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What are antibiotics?

Antibiotics are medicines used to treat infections caused by bacteria. They work by either killing bacteria or preventing their growth. Different types of antibiotics are used to treat different types of infection.

When should antibiotics be used?

  • Antibiotics are only effective against infections caused by bacteria.
  • They do not work against infections caused by viruses such as common colds, flu, most coughs or sore throats.
  • Your doctor will only prescribe antibiotics when you need them. Antibiotics may be lifesaving for infections such as meningitis.
  • When you first come to hospital, often it’s too early to be sure of what is causing your illness, so doctors may give you antibiotics “just in case”.
  • If you are having an operation you may be given antibiotics to prevent an infection. This is known as prophylaxis and they will be given before surgery.

How long should I take antibiotics?

Antibiotics are given for a specific period of time and you should be told this information.

When doctors prescribe antibiotics “just in case”, they will “review” your response to treatment carefully.

  • If you are reviewed and your doctors decide that the illness isn’t caused by bacteria, they will stop antibiotics.
  • When your doctors have your test results they can decide how long you need antibiotics for and which ones you need.
  • Your doctors may also decide that you need to carry on with the antibiotics you had before, because they are right for your illness.

Regular review of antibiotic prescriptions helps to make sure that you only take the antibiotics you really need to make you better.

Do not give your antibiotics to friends, family or pets and do not keep left-over antibiotics. If you have received more doses than needed, hand these into your local pharmacy for safe disposal.

Remember: Take antibiotics responsibly!

What should I do when the antibiotics stop?

Tell your doctor if:

  • your fever goes up;
  • your symptoms come back

They can always restart your treatment if needed.

Special care

Please inform your doctor if you are pregnant or think you may be pregnant, are breast-feeding or have any liver or kidney problems.

If you have had Clostridium difficile (C. diff.) diarrhoea in the past, let your doctor know before taking any antibiotics.

After treatment with certain antibiotics, you may get a fungal infection such as thrush. This is because antibiotics can destroy your body’s “good”, as well as the “bad” bacteria responsible for the infection being treated.

If you develop an allergic reaction, signs of which include breathlessness, swelling and rash, stop taking the antibiotic and seek urgent medical attention.

Allergies, reactions

Some people can be allergic to antibiotics, particularly penicillin and similar medicines such as cephalosporins, and may experience swelling of the face and tongue and difficulty breathing when they take these antibiotics. This is called an anaphylactic reaction and it can be serious or even fatal.

Please give clear details of any previous reactions before being prescribed antibiotics. It is important that the most suitable type of antibiotic is given to you for the infection whilst also avoiding any harmful effects.

Remember: Remind your doctor, nurse or pharmacist of any allergies (including details of allergies, reactions) before you receive any antibiotics.

Taking other medication

Antibiotics may interfere with other medicines so it is important to tell your doctor and pharmacist about all the medicines you take, those prescribed and those bought by yourself, including herbal remedies.

If you are taking warfarin, you should have a blood test for the warfarin (INR check) three to five days after starting the antibiotic. You should inform the person taking the blood test that you are taking an antibiotic.

How to take antibiotics

Antibiotics are usually taken by mouth, but can sometimes be given into a vein (intravenous), into a muscle (intra-muscular) or applied to the affected part of the body such as skin, eyes or ears (also known as topical).

It is important to space the doses of antibiotic evenly throughout the day. It is not necessary to wake up to take them during the night. For example, if you need to take one capsule three times a day, take one at 8am, 3pm and 10pm.

Remember: Always follow the instructions on the label or refer to the medicine patient information leaflet.

Remember: Antibiotics won’t work against colds or flu!

What are the risks of taking antibiotics?

Taking antibiotics kills natural ‘good’ bacteria in your body, which help keep you healthy. Taking antibiotics causes the bacteria that your body carries to become “resistant” to antibiotics, meaning that common antibiotics don’t work anymore.

The more antibiotics you take the more likely you are:

  • to carry antibiotic resistant bacteria in your body – which can be passed on to other people such as your family, friends and pets;
  • to have antibiotic resistant infections in the future. When this happens, antibiotics will work less well or not at all.

Possible side-effects

Refer to the medicine patient information leaflet for all possible side-effects. The most common side-effects with antibiotics are diarrhoea, feeling sick and vomiting.

If diarrhoea is severe or watery, report this to your GP immediately.

For further information:

  • Ask your doctor, practice nurse or Pharmacist, or
  • Contact BHT Medicines Information on 01296 838220, or
  • Visit NHS

Find out about Antibiotic resistance on the NHS website (