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:
- chest infections
- ear infections in children
- sore throats
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:
- are unlikely to clear up without antibiotics
- could infect others
- could take too long to clear without treatment
- carry a risk of more serious complications
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:
- tablets, capsules or a liquid that you drink – these can be used to treat most types of mild to moderate infections in the body
- creams, lotions, sprays and drops – these are often used to treat skin infections and eye or ear infections
- injections – these can be given as an injection or through a drip directly into the blood or muscle, and are used for more serious infections
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:
- being sick
- feeling sick
- bloating and indigestion
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 get a skin rash that may include itchy, red, swollen, blistered or peeling skin
- you're wheezing
- you get tightness in the chest or throat
- you have trouble breathing or talking
- your mouth, face, lips, tongue or throat start swelling
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.
- Penicillins (such as penicillin, amoxicillin, co-amoxiclav, flucloxacillin and phenoxymethylpenicillin) – widely used to treat a variety of infections, including skin infections, chest infections and urinary tract infections
- Cephalosporins (such as cefalexin) – used to treat a wide range of infections, but some are also effective for treating more serious infections, such as sepsis and meningitis
- Aminoglycosides (such as gentamicin and tobramycin) – tend to only be used in hospital to treat very serious illnesses such as sepsis, as they can cause serious side effects, including hearing loss and kidney damage; they're usually given by injection, but may be given as drops for some ear or eye infections
- Tetracyclines (such as tetracycline, doxycycline and lymecycline) – can be used to treat a wide range of infections, but are commonly used to treat acne and a skin condition called rosacea
- Macrolides (such as azithromycin, erythromycin and clarithromycin) – can be particularly useful for treating lung and chest infections, or as an alternative for people with a penicillin allergy, or to treat penicillin-resistant strains of bacteria
- Fluoroquinolones (such as ciprofloxacin and levofloxacin) – are broad-spectrum antibiotics that were once used to treat a wide range of infections, especially respiratory and urinary tract infections; these antibiotics are no longer used routinely because of the risk of serious side effects
Page last reviewed: 11 November 2022
Next review due: 11 November 2025