Cytomegalovirus (CMV) Antibody (IgG and IgM)
This blood test looks for two types of antibodies against cytomegalovirus (CMV), a common virus in the herpesvirus family: IgM, which tends to reflect a recent or current infection, and IgG, which reflects past exposure and lasting immunity.
CMV is very common and usually causes no symptoms in healthy people, but it matters in certain situations, such as during pregnancy or for people with weakened immune systems, where infection can be more serious. Measuring IgM and IgG helps show whether an infection is recent or from the past, and whether you have been exposed before.
A positive result means CMV antibodies were detected. A positive IgM often suggests a recent or current infection, while a positive IgG indicates past exposure and generally lasting immunity. IgM results can sometimes be positive for other reasons, so a single positive result may need additional testing (such as IgG avidity or repeat testing) to confirm the timing of infection. Your clinician interprets the pattern in context.
A negative result for both antibodies generally means you have not been infected with CMV and do not have immunity to it, which means a first-time infection remains possible. Because antibodies take time to appear after exposure, a very recent infection could occasionally be missed and may warrant repeat testing.
There is no single target value; results are interpreted as a pattern. Many healthy adults have a positive IgG and negative IgM, consistent with a past infection and immunity. Your clinician will interpret the IgM and IgG results together, taking into account your health, symptoms, and situations such as pregnancy.
Sources
Educational context only, not medical advice or a diagnosis. Reference ranges vary by lab, age and sex; always discuss your results with a clinician.