Tuberculosis: Causes, Symptoms, Diagnosis and Treatment

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Tuberculosis (TB) is an infection of the lungs that you can get from breathing in germs from an infected person. You may notice you’ve been coughing a lot recently, coughing up blood, sweating at night, and losing weight without trying. But, even so, many people who have TB don’t know it because they don’t have any symptoms or they have symptoms common to other health conditions. It is important to see a doctor for this condition even if you don’t have symptoms because it can get worse later in life and be fatal if untreated. Read on to learn more about TB and what to do if you have it.

What Is Tuberculosis?

TB is an infection of the lungs with a germ (Mycobacterium tuberculosis, or M. tuberculosis). This bacterium infects your lungs if you breathe it in, but it can also spread to infect other organs in your body.

There are different ways that doctors classify and manage TB infection in the lungs. First, when exposed to TB, you get primary TB which can have symptoms of active lung infection. Then the infection becomes latent, and you don’t have symptoms during this time even though the infection still lives in your lungs. This is called latent tuberculosis infection (LTBI). Then after years of having LTBI, your TB can be reactivated if you experience immunocompromise or a weakened immune system. When your TB is reactivated, you’ll have symptoms of active lung infection. 

Signs and Symptoms of Tuberculosis

If you have TB, the main symptoms you may have include: 

  • Having a cough that lasts three weeks or more
  • Coughing up blood
  • Excessive sweating at night
  • Unintentional weight loss

Other symptoms you may have with your TB infection can include:

  • Chest pain, especially with breathing or coughing
  • Tiredness
  • Fever
  • Chills
  • Loss of appetite

TB can also affect other organs in your body, including your spine, heart, kidneys, or brain. When this occurs, it’s referred to as extrapulmonary tuberculosis. TB that affects your spine can cause back pain. When it affects your heart, it can cause your heart to swell and prevent it from pumping effectively. If it affects your kidneys, it can cause blood in your urine. If it affects your brain, you can get meningitis or swelling of the brain and the membranes surrounding it.

Causes of Tuberculosis

What causes TB? You can get TB when someone with active TB releases respiratory droplets that contain the bacteria that cause TB into the air, and you breathe them in. Someone with active TB may spread these droplets by coughing, sneezing, laughing, spitting, or speaking.

There are several risk factors for TB:

  • Conditions that weaken the immune system, like HIV/AIDS, cancer, diabetes, lung disease, severe kidney disease, low body weight, or substance abuse issues
  • Close contact with those infected with TB
  • Homelessness
  • Taking immunosuppressing medications after having an organ transplant
  • Recent travel to or residence in countries with high rates of TB, like India, China, Indonesia, and the Philippines
  • Use of certain medications, like corticosteroids (drugs that suppress the immune system) and specialized treatments for arthritis or Crohn’s disease
  • Work or residence in institutions with a high risk of tuberculosis infection, such as hospitals, homeless shelters, correctional facilities, nursing homes, and residential homes for people with HIV

Diagnostic Tests

Your doctor can test for TB with a skin or blood test.

TB Skin Test

In the skin test (TST test), your doctor will inject a modified form of M. tuberculosis under your skin. You’ll see a small bump under the skin, which is normal. 

Over the next few days, you will need to look for whether that injection site becomes red and swollen. You’ll return to your doctor’s office 2-3 days later for them to check the injection site, but if you have a serious reaction, you should return sooner. The size of the swelling and redness, in combination with certain risk factors, determines whether your test is positive or not. This test isn’t perfect, and there’s a chance you could get a false positive or a false negative result.

You may get a false positive skin test if you:

  • Have received the BCG vaccine – which children in some countries like India receive
  • Got infected with bacteria in the same family as M. tuberculosis

You may get a false negative skin test if you:

  • Have low levels of a type of immune cell called a T-cell
  • Are younger than six months old
  • Have recovered from 
  •  Recovered by TB in the past eight to 10 weeks
  • Recently received measles or smallpox vaccination

TB Blood Test

In the TB blood test( QuantiFERON or SPOT TB), your doctor takes a sample of your blood to see if there is M. tuberculosis in your body. While the standard testing used to be the TST skin test, many doctors now prefer to use the TB blood test. It requires only one visit, the results are available faster, and it does not give a false positive for people who had the BCG vaccine in childhood. If you get a TB blood test at your doctor’s office, the results will come back just like any other bloodwork. If you see the results in your online medical chart before your doctor calls you, you should reach out to discuss the results with them.

X-Ray and Sputum Sample

Neither the skin nor the blood test can tell the difference between latent and active tuberculosis infection. Your doctor will use chest X-rays or a sample of sputum, or phlegm, to tell the difference between the two. Your chest X-ray will look normal if you have LTBI. If you have active TB, your chest X-ray will show what looks like white, fluffy clouds in your lungs. Similarly, your phlegm will look normal if you have LTBI. If you have active TB, on the other hand, your phlegm will have M. tuberculosis germs in it that can be identified with certain laboratory tests.



If you have LTBI, it is important that you receive treatment. Even though you don’t feel sick and can’t pass TB onto other people, LTBI can progress to an active infection. In fact, 1 in 10 people with LTBI develops an active infection. Your doctor will treat you with one or a combination of the medications isoniazid, rifapentine, and rifampin. Depending on which drug or combination of drugs your doctor determines is best for you, the treatment can last between three and nine months. This is a difficult infection to treat, and it’s important that you take all of the medication as prescribed to avoid growing drug-resistant TB, which is more difficult to treat and more deadly. If you have concerns about your ability to take all of your TB medications as prescribed, talk to your doctor about finding a plan that works for you.

Active Tuberculosis

For active TB, there are several treatment regimens your doctor can give you. Medications used to treat active TB include rifapentine, isoniazid, pyrazinamide, ethambutol, and moxifloxacin. Because this infection is active and causing symptoms, it requires more medications and longer treatment. As with LTBI, it’s important that you find a treatment plan that you can stick to and follow every day to prevent the infection from getting worse. 

Next Steps: Tuberculosis Prevention

Avoid Infected People: To prevent getting TB, avoid people who have TB. If you’re traveling to countries with high rates of TB, avoid settings where TB is common, like hospitals, prisons, or homeless shelters.

Vaccine: There is a vaccine against TB called the Bacille Calmette-Guérin (BCG) vaccine. It is not typically used in the U.S. However, it is commonly given to infants and children in countries where TB is common. The vaccine does not always protect you against TB, but your doctor may recommend it depending on your risk factors.

Take LTBI Medication: If you have LTBI, take your medications as instructed to avoid getting an active tuberculosis infection.

When To See a Doctor

Talk to your doctor if you’ve been exposed to TB or are having symptoms of TB. Treatment regimens for TB are difficult to keep up with, but it is important to take all your medication as prescribed to ensure you get treated completely. As you’re taking your medications, it may help you to learn more about other people’s struggles with TB. Learn more about people’s personal stories with TB  here

Resource Links:

  1. “Tuberculosis” via Mayo Clinic
  2. “Tuberculosis” via WHO
  3. “TB Elimination: Interferon-Gamma Release Assays (IGRAs) – Blood Tests for TB Infection” via CDC
  4. “Tuberculosis (TB)” via CDC
  5. “Tuberculosis” via StatPearls 
  6. “Extrapulmonary tuberculosis” via BMJ Best Practice
  7. “Is it time to replace the tuberculin skin test with a blood test?” via JAMA