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Am Fam Physician. 2000;61(9):2681-2082

See related article on tuberculosis.

What is TB?

Tuberculosis (say: too-burr-cue-low-sis), or TB for short, is an infection caused by a bacteria (a germ). TB usually affects the lungs, but it can spread to the kidneys, bones, spine, brain and other tissues.

What's the difference between TB infection and TB disease?

People with TB infection have the TB bacteria in their body, but they don't have signs of the infection.

People with TB disease (also known as active TB) have disease signs. They may have a cough that doesn't go away. When they cough, they may bring up mucus with blood in it. Or they may have a “dry” cough (no mucus). They may lose weight and feel tired.

Over time, TB infection can become active TB. If you have active TB, you need to be treated quickly so that you get better and don't pass the disease to others.

How is TB spread?

When people with active TB cough, they release bacteria into the air. Other people breathe in the bacteria and may become infected.

Anyone can get TB, but your risk of getting TB is greater if you:

  • Live with a person who has active TB.

  • Have HIV infection.

  • Abuse drugs.

  • Are elderly.

  • Are a health care worker in close contact with people who have TB.

  • Recently moved here from an area where TB is common, such as Africa, Asia or Latin America.

  • Have a chronic illness like diabetes, cancer or kidney disease.

How can I tell if I have TB infection?

See your doctor if you have any of the risk factors listed above. Your doctor will use a TB skin test, called a PPD test, to find out if you have TB infection.

How does the TB skin test work?

Fluid is injected under the skin on your arm with a needle. Two or three days later, your arm is checked. If you have a raised red area or bump where the fluid was injected, the test is “positive.”

Not all people with a positive skin test have TB infection. If your test is positive, you will have a chest x-ray to look for TB in your lungs.

How is TB treated?

TB infection is most often treated with a medicine called isoniazid (say: eye-so-nye-ah-zid). Its usual brand name is INH. Taking a full course of INH greatly lessens your chance of getting active TB. Most adults can be cured by taking one INH pill every day for 9 months.

People with certain health conditions may be given other medicines and may be treated for a different period of time.

Does INH have side effects?

Isoniazid is usually very safe, but it can cause nerve or liver damage in some people. If you are at risk for these problems, your doctor might want to see you often and do some blood tests while you are taking isoniazid.

Tell your doctor if you are taking other medicines. You can reduce your risk of side effects during isoniazid treatment by avoiding alcohol and certain medicines, such as acetaminophen (brand name: Tylenol).

What is drug-resistant TB?

The usual medicines for treating TB infection, like isoniazid, do not work against some kinds of TB bacteria. These bacteria are called “drug-resistant TB.” If your doctor thinks that you have been exposed to drug-resistant TB bacteria, you will need to take different medicines. Not taking medicine as prescribed is the way most people get drug-resistant TB.

How can I make sure that my treatment for TB infection works?

It is important to take every dose of TB medicine as prescribed. To remember to take your medicine, you might set a watch alarm or put the medicine bottle next to your toothbrush. If you still have trouble remembering, your doctor might ask a nurse to help you.

If at any time you are worried that you are having side effects from your medicine, call your doctor right away, but don't stop taking the medicine.

More Information About TB

In addition to your doctor, here are two good sources of information about TB:

Centers for Disease Control and Prevention

  • 1600 Clifton Road

  • Atlanta, GA 30333

  • Phone number: 1-800-311-3435

  • Web address:

National Jewish Medical and Research Center

  • 1400 Jackson Street

  • Denver, CO 80206

  • Phone number: 1-800-222-5864 (for information)

  • E-mail address: lungline@njc

  • Web address:

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