Information for people who have been ​prescribed a course of medication to prevent tuberculosis​.

Last updated: 25 June 2014

Your doctor has prescribed you a course of medication to prevent tuberculosis (TB).

This treatment is offered because you have either:

  • a positive tuberculin skin test (also called a TST or Mantoux test) or
  • an abnormal chest x-ray, or
  • have been in contact with someone who has infectious TB.

These things indicate that you are likely to have TB infection that could develop into TB disease.

What is the difference between TB infection and TB disease?

TB infection

  • A positive TST indicates TB infection.
  • When a person has TB infection the TB germs are in the body, but they are not active and cannot be spread to other people.
  • In most cases (90-95% of people), the body's immune system controls the germs and TB disease will not develop.
  • People with TB infection alone have no symptoms and feel well.

TB disease

  • In about 5-10% of people with TB infection, TB disease can develop, when inactive TB germs become active and multiply.
  • This can happen even after many years, usually when the body’s immune system is weakened. This may be because of ageing, serious illness, drug or alcohol use, HIV infection (the virus that causes AIDS), or other conditions.

TB infection

  • Inactive TB germs in the body
  • No symptoms of TB
  • Cannot spread TB germs to others
  • May need treatment for TB infection to prevent progression to TB disease

TB disease

  • Active TB germs in the body
  • Symptoms of TB such as coughing, fever, weight loss
  • May spread TB germs to others
  • Must have treatment to cure TB disease

What is the treatment for TB infection?

  • The usual medication given to prevent TB is isoniazid, although other medications can be used.
  • These medications are taken daily for at least 6 months, as it takes this long to kill the inactive TB germs.
  • You may be given pyridoxine (Vitamin B6) to prevent possible side effects of Isoniazid.

I don't feel sick, do I need to take medication?

  • Even though you don't feel sick, treating TB infection at an early stage can kill the TB germs present in your body, and help prevent you from developing TB disease.
  • Treatment for TB infection can help prevent TB disease in the majority of people who complete the full course of medication.

Is the treatment for TB infection safe?

  • These medications are safe and most people (including children) experience no problems when taking them.
  • Some people may have side effects including:
    • stomach pain
    • yellow skin or eyes
    • dark urine (like black tea or coffee)
    • loss of appetite
    • nausea or vomiting
    • rash or itchiness
    • fever
    • severe tiredness
    • tingling in the fingers or toes

Please inform your doctor or nurse straight away if you get any of these symptoms or other symptoms that you are worried about. A very rare but serious side effect is liver failure, this can usually be avoided by careful monitoring by your doctor.

How should I take the medication?

  • You should swallow all of the medication at the same time each day.
  • To help you remember to take your medication, you might find it useful to mark a calendar or diary every day, or take your medication one hour before one of your meals.
  • If you forget to take your medication on one day, just take the normal dose the next day (but don't take two doses the next day). If you forget too may times, the medication might not be effective in killing all of the TB germs. You should tell your doctor or nurse if you keep forgetting to take your medication.
  • You should not drink alcohol while taking your medications. Check with your doctor before taking any new medications (including over the counter or complementary medications i.e. paracetamol), as some affect the medications taken to prevent TB.

Do I need to tell anyone about my treatment for TB infection?

People with TB infection alone cannot pass TB to anyone else, so there is no need to tell anyone at work, school or university if you don't want to. You should tell any other doctors that you see and they will keep this information confidential.

Other things to consider

Apart from the things mentioned above:

  • You should tell your doctor if you have other health problems or if you want to get pregnant.
  • You can continue all of your normal activities while taking this medication.

For more information

During the time that you are taking medication you will be seen regularly by a doctor or nurse to check your progress, but if you want more information contact your local chest clinic or see your doctor.​

Page Updated: Wednesday 25 June 2014
Contact page owner: Communicable Diseases