Immunity and viral serology . Patient guide
Rubella immunity (Rubella IgG) Blood Test
Also known as: Rubella antibody test, German measles immunity
What is Rubella IgG
Rubella IgG measures the protective antibody response to the rubella virus, usually from MMR vaccination. It is most commonly requested when planning a pregnancy, because rubella infection in the first 16 weeks of pregnancy can cause congenital rubella syndrome with serious effects on the developing baby.
This biomarker entry is being clinically reviewed by our team. The factual content draws on UK guidance (NICE, NHS, Royal Colleges and the relevant speciality society where cited).
Reference range
Reported in IU/mL. Final reports always carry the issuing laboratory's range, which is what your clinician will interpret against.
| Group | Range | Note |
|---|---|---|
| Non-immune (negative or equivocal) | less than 10 IU/mL | MMR vaccination usually offered (not during pregnancy) |
| Immune (positive) | 10 IU/mL or higher | Protective immunity, no further action needed |
What it is
Rubella IgG is a specific antibody made by the immune system in response to past rubella infection or, far more commonly in the UK, after MMR vaccination. A positive IgG indicates immunity and ongoing protection against rubella. It is distinct from rubella IgM, which indicates current or very recent infection and is not part of routine immunity testing.
Why a clinician would order it
Rubella IgG is most often requested in pre-pregnancy planning so that any non-immune patient can be offered MMR vaccination before conception (the live vaccine is not given in pregnancy). It is also tested in healthcare workers, after exposure to a suspected case, and as part of antenatal serology in some settings.
What your Rubella IgG result means
Laboratory reports use different wording for the same result. Here is what each one means. This is general information, not a personal interpretation: a GMC-registered clinician should review your result against your history.
Rubella IgG reactive / positive / detected
Your blood contains protective rubella antibodies, almost always from past MMR vaccination (or, less commonly in the UK, past infection). "Reactive", "positive" and "detected" all mean the same thing here: you are immune to rubella and protected in any future pregnancy. No further action is usually needed. Most UK labs report immunity at 10 IU/mL or higher.
Rubella IgG non-reactive / negative / not detected
No protective rubella antibodies were found, so you are not currently immune. This is common in people who missed MMR or whose immunity has waned over decades. If you are not pregnant, MMR vaccination is offered and immunity rechecked in 4 to 6 weeks. If you are pregnant, MMR is a live vaccine and cannot be given during pregnancy, so it is deferred until immediately after delivery (with avoidance of anyone with rubella in the meantime).
Rubella IgG equivocal / borderline / indeterminate
Your antibody level sits right on the laboratory cut-off, so the result is neither clearly immune nor clearly non-immune. It is usually treated as non-immune for safety. The lab or clinician typically repeats the test, or offers MMR vaccination (when not pregnant) and rechecks afterwards. An equivocal result is not a sign of active infection.
Rubella IgG abnormal / out of range / flagged
When a result is flagged "abnormal" or "out of range" on a portal, it almost always just means the number sits outside the lab's immunity threshold, in other words non-immune. In the context of a routine immunity check it is not a sign of current rubella infection. Rubella IgM (a different test) is what detects active or very recent infection.
If your level is outside the range
Symptoms of low Rubella IgG
- No symptoms; the implication is lack of protection against rubella if exposed in pregnancy.
What low can indicate. No previous immunity to rubella, either from never being vaccinated or from waning immunity over decades. In a non-pregnant patient, MMR vaccination is offered and immunity is rechecked in 4 to 6 weeks. In a pregnant patient, MMR cannot be given during pregnancy and is deferred until immediately after delivery.
Symptoms of high Rubella IgG
- A positive result is reassuring and carries no symptoms.
What high can indicate. Past rubella infection (rare in the UK MMR era) or successful response to MMR vaccination. The patient is protected for any future exposure including any pregnancy.
Testing tips
No fasting required. If you have recently been given MMR, wait 4 to 6 weeks before testing for immunity to allow IgG to develop. This test does not diagnose current rubella infection: rubella IgM is the test for active infection and is requested separately if clinically indicated.
Sources
UK guidance our clinicians use when interpreting this marker.
This page is general patient information, not personal medical advice. A GMC-registered clinician will review your results and tailor any interpretation to you. See our Editorial Policy for how we write and review content.
Common questions about Rubella IgG
What is a normal Rubella IgG range?
Non-immune (negative or equivocal): less than 10 IU/mL (MMR vaccination usually offered (not during pregnancy)). Immune (positive): 10 IU/mL or higher (Protective immunity, no further action needed). Always interpret your own results against the laboratory range printed on your report, since assay-specific reference ranges vary.
What does a low Rubella IgG result mean?
No previous immunity to rubella, either from never being vaccinated or from waning immunity over decades. In a non-pregnant patient, MMR vaccination is offered and immunity is rechecked in 4 to 6 weeks. In a pregnant patient, MMR cannot be given during pregnancy and is deferred until immediately after delivery.
What does a high Rubella IgG result mean?
Past rubella infection (rare in the UK MMR era) or successful response to MMR vaccination. The patient is protected for any future exposure including any pregnancy.
Do I need to fast or prepare for the Rubella IgG blood test?
No fasting required. If you have recently been given MMR, wait 4 to 6 weeks before testing for immunity to allow IgG to develop. This test does not diagnose current rubella infection: rubella IgM is the test for active infection and is requested separately if clinically indicated.
What does "Rubella IgG reactive / positive / detected" mean?
Your blood contains protective rubella antibodies, almost always from past MMR vaccination (or, less commonly in the UK, past infection). "Reactive", "positive" and "detected" all mean the same thing here: you are immune to rubella and protected in any future pregnancy. No further action is usually needed. Most UK labs report immunity at 10 IU/mL or higher.
What does "Rubella IgG non-reactive / negative / not detected" mean?
No protective rubella antibodies were found, so you are not currently immune. This is common in people who missed MMR or whose immunity has waned over decades. If you are not pregnant, MMR vaccination is offered and immunity rechecked in 4 to 6 weeks. If you are pregnant, MMR is a live vaccine and cannot be given during pregnancy, so it is deferred until immediately after delivery (with avoidance of anyone with rubella in the meantime).
What does "Rubella IgG equivocal / borderline / indeterminate" mean?
Your antibody level sits right on the laboratory cut-off, so the result is neither clearly immune nor clearly non-immune. It is usually treated as non-immune for safety. The lab or clinician typically repeats the test, or offers MMR vaccination (when not pregnant) and rechecks afterwards. An equivocal result is not a sign of active infection.
What does "Rubella IgG abnormal / out of range / flagged" mean?
When a result is flagged "abnormal" or "out of range" on a portal, it almost always just means the number sits outside the lab's immunity threshold, in other words non-immune. In the context of a routine immunity check it is not a sign of current rubella infection. Rubella IgM (a different test) is what detects active or very recent infection.
Can I order a Rubella IgG blood test privately in London?
Yes. WMG Health offers Rubella IgG as part of bespoke panels and several pre-built panels at our 134 Harley Street clinic. Results are clinician-reviewed by a GMC-registered doctor within 4 hours for the most common assays. All panels are custom-built around your specific question; bookings via /contact/ or 020 3239 3378.