After you start a course of antibiotics, the length of time that you stay infectious can vary.
Why does it vary?
Whether you’re still infectious can depend on several factors, such as:
- The type of infection that you have. Different types of infection are infectious for different periods of time. Some infections can be contagious before any symptoms show.
- How mild or severe your infection is. A severe infection may take longer to become non-infectious than one that is mild. Some severe infections may also need more than one course of antibiotics.
- How long it takes the antibiotics to start working. This can vary too. For example, it may be affected by how well your body absorbs the antibiotics, and how much of the medicine reaches the infection within your body.
- The length of your course of antibiotics. This will depend on what infection you have, how severe it is, and how well you respond to treatment. Most courses of antibiotics last 5-7 days. However, some urinary tract infections (UTIs) can be treated with one dose, while an infection like tuberculosis (TB) may require treatment for a long time.
- Whether you’re taking other medicines, as well as your antibiotics. Other medicines may interact with your antibiotics. Your GP will take this into account when prescribing your medicine.
Advice from your GP
If you’re concerned about how long you’ll be infectious, it’s best to seek advice from your GP. They can give you information about, for example:
- the infection that you have, and
- how long you may be infectious after starting your course of antibiotics.
Antibiotics don’t work on viruses
Your GP will prescribe antibiotics to treat an infection caused by bacteria. Antibiotics are not prescribed for infections caused by viruses, because antibiotics do not work on viruses.
How do antibiotics work?
Antibiotics work by killing bacteria, or by stopping the bacteria from multiplying, which allows your body’s immune system to get rid of them.
Finish your course of antibiotics
It’s important to finish your course of antibiotics, even if your symptoms have gone and you’re feeling better. The length of your course is intended to get rid of all the bacteria causing the infection.
If you don’t finish the course, some bacteria may remain, and the infection may come back. Or the bacteria may develop resistance to that type of antibiotic. This could mean that the antibiotics may not work if you need to take them again in the future.
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