What tuberculosis symptoms look like

Tuberculosis (TB) causes a persistent cough that lasts three weeks or longer. The cough often brings up sputum—mucus or phlegm—and may contain blood. You might also run a fever, especially in the afternoon or evening, and wake up drenched in sweat at night. Many people with TB also lose weight and feel exhausted even when they rest.

These symptoms develop slowly over weeks or months, not suddenly like flu. That gradual onset is one reason TB is sometimes missed at first—people assume they have a lingering cold or bronchitis. But if a cough lasts more than three weeks, TB is one of the conditions a doctor will investigate.

Not everyone with TB infection shows symptoms. Some people carry the bacteria but never become sick. Others develop symptoms months or even years after the infection starts. The difference depends on whether your immune system can control the bacteria or whether it spreads in your lungs.

Key Takeaways

  • A cough lasting three weeks or longer, especially one that brings up sputum or blood, is the most common sign of active TB.
  • Fever, night sweats, weight loss, and fatigue often appear alongside the cough and develop gradually over weeks.
  • TB symptoms develop slowly, which is why people sometimes mistake it for a cold or bronchitis until the cough persists.
  • Some people carry TB bacteria without ever feeling sick, while others develop symptoms months after infection.
  • A chest X-ray and sputum test are the standard ways doctors confirm TB when symptoms are present.

The persistent cough and what it means

The cough is almost always the first symptom people notice. It starts dry but usually becomes wet within a few days or weeks, producing mucus. The sputum may be clear, yellowish, or tinged with blood. Some people cough up blood without much mucus—a sign the infection is damaging lung tissue.

Coughing is your lungs' way of clearing the bacteria and inflammation. The longer the infection goes untreated, the more damage occurs, and the cough may worsen. People often describe it as exhausting—it can keep them awake at night or make it hard to catch their breath during the day.

A cough from TB does not respond to over-the-counter cough medicine the way a cold does. If you have been coughing for three weeks and nothing seems to help, that is a signal to see a doctor and mention the duration. Doctors take a three-week cough seriously because it narrows down the list of possibilities.

Fever and night sweats

TB fever is usually low-grade—around 99 to 101 degrees Fahrenheit—and often appears in the afternoon or early evening. It may come and go rather than staying constant. Many people do not realize they have a fever until they take their temperature, because the fever is mild enough that they just feel warm or flushed.

Night sweats are often more noticeable than the fever itself. People wake up soaked through their clothes and sheets, sometimes multiple times a night. The sweating is heavy enough that they need to change clothes or shower. This happens because TB causes inflammation that triggers the body's temperature regulation to go haywire, especially at night when the immune system is most active.

Night sweats combined with a persistent cough is a pattern doctors recognize. If you are waking up drenched and also coughing, mention both symptoms together when you see a doctor—that combination points toward TB more strongly than either one alone.

Weight loss and fatigue

People with active TB often lose weight without trying. The infection causes the body to burn more calories as it fights the bacteria, and many people also lose their appetite. Weight loss can be gradual—a few pounds a month—or more noticeable if the TB goes untreated for a long time.

Fatigue is another hallmark. People feel tired even after sleeping, and simple tasks like climbing stairs or walking to the store feel exhausting. This exhaustion comes from the infection itself and from the body's effort to fight it. It is different from the tiredness of a bad cold—it persists and does not improve with rest alone.

The combination of weight loss, fatigue, and a cough is significant. If you notice you are losing weight, feeling unusually tired, and coughing at the same time, those three things together warrant a doctor's visit. Any one of them could be many things, but the three together narrow the possibilities.

When symptoms mean you need to see a doctor

See a doctor if you have a cough lasting three weeks or longer, regardless of other symptoms. You do not need to wait for fever or weight loss to appear. A persistent cough is reason enough to get checked.

Seek care sooner if you have a cough plus fever, night sweats, or blood in your sputum. If you also know you have been around someone with TB, tell your doctor that when you call or arrive. That information helps them decide how quickly to test you and what tests to order.

If you have TB symptoms and also have HIV, diabetes, or a weakened immune system from another cause, TB can progress faster and cause more damage. Tell your doctor about any other health conditions you have. This helps them understand how urgently to act and what to watch for.

How doctors confirm TB

A doctor will usually start with a chest X-ray. TB typically shows up as a shadow or infiltrate in the upper lobes of the lungs—the part at the top. The X-ray alone cannot confirm TB, because other infections and conditions can look similar, but it narrows things down.

The definitive test is a sputum smear test. You cough up mucus into a cup, and a lab technician looks at it under a microscope for TB bacteria. This test takes a few days for results. A faster test called a nucleic acid amplification test (NAAT) can detect TB DNA in sputum in hours, and many clinics now use this instead of or alongside the smear test.

If the sputum tests are positive, your doctor will send a sample for drug susceptibility testing. This determines which antibiotics will work against your particular TB strain. Some TB bacteria have developed resistance to certain drugs, so knowing which drugs work is essential for treatment.

The difference between TB infection and TB disease

TB infection means you carry the bacteria but do not feel sick and cannot spread it to others. You have no symptoms, and a chest X-ray looks normal. A skin test or blood test shows you have been exposed, but that is all. About 5 to 10 percent of people with TB infection eventually develop TB disease if they do not receive preventive treatment.

TB disease means the bacteria are multiplying in your lungs and causing damage. This is when symptoms appear—the cough, fever, sweats, and weight loss. People with TB disease can spread the infection to others through the air when they cough or sneeze.

The symptoms described in this article apply to TB disease, not TB infection. If you have symptoms, you have moved from infection to disease, and treatment is urgent. If you have no symptoms but a test shows TB infection, your doctor may recommend preventive treatment to stop disease from developing later.

Frequently Asked Questions

Can you have TB without a cough?

TB almost always causes a cough when it becomes active disease. If you have TB bacteria but no symptoms, you have TB infection, not disease. Rarely, TB spreads outside the lungs—to the bones, kidneys, or brain—and may not cause a cough, but this is uncommon and usually happens when lung TB goes untreated for a long time.

How long does it take for TB symptoms to show up?

Symptoms can appear weeks to months after infection, or even years later. Some people develop symptoms within a few weeks of exposure. Others carry the bacteria for years before symptoms appear, often triggered by illness or stress that weakens the immune system. There is no set timeline.

Is TB cough contagious?

Yes. When someone with active TB coughs, sneezes, or speaks, they release tiny droplets containing TB bacteria into the air. People nearby can breathe these in and become infected. The risk is highest with prolonged close contact—living in the same home or working in the same small space for hours.

Can TB cause chest pain?

Chest pain is not a typical early symptom of TB, but it can develop if the infection spreads to the lining of the lungs or if a cavity forms in lung tissue. If you have chest pain along with a persistent cough, mention both to your doctor, as it may indicate more advanced disease.

What if I have symptoms but a TB test comes back negative?

A negative test does not always rule out TB, especially early in infection or if the sputum sample was not collected properly. If you have symptoms and a strong reason to suspect TB, your doctor may repeat the test or order additional imaging. Other conditions—like fungal infections or lung cancer—can cause similar symptoms.