Quick answer
What is amoxicillin used for?
Amoxicillin is a penicillin antibiotic used for bacterial infections such as some chest, ear, sinus, dental and urine infections. Complete the course unless you have an allergic reaction. It does not treat viruses. Diarrhoea is common; a widespread rash or breathing difficulty needs urgent advice.
What amoxicillin treats
Amoxicillin is a penicillin antibiotic. It is used for bacterial infections such as some chest infections, ear infections, sinusitis, dental infections and urinary tract infections. It is also used with other medicines as part of H. pylori treatment for stomach ulcers.
It does not work against viruses, so it will not shorten a typical cold or flu. Prescribers follow guidance to avoid unnecessary antibiotics and reduce resistance.
How to take amoxicillin
Adults and children have different doses based on age, weight and the infection. Liquid medicine for children should be shaken well; use an oral syringe for accurate measuring.
Space doses evenly — often three times a day. Complete the course even if you feel better, unless you are told to stop because of a reaction.
Side effects
Common effects include diarrhoea, nausea and mild rash. Contact a GP or pharmacist if diarrhoea is severe or contains blood, or if you become very unwell.
A rash can mean allergy, but not every rash is anaphylaxis. Seek same-day advice for a new widespread rash. For breathing difficulty or facial swelling, call 999.
Allergy and interactions
People with a penicillin allergy must not take amoxicillin. Cross-reaction with some other antibiotics is possible — always list your allergies.
Amoxicillin can interact with medicines such as methotrexate and, rarely, affect warfarin monitoring. Tell the prescriber about all medicines you take. Combined hormonal contraception advice has changed over time — ask a pharmacist if you are unsure whether extra precautions are needed with your specific antibiotic course.
When to get help during treatment
If symptoms are much worse after 48 hours, you develop a high fever again, or you cannot keep medicine down, contact a GP or call 111. For children, follow NHS guidance on fever and dehydration, and seek urgent help if they are not drinking, are floppy, or are hard to wake.
Common questions about amoxicillin
- What if I have a penicillin allergy?
- If you have a true penicillin allergy, avoid amoxicillin and other penicillins. Tell every healthcare professional and check medicine labels. Many people labelled "allergic" in childhood were never truly allergic — a GP or allergy clinic can sometimes review this safely.
- Can I take amoxicillin with food or alcohol?
- Amoxicillin can be taken with or without food. There is no direct dangerous interaction with alcohol, but resting and staying hydrated while unwell is sensible, and alcohol can worsen side effects such as nausea.
- What should I do if I miss a dose?
- Take it as soon as you remember unless it is nearly time for the next dose. Do not take two doses together. Try to keep doses evenly spaced across the day.
- Why must I finish the course?
- Stopping early can allow bacteria to survive and symptoms to return. If side effects are severe, contact a GP or pharmacist rather than stopping without advice — they may change the antibiotic.
- Can amoxicillin cause thrush or diarrhoea?
- Yes. Antibiotics can disturb normal bacteria, leading to diarrhoea or vaginal/oral thrush. Mild diarrhoea is common; severe, bloody or persistent diarrhoea needs medical advice because of the rare risk of C. difficile infection.