The main ways to reduce your TB risk

Tuberculosis spreads through the air when a person with active TB disease coughs, sneezes, or speaks. You reduce your risk by limiting exposure to people with untreated TB, getting tested if you've been exposed, and taking preventive medication if you carry the TB bacteria. Most people who breathe in TB bacteria never develop the disease—your immune system usually stops it. The people at highest risk are those with weakened immunity, close contacts of someone with active TB, and people living in crowded settings with poor ventilation.

Prevention has two parts: keeping yourself from catching TB in the first place, and if you do carry the bacteria, preventing it from becoming active disease. Both are achievable with straightforward steps.

Key Takeaways

  • TB spreads through the air, so avoiding prolonged close contact with untreated TB patients is the primary prevention method.
  • If you've been exposed to someone with active TB, a skin test or blood test can show whether you carry the bacteria.
  • People who carry TB bacteria but have no symptoms can take preventive medication to stop the disease from developing.
  • Maintaining good nutrition, managing stress, and treating conditions like HIV or diabetes strengthens your immune system against TB.
  • Proper ventilation and respiratory protection in healthcare or high-risk settings reduces transmission risk.

Avoiding exposure to active TB disease

The most direct prevention is avoiding prolonged contact with people who have untreated active TB. TB spreads through airborne droplets, not through touching, sharing food, or shaking hands. You're at risk mainly if you spend hours in a poorly ventilated space with someone who is coughing and has not yet started treatment.

If someone in your household or workplace has active TB, they should isolate until they've been on medication for at least two weeks—at that point they're no longer contagious. If you work in healthcare, corrections, or homeless shelters, ask your employer about respiratory protection (N95 masks) and whether you need baseline TB testing. Rooms where TB patients are treated should have negative air pressure and good ventilation to prevent the bacteria from spreading to others.

Getting tested after exposure

If you've spent significant time near someone with active TB—a family member, coworker, or close contact—you should be tested. Two types of tests can detect TB bacteria: a tuberculin skin test (also called a Mantoux test), where a small amount of TB protein is injected under the skin and read 48 to 72 hours later, and an interferon-gamma release assay (IGRA), a blood test that shows whether your immune system has encountered TB bacteria.

The skin test is less expensive and widely available; the blood test is faster and more specific in certain populations. Either test can show whether you carry TB bacteria, but neither distinguishes between latent infection (bacteria present but dormant) and active disease. If your test is positive, a chest X-ray will determine whether you have active TB or latent TB infection. Testing should happen within 8 to 10 weeks of exposure, though some people may need retesting if they were tested too soon after exposure.

Taking preventive medication if you carry TB bacteria

If you test positive for TB bacteria but have no symptoms and a normal chest X-ray, you have latent TB infection. Without treatment, about 5 to 10 percent of people with latent TB will develop active disease at some point in their lives. Preventive medication reduces that risk to less than 1 percent. The standard regimen is isoniazid, taken daily for 6 to 9 months, though shorter courses using different drug combinations are also available.

Preventive medication is especially important if you have a weakened immune system (from HIV, immunosuppressive drugs, or certain medical conditions), are a close contact of someone with active TB, or have recently converted from a negative to positive TB test. Your doctor will check your liver function before starting medication, since isoniazid can affect the liver. You'll have follow-up visits to monitor for side effects and ensure you're taking the medication as prescribed. Completing the full course is critical—stopping early leaves you at risk for active disease.

Strengthening your immune system

Your immune system is your best defense against TB bacteria. People with weakened immunity—from HIV, diabetes, kidney disease, malnutrition, or immunosuppressive medications—are much more likely to develop active TB if exposed. If you have HIV, maintaining an undetectable viral load through antiretroviral therapy dramatically reduces TB risk. If you have diabetes, keeping blood sugar controlled helps your immune system fight infection.

Nutrition matters: adequate protein, calories, and micronutrients (especially vitamin B6, which isoniazid depletes) support immune function. If you smoke, quitting reduces your risk—smoking damages the lungs' ability to clear bacteria. Chronic stress and poor sleep also weaken immunity, so managing stress and getting adequate rest are part of prevention. If you have a condition that affects immunity, work with your doctor to keep it well-controlled.

TB prevention in high-risk settings

Healthcare workers, people in correctional facilities, and staff in homeless shelters face higher TB exposure. Healthcare facilities should have infection control protocols: negative-pressure isolation rooms for TB patients, respiratory protection for staff entering those rooms, and regular TB screening for employees. Workers should know the symptoms of active TB and report them promptly.

In congregate settings like shelters or prisons, TB spreads more easily because of crowding and poor ventilation. Prevention includes baseline TB testing for all residents or staff, prompt isolation of anyone with symptoms, and improved ventilation where possible. People in these settings who test positive for latent TB should be offered preventive medication. Employers in high-risk settings should have written TB control plans and train staff on transmission and prevention.

What to do if you develop TB symptoms

Prevention sometimes fails, and you develop active TB disease. The sooner you seek care, the sooner you can start treatment and stop spreading the disease to others. Symptoms include a cough lasting more than three weeks, chest pain, coughing up blood, fever, night sweats, and weight loss. If you have these symptoms, see a doctor and mention that you may have been exposed to TB or that you carry TB bacteria.

Active TB is treatable with a standard four-drug regimen taken for 6 months. You're no longer contagious after about two weeks of treatment, so isolation can end. Completing the full course is essential—incomplete treatment leads to drug-resistant TB, which is much harder to cure. Your doctor will monitor your progress with follow-up X-rays and sputum tests.

Frequently Asked Questions

Can I catch TB from someone who is on treatment?

No. People with active TB become non-contagious within about two weeks of starting appropriate medication. If someone tells you they're being treated for TB, there's no risk from casual contact. The danger is from untreated active TB or from people who don't know they have it yet.

Do I need a TB test if I've been vaccinated with BCG?

Yes. The BCG vaccine, given in many countries outside the United States, provides some protection but is not fully reliable. If you've had BCG and are exposed to active TB, you should still be tested. A positive skin test after BCG vaccination may be harder to interpret, which is why a blood test (IGRA) is sometimes preferred for vaccinated people.

How long does preventive medication take to work?

Preventive medication reduces your risk of developing active TB, but it doesn't work instantly. You need to complete the full course—usually 6 to 9 months—to get the maximum benefit. Even after finishing, your risk remains very low for the rest of your life.

What if I'm pregnant and exposed to TB?

Pregnant people can be tested for TB and can take preventive medication if needed. Isoniazid is considered safe during pregnancy. Untreated TB infection poses a greater risk to you and your baby than preventive medication does, so discuss testing and treatment with your doctor.

Can I prevent TB if I live with someone who has active disease?

Yes, but you need to act quickly. Ask the person to isolate in a separate room with good ventilation until they've been on medication for two weeks. Get tested yourself within 8 to 10 weeks. If your test is positive, start preventive medication. Wear an N95 mask when you must be in the same room before they've completed two weeks of treatment.