Finding the right tests…
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Finding the right tests…
Serology
TYPHOID IGG looks for a longer-lasting antibody against Salmonella Typhi, the bacteria that causes typhoid fever. Unlike IgM, which shows up early and fades, IgG can stay in your blood for more than two years after an infection, so a positive result on its own can't show your doctor if this is a current illness or something you recovered from long ago. In an area where typhoid has circulated for years, this makes a solitary IgG result hard to interpret without other information. Your doctor typically reads it alongside your symptoms, an IgM result, or a blood culture, rather than using it by itself to diagnose an active infection.
Whether IgG antibodies against Salmonella Typhi show up in your blood is what this test reports, as a positive or negative result. Because IgG can remain detectable for more than two years after a typhoid infection, this test on its own can't separate a current illness from one that happened long ago, or in some cases from past vaccination. It's usually ordered together with IgM, or alongside a blood culture and complete blood count, so your doctor has more than one piece of information to work with. A single blood sample is enough, with no special preparation needed.
IgG is the antibody class your immune system keeps making well after an infection has passed, and against Salmonella Typhi it can persist for more than two years. This long persistence is exactly what makes a positive typhoid IgG, tested alone, difficult to interpret in places where typhoid is common — it may reflect an infection from years ago rather than the fever you have today.
When IgG and IgM are checked together, the combination gives more useful timing information than IgG alone: IgM without IgG generally points to an early, current infection, while both being positive together suggests the infection has moved into a middle phase, and IgG alone more often points toward an infection that happened some time ago. Ordering IgG by itself removes some of that context, which is why doctors often prefer it alongside other tests rather than as a stand-alone check.
Because antibody tests for typhoid, including IgG, carry a real risk of false positives and can't clearly separate current from past infection, a blood culture remains the test relied on most to confirm typhoid, even though a result can take several days.
Not necessarily. IgG can stay detectable for more than two years after a typhoid infection, so a positive result on its own doesn't confirm you're currently unwell.
It can persist for more than two years, according to research on typhoid antibody testing, which is why a single IgG result is hard to interpret without other information.
Reading both together gives more timing information — IgM without IgG suggests an early infection, both together suggest a middle phase, and IgG alone more often points toward an older infection.
Some serologic tests for typhoid, including antibody assays, aren't specific enough to reliably tell a past infection apart from vaccination, so tell your doctor about any typhoid vaccination you've had.
This page is general information about the test, not medical advice. Your own report's reference ranges apply — please discuss your results with your doctor.
No. Health guidance advises against relying on antibody tests alone for typhoid because of false positives; a blood culture remains the test used to confirm the diagnosis.
No. No special preparation, including fasting, is needed before this blood draw.
Antibody tests for typhoid, including IgG, carry a real risk of false positives and can't clearly separate a current infection from an old one, so blood culture stays the more trusted confirmatory test.