The main signs of active tuberculosis

If you have active tuberculosis (TB), you will most likely develop a cough that lasts more than three weeks. This is the single most common symptom. The cough may start dry and then produce mucus or phlegm, sometimes with blood in it. You may also cough up blood without much mucus.

Along with the cough, you may feel chest pain or discomfort when you breathe or cough. You might also notice you are sweating heavily at night, even when your bedroom is cool. These night sweats can be so heavy that you wake up with damp sheets and clothes. At the same time, you may lose weight and appetite without trying to diet, and you may feel tired and weak even when you are resting.

A fever is also common with active TB, though it is often mild — usually between 99 and 101 degrees Fahrenheit — and may be worse in the afternoon or evening. Some people have chills along with the fever.

Key Takeaways

  • A cough lasting longer than three weeks, especially one that produces mucus or blood, is the most common sign of active tuberculosis.
  • Night sweats, unexplained weight loss, fatigue, and a mild fever are typical symptoms that often appear alongside the cough.
  • Chest pain when breathing or coughing can occur if the infection has reached the lining around your lungs.
  • You should see a doctor if you have a cough lasting more than three weeks, even if you do not have other symptoms.
  • A skin test or blood test can show whether you have TB infection, and a chest X-ray can show whether the disease is active in your lungs.

When to see a doctor

You should contact a doctor if you have had a cough for more than three weeks. This is true even if you feel otherwise well or if you do not have a fever. A cough that lasts this long is not normal and warrants a medical evaluation.

You should also see a doctor right away if you cough up blood, have chest pain when you breathe, or are sweating heavily at night. If you have been in close contact with someone who has active TB — such as a family member, coworker, or someone you live with — tell your doctor about that contact even if you do not have symptoms yet. People who have been exposed may develop symptoms weeks or months later.

How doctors test for tuberculosis

Your doctor will start by asking about your symptoms, how long you have had them, and whether you have been around anyone with TB. They will listen to your lungs with a stethoscope to check for abnormal sounds.

To confirm TB, your doctor will order one or more tests. The most common is a skin test (also called a Mantoux test or tuberculin skin test), in which a small amount of fluid is injected just under the skin on your forearm. You return 48 to 72 hours later, and the doctor measures any swelling at the injection site. A raised bump of a certain size means you may have TB infection.

Your doctor may also order a blood test that looks for TB antibodies or TB proteins in your blood. Blood tests are faster than skin tests — you get results within a few days — and they are not affected by certain vaccines or skin conditions.

If the skin test or blood test is positive, your doctor will order a chest X-ray to see whether TB is active in your lungs. The X-ray shows whether there is damage or scarring in the lungs. If the X-ray shows signs of active TB, your doctor may also ask you to provide sputum samples (mucus you cough up) so they can test it for TB bacteria and check which medicines will work best against your infection.

The difference between TB infection and active TB disease

It is important to understand that a positive TB test does not always mean you have active TB disease. You could have latent TB infection, which means TB bacteria are in your body but your immune system is keeping them inactive. People with latent TB do not have symptoms, cannot spread TB to others, and may never develop active disease.

However, people with latent TB infection can develop active TB disease later, especially if their immune system becomes weakened by illness, age, or certain medicines. Your doctor will determine whether you have latent or active TB based on your symptoms, chest X-ray results, and sputum tests.

If you have latent TB, your doctor may recommend preventive treatment with medicine to lower the risk that you will develop active disease in the future. If you have active TB, you will need a course of antibiotics lasting several months.

Symptoms that may look like TB but are not

A long-lasting cough can have many causes other than TB. Chronic bronchitis, asthma, pneumonia, whooping cough, and even acid reflux can cause a cough that lasts weeks. Smoking and exposure to secondhand smoke are also common causes of persistent cough.

Weight loss, night sweats, and fatigue can be signs of many conditions, including diabetes, hyperthyroidism, lymphoma, and other infections. A mild fever can accompany a cold, flu, or sinus infection. The only way to know whether your symptoms are caused by TB is to be tested by a doctor.

What happens after a TB diagnosis

If your doctor confirms you have active TB, you will start a course of antibiotics. The standard treatment uses four medicines taken together for the first two months, then two medicines for the remaining four months. It is important to take all the medicines exactly as prescribed, even after you start feeling better, because stopping early can allow the bacteria to develop resistance to the drugs.

Your doctor will monitor your progress with follow-up visits and may repeat chest X-rays or sputum tests to make sure the treatment is working. Most people with active TB stop being contagious after about two weeks of treatment, though they must continue taking medicine for the full course.

If you have latent TB infection, your doctor may prescribe a preventive medicine regimen that can last from a few months to a year, depending on which medicine is used. Taking preventive medicine significantly lowers your risk of developing active TB disease.

Frequently Asked Questions

Can you have tuberculosis without a cough?

TB usually causes a cough, but some people have active TB that affects other parts of the body — such as the bones, kidneys, or lymph nodes — rather than the lungs. These forms of TB may not cause a cough. If you have night sweats, weight loss, and fever without a cough, mention this to your doctor, especially if you have been exposed to TB.

How long does it take to get TB test results?

A skin test requires two visits: you get the injection at the first visit and return 48 to 72 hours later for the reading. A blood test usually gives results within a few days. If either test is positive, a chest X-ray follows, which is done the same day or within a few days.

If I have a cough for three weeks, do I definitely have tuberculosis?

No. Many conditions cause a cough lasting three weeks or longer, including bronchitis, asthma, pneumonia, and smoking-related lung disease. A cough lasting this long does warrant a doctor's visit, but your doctor will run tests to determine the actual cause.

Can you spread tuberculosis if you do not have symptoms?

No. If you have latent TB infection, you cannot spread TB to anyone else. Only people with active TB disease in the lungs can spread the infection, usually through coughing or sneezing. Most people stop being contagious after about two weeks of antibiotic treatment.