IgG

Most UK laboratories print 6.0 to 16.0 g/L for adults; ranges are lower in children and differ slightly between methods.

IgG is the most plentiful antibody in the blood, the type the immune system makes in the weeks after meeting an infection or vaccine and keeps for years afterwards. The test measures the total amount of IgG, of all specificities put together, not antibody to any one germ. It is usually reported together with IgA and IgM.

Doctors request the three main immunoglobulins together when looking at recurrent infections, at unexplained high blood protein or a high ESR or plasma viscosity, and as part of the tests for myeloma and related conditions.

• Long-term infections and inflammatory conditions
• Liver disease, particularly autoimmune and alcohol-related
• Myeloma and related conditions, where one clone of cells makes a single type of antibody
• Some autoimmune conditions
• HIV infection, in the general population

• Immune-suppressing medicines, including steroids, rituximab and chemotherapy
• Protein loss through the kidneys or the gut
• Inherited and acquired immune deficiencies
• Some blood cancers
• Poor nutrition and severe burns

• It is lower in the first months of life and slightly lower in old age
• Methods differ between laboratories
• A recent infection or vaccination raises it modestly for some weeks

No fasting needed. Read alongside IgA, IgM and serum protein electrophoresis from the same sample; a single value is usually enough unless following a known condition.

Written by a UK consultant physician. Typical UK adult reference ranges; your laboratory's own printed range takes precedence.