Toxoplasma IgG
An antibody test showing whether a person has been infected with the parasite Toxoplasma gondii, caught mainly from undercooked meat or cat faeces. A positive IgG usually means past exposure and immunity. It matters most in pregnancy and in people with weakened immunity, where infection can cause harm.
What it measures
Toxoplasma gondii is a common parasite people catch from eating undercooked meat, from soil, or from contact with cat faeces. In healthy people, infection usually causes no symptoms or only a mild flu-like illness, after which the parasite lies dormant and the person becomes immune. Toxoplasma IgG is the antibody that reflects this past exposure: once positive, it generally stays positive for life, marking immunity. Depending on the population, a substantial proportion of adults are IgG positive, so the result alone is often unremarkable. Its importance lies in two situations. In pregnancy, a first (primary) toxoplasma infection can pass to the baby and cause harm, so IgG is checked — often with IgM (which suggests a recent infection) and, if needed, an avidity test to date it; a negative IgG means the woman is susceptible and is counselled on food and hygiene precautions. In people with weakened immunity (for example advanced HIV or after transplant), dormant toxoplasma can reactivate and cause serious illness such as brain infection, so IgG status guides prevention. So the test is chiefly a marker of exposure and immune status interpreted according to the setting, rather than a routine test.
What a high value can mean
- Positive toxoplasma IgG — past exposure and, in a healthy person, immunity; a common result.
- Positive IgG with positive IgM — suggests a recent infection; timed with an avidity test where it matters, such as in pregnancy.
- IgG status in immune-weakened patients — guides prevention of reactivation (e.g. brain toxoplasmosis).
What a low value can mean
- Negative toxoplasma IgG — no past exposure; the person is susceptible.
- A negative result in pregnancy — means counselling on food and hygiene precautions, as a first infection then carries risk to the baby.
- A negative status in an immune-weakened person — lower reactivation risk, but new infection still needs avoiding.
When to discuss with a doctor
Toxoplasma IgG is used to establish immune status rather than to diagnose a passing illness. Its key uses are in pregnancy — where a first toxoplasma infection can affect the baby, so IgG, IgM and sometimes an avidity test are interpreted together, and a susceptible (negative) woman is advised on avoiding undercooked meat and cat-litter exposure — and in people with weakened immunity, where a positive IgG flags the risk of the dormant parasite reactivating. In a healthy person outside these settings, a positive IgG simply reflects past exposure and immunity and needs no action. Interpretation depends heavily on the situation. Mediora.AI shows toxoplasma IgG alongside the related markers so the exposure and immune-status pattern is visible; interpretation for pregnancy or reduced immunity belongs with your doctor.