Antibiotics

Antibiotics are used to treat or prevent some types of bacterial infection. They work by killing bacteria or preventing them from spreading. But they do not work for everything.

Many mild bacterial infections get better on their own without using antibiotics.

Antibiotics do not work for viral infections such as colds and flu, and most coughs.

Antibiotics are no longer routinely used to treat:

When it comes to antibiotics, take your doctor's advice on whether you need them or not. Antibiotic resistance is a big problem – taking antibiotics when you do not need them can mean they will not work for you in the future.

When antibiotics are needed

Antibiotics may be used to treat bacterial infections that:

You may still be infectious after starting a course of antibiotics. Depending on the infection and how it's treated, it can take between 48 hours and 14 days to stop being infectious. Ask a GP or pharmacist for advice.

People at a high risk of infection may also be given antibiotics as a precaution, known as antibiotic prophylaxis.

Read more about when antibiotics are used and why antibiotics are not routinely used to treat infections.

How to take antibiotics

Take antibiotics as directed on the packet or the patient information leaflet that comes with the medicine, or as instructed by your GP or pharmacist.

Antibiotics can come as:

Missing a dose of antibiotics

If you forget to take a dose of your antibiotics, check the patient information leaflet that came with your medicine to find out what to do. If you're not sure, speak to a pharmacist or a GP.

In most cases, you can take the dose you missed as soon as you remember and then continue to take your course of antibiotics as normal.

But if it's almost time for the next dose, skip the missed dose and continue your regular dosing schedule. Do not take a double dose to make up for a missed one.

Accidentally taking an extra dose

There's an increased risk of side effects if you take 2 doses closer together than recommended.

Accidentally taking 1 extra dose of your antibiotic is unlikely to cause you any serious harm.

But it will increase your chances of getting side effects, such as pain in your stomach, diarrhoea, and feeling or being sick.

If you accidentally take more than 1 extra dose of your antibiotic, are worried or you get severe side effects, speak to your GP or call NHS 111 as soon as possible.

Side effects of antibiotics

As with any medicine, antibiotics can cause side effects. Most antibiotics do not cause problems if they're used properly and serious side effects are rare.

The common side effects include:

Some people may have an allergic reaction to antibiotics, especially penicillin and another type of antibiotic called cephalosporins.

In very rare cases, this can lead to a serious allergic reaction (anaphylaxis), which is a medical emergency.

Call 999 or go to A&E now if:

You could be having a serious allergic reaction and may need immediate treatment in hospital.

Read more about the side effects of antibiotics.

Considerations and interactions

Some antibiotics are not suitable for people with certain medical problems, or women who are pregnant or breastfeeding.

Tell your healthcare professional if you're pregnant or breastfeeding so they can prescribe the most suitable antibiotic for you.

Only ever take antibiotics prescribed for you – never "borrow" them from a friend or family member.

Some antibiotics do not mix well with other medicines, such as the contraceptive pill and alcohol.

Read the information leaflet that comes with your medicine carefully and discuss any concerns with your pharmacist or GP.

Read more about how antibiotics interact with other medicines.

Types of antibiotics

There are hundreds of different types of antibiotics, but most of them can be classified into 6 groups.

Other antibiotics include chloramphenicol (used for eye and ear infections), fusidic acid (used for skin and eye infections), and nitrofurantoin and trimethoprim (used for urinary tract infections).

Page last reviewed: 11 November 2022
Next review due: 11 November 2025