Key points
- There are two types of tests for tuberculosis (TB) infection: the TB blood test and the TB skin test.
- A positive test result for TB infection means you have TB germs in your body.
- If you test positive for TB infection, your health care provider will do other tests to determine if you have inactive TB (also called latent TB infection) or active TB disease.
Why get tested
Getting tested and treated for TB can protect yourself, your family and friends, and your community.
You may need a TB test if you have:
- Symptoms of TB disease
- Spent time with someone who has active TB disease
- Factors that put you at higher risk of developing active TB disease
- Employment, school, travel, or immigration health screening requirements
You may need a TB test even if you do not feel sick. TB germs can live in your body for years without making you feel sick. This is called inactive TB. People with inactive TB do not feel sick and cannot spread TB germs to others.
Who should be tested
If you are at higher risk of being infected with TB germs, you should get tested.
You have a higher risk of being exposed to TB germs if you:
- Were born in or frequently travel to countries where TB is common, including some countries in Asia, Africa, and Latin America
- Live or used to live in large group settings where TB is more common, such as homeless shelters, prisons, or jails
- Recently spent time with someone who has active TB disease
- Work in places where TB is more likely to spread, such as hospitals, homeless shelters, correctional facilities, and nursing homes
Some people who have inactive TB never develop TB disease, and others with inactive TB develop active TB disease months or even years later when their immune system can no longer keep the TB germs from multiplying and growing in the body.
Anyone can get TB, but some people who have inactive TB are more likely to develop TB disease than others.
You have a higher risk of developing TB disease once infected if you:
- Have a weaker immune system because of certain medications or health conditions such as diabetes, cancer, or HIV
- Became infected with TB germs in the last two years
- Are a baby or young child, especially under five years of age
- Inject illegal drugs
- Are sick with other diseases that weaken the immune system
- Are elderly
- Were not treated correctly for TB in the past
TB tests are generally not needed for people with a low risk of infection with TB germs.
Types of tests
There are two types of tests for TB infection: the TB blood test and the TB skin test. Ask your health care provider which TB test is best for you.
TB blood test
TB blood tests (also called interferon-gamma release assays or IGRAs) use a blood sample to find out if you are infected with TB germs. The tests measure how your immune system reacts when a small amount of your blood is mixed with TB proteins.
Tell your health care provider if you received a TB vaccine
Many people born outside the United States have received the TB vaccine (also known as Bacille Calmette-Guérin or BCG).
TB blood tests are the preferred test for people who have received the TB vaccine. Unlike the TB skin test, TB blood tests are not affected by BCG vaccination.
TB skin test
For the TB skin test, a health care provider uses a small needle to put some testing material under the skin. You will need to return to your health care provider in two to three days to see if there is a reaction.
Other tests may be needed
Your health care provider will do other tests to determine if you have inactive TB or active TB disease if you have a:
- Positive TB blood test or TB skin test result
- Negative TB blood test or TB skin test result, but you have symptoms of active TB disease
These tests may include a chest x-ray, and a test of the sputum (phlegm) you cough up.
How to get tested
You can get tested for TB at the health department or at your health care provider's office. Your health care provider will choose the TB test that is best for you. Public and private health care plans may cover TB testing costs.
Finding a test location
Understanding TB blood test or TB skin test results
A positive test result for TB infection means you have TB germs in your body. Your health care provider will do other tests to determine if you have inactive TB or active TB disease. These tests may include a chest x-ray, and a test of the sputum (phlegm) you cough up.
A negative test result for TB infection means inactive TB or active TB disease is unlikely, but your health care provider may do more tests, especially if:
- You have symptoms of active TB disease, like coughing, chest pain, fever, weight loss, or tiredness.
- You have HIV.
- You were recently exposed to TB germs.
What to do if you've tested positive
If your TB blood test or TB skin test is positive, you have TB germs in your body. Your health care provider will do other tests to determine if you have inactive TB or active TB disease.
Keep a record of your positive test result
Once you have a positive TB blood test or TB skin test result, you may still have a positive test result on future TB tests. This includes even after you finish taking all of your TB medicine for inactive TB or active TB disease.
Ask your health care provider for a written record of your positive TB test result. This will be helpful if you are asked to have another TB test in the future.
Resources
What You Need to Know About Tuberculosis Fact Sheet
Questions and Answers About Tuberculosis Booklet
What You Need to Know About the TB Skin Test Fact Sheet