The TB Skin Test
How do I know if I have TB infection?
A skin test is the only way to tell if you have latent TB infection. This test is usually done on the forearm. A small needle is used to inject testing material, called tuberculin, under the skin. In two or three days, a health worker will check to see if there is a reaction to the test.
The test may be "positive" if a bump appears on your arm. This bump means you may have latent TB infection, depending on its size and your risk factors for TB exposure. You may need medicine to keep from getting sick.
Note: If you have ever had a "positive" reaction to a TB skin test or if you have been treated with TB drugs in the past, tell the health worker.