A blood test can determine if you have had a recent or past infection, or if you have never been exposed to the rubella virus. People with recent infection or vaccination will have a positive IgM antibody and those with a past infection (and those who have been vaccinated for rubella) will have a positive IgG antibody. Neither antibody will be present if there has been no contact with the virus or vaccine. A blood test for both antibody types will help the doctor predict if you are protected from infection or if you are at risk.
 

If you are pregnant and have exposure to a person with a rubella-like rash and flu-like symptoms or you develop a rash and symptoms, your doctor should request a laboratory test to help diagnose possible rubella infection. It is a particularly important to test for rubella in early pregnancy as infection during the first 16 weeks of pregnancy presents major risks for the unborn baby. Antibody testing is strongly recommended for women planning a pregnancy so those who are not immune to the virus can be vaccinated before they conceive. Antibody testing is often used in infants born with abnormalities, such as deafness, mental retardation, heart defects, and cataracts that may have resulted from a rubella infection acquired before their birth.
Testing for rubella antibody is not usually done on children or adults who were vaccinated to prove the vaccine was effective.

In an adult or child, the absence of IgG antibodies to rubella means the person is not immune. Absence of IgM antibodies and presence of IgG antibodies indicates a history of past exposure to the virus or vaccination. Presence of IgM antibodies with or without IgG antibodies usually represents recent infection. In an infant the presence of IgM antibodies means the baby was infected during the pregnancy. Occasionally, low levels of IgM antibodies represent a false positive result. A positive IgM result, particularly in pregnancy, needs to be interpreted with care.
Oral secretions or a throat swab are tested by a different technique looking for the presence of rubella virus, not the body's response to infection.

If only a low level of antibodies are detected then the test may be inconclusive, and immunisation with the rubella vaccine may be recommended as a precaution.
In addition to antibody tests, the evidence of recent rubella infection is a positive viral culture for rubella or detection of rubella virus by testing for the genetic material (RNA) of the rubella virus in a body fluid sample, such as a throat swab. Because these procedures are complex, time-consuming and expensive, most diagnostic laboratories refer this testing to a reference laboratory.

The rubella vaccine should not be given to a pregnant woman, and a woman should avoid getting pregnant for one month after taking the vaccine.

The vaccine contains a live virus that has been altered so it cannot cause all the problems associated with a natural infection. The most common side-effects are pain at the site of injection, fever, swollen glands or a rash following immunisation. Young children have a slightly increased risk of febrile convulsions up to 2 weeks following vaccination. Adults in particular may develop transient pain in their joints, especially their hands and wrists. There is no credible evidence linking the measles, mumps, rubella (MMR) vaccine to autism.

There is no antibiotic or anti-viral drug that can prevent or ‘cure’ the infection or reduce the risk of rubella to an unborn baby. Specialist advice is essential.

If you are going to have symptoms, the rash usually begins 15–17 days after coming in contact with an infectious person, but it may take as long as 3 weeks