. The pattern helps a clinician judge whether the rise looks polyclonal or monoclonal.

A related test, immunofixation, measures the number and type of proteins in the blood and may be arranged when other results are abnormal. A clinician may also arrange tests for the likely underlying cause, such as liver tests, infection screening or autoimmune antibody tests.

Reference ranges vary between laboratories. As an example, MedlinePlus gives a gamma globulin range of 0.8 to 1.8 g/dL (8 to 18 g/L) on electrophoresis. Use the range printed on your own report.

Bring the full report, with units, reference ranges and any earlier immunoglobulin results.

• Is my IgG rise polyclonal or monoclonal, and how was that decided?
• Were IgA and IgM also measured, and were they high, normal or low?
• Which cause do you think is most likely: infection, autoimmune disease, liver disease or something else?
• Do I need protein electrophoresis, immunofixation or other tests?
• If IgG4 was measured, why, and what else will be checked?
• When will the test be repeated, and which new symptoms should make me seek help sooner?

On SameCase, patients and verified doctors share de-identified cases. Reading cases with a similar result, such as a raised IgG with normal electrophoresis, can show which questions others asked. It can also show which other results formed part of their discussion.

Another person's case cannot explain your own result or predict what will happen. We suggest using similar cases only to prepare questions for the clinician who knows your history and can examine you.