SARS-CoV-2 Immunoglobulin M (IgM) Antibody Test by Titration (Serum/Plasma)

What Does This Test Measure?

IgM antibodies are part of your immune system’s immediate response to infection. When your body detects SARS-CoV-2, it produces IgM antibodies within days to weeks. This test quantifies these antibodies to determine if you’ve recently been infected. Unlike IgG antibodies, which can linger longer, IgM levels usually peak early and drop as your body transitions to producing other protective antibodies.

Why Might You Need This Test?

Doctors may order this test if you’ve recently tested positive for COVID-19 symptoms, have been exposed to someone with COVID-19, or if you’re recovering from an infection. It can also help monitor immune response in certain clinical settings. However, IgM alone is not definitive for diagnosing COVID-19, as it may not be present in all infected individuals or may fade quickly.

When Are IgM Antibodies Most Reliable?

IgM antibodies are most likely to be detected about 1–2 weeks after initial infection, but their presence doesn’t always mean you’re actively contagious. They can also be influenced by prior vaccination or exposure, so results should be interpreted alongside clinical symptoms and other tests.

What Does a Positive Result Mean?

A positive IgM result suggests you may have had an active SARS-CoV-2 infection at some point, but it doesn’t confirm current infection. IgM levels can vary widely and may not be stable over time. Always discuss your results with your healthcare provider for guidance.