Skip to content

Latent Tuberculosis

What is latent TB infection?

Latent TB, also known as “sleeping” TB (BC Centre for Disease Control, 2015), occurs when TB bacteria are breathed in, but the body is able to prevent the bacteria from growing. Although the bacteria may be sleeping now, they can become active later.

People with latent TB infection:

  • Have no symptoms
  • Don’t feel sick
  • Can’t spread TB to others
  • Usually have a positive skin test reaction
  • Can develop active TB disease if they do not receive treatment for latent TB infection – especially people who have weak immune systems

What do I do if I have latent TB infection?

Your doctor may recommend medication to reduce the chances of TB infection progressing to TB disease. Taking antibiotic treatment for 6–9 months can protect you from developing TB disease in the future. It is important to take all your medication as prescribed by your doctor. TB drugs are provided free of charge from the Leeds, Grenville and Lanark District Health Unit.

Is the treatment safe?

Most people complete the treatment without problems, but these drugs may harm the liver. Call your doctor immediately if you have any of these symptoms:

  • Loss of appetite
  • Feel sick to your stomach
  • Rash
  • Itching
  • Brown or dark urine
  • Yellowish skin or eyes
  • Stomach pain or discomfort
  • Fever

People who drink heavily or have hepatitis may already have weak livers. Your doctor can order a blood test to see if your liver has been affected. If you develop liver problems, stopping the medication will allow the liver to heal itself. It is always best not to drink alcohol if you are taking TB drugs.


BC Centre for Disease Control. “TB Germ: A cunning World Traveller.” February 23, 2015.

Centers for Disease Control and Prevention. “Questions and Answers about TB.” December 18, 2014.