Difference Between IgM and IgG Antibodies in Blood Tests

Immunoglobulins are a part of an immune system. There are 5 known types of Immunoglobulins1 – IgG, IgA, IgM, IgD and IgE. But when you’re looking for some pathogen tests, most often you will find two of them – IgM and IgG.


IgG and IgM pathogen tests
The body produces unique antibodies to a a specific infection or parasite which allows to detect whether you were or weren’t exposed to one.

So, what is the difference between IgG and IgM antibodies and what test should we choose then? Or maybe both?

IgM2Produced as a body’s first response to a pathogen approximately one week after the exposure to it. Starts to decline after several weeks after IgG production begins.
IgGStarts to be produced after a few weeks after the exposure to a pathogen. Then during time its levels slowly decrease (can be detected for months or even years later). The body also stores a “blueprint” of all IgG antibodies it has ever made which allows it to rapidly produce them during re-infection.
Does the detection of antibodies shows that the person is still harbouring a pathogen?

No, it doesn’t, it only shows that the person has suffered exposure to it recently or quite in the past.

  1. https://www.ncbi.nlm.nih.gov/books/NBK513460/ ↩︎
  2. https://www.ncbi.nlm.nih.gov/books/NBK555995/ ↩︎


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