A rubella blood test shows if your body's immune system has made antibodies to help kill the rubella virus. These antibodies stay in the bloodstream for years. Antibodies are made if you have been infected or if you have been vaccinated against the disease.
A rubella test is usually done for someone who is or wants to become pregnant to see if they are at risk for rubella. Rubella (also called German measles or 3-day measles) usually doesn't cause long-term problems. But someone infected with the rubella virus during pregnancy can pass the disease to the baby (fetus), and it can cause birth defects. Miscarriage and stillbirth are also risks for those who are pregnant. Being vaccinated to prevent rubella protects against these complications.
Why It Is Done
A test for rubella is done to find out if:
- Someone who is or wants to become pregnant has antibodies to prevent getting a rubella infection.
- Someone has immunity from a past infection or from being vaccinated.
- Health professionals who are in contact with pregnant people have had rubella. A health professional who has not had rubella may need to be vaccinated to prevent the risk of spreading rubella to someone who is pregnant.
Some babies born with birth defects may be tested for congenital rubella.
How To Prepare
In general, there's nothing you have to do before this test, unless your doctor tells you to.
How It Is Done
A health professional uses a needle to take a blood sample, usually from the arm.
How It Feels
When a blood sample is taken, you may feel nothing at all from the needle. Or you might feel a quick sting or pinch.
Risks
There is very little chance of having a problem from this test. When a blood sample is taken, a small bruise may form at the site.
Results
Each lab has a different range for what's normal. Your lab report should show the range that your lab uses for each test. The normal range is just a guide. Your doctor will also look at your results based on your age, health, and other factors. A value that isn't in the normal range may still be normal for you.
Positive
- A positive rubella IgG antibody test result is good. It means that you are immune to rubella and cannot get the infection. This antibody test is the most common rubella test done.
Negative
- A negative test result means that you aren't immune to rubella. If you are thinking about getting pregnant, talk with your doctor about getting a rubella vaccine at least 4 weeks before you become pregnant.
A different rubella antibody blood test for IgM antibodies is done only if the doctor thinks that you have a current rubella infection.
Credits
Current as of: February 11, 2026
Author: WebMD Ignite Staff
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All WebMD Ignite education is reviewed by a team that includes physicians, nurses, advanced practitioners, registered dieticians, and other healthcare professionals.
