Urinary antibiotics (grouped by use)
Trimethoprim
Urine infectionsSome chest infections
Start a diary for this antibiotic
Usually prescribed for:Urine infection (cystitis)
Information follows NICE antimicrobial prescribing guidance and the BNF.
Common side effects
- Feeling sick
- Being sick
- Diarrhoea
- Headache
- Itchy skin rash
How often each one happens varies by medicine and product, so check your leaflet. Many are mild, but ask your pharmacist or doctor if they are troublesome or do not settle.
Less common side effects
- Raised potassium levels
Get medical help straight away if you notice
- Blistering or peeling rash, or mouth or eye sores: stop the medicine and call 999 or go to A&E
- Unexplained bruising, bleeding, or a sore throat with fever
Taking it safely
- Not usually recommended in the first 12 weeks of pregnancy. Tell your prescriber if you are pregnant or trying to conceive, as extra folic acid may be needed.
- Tell your prescriber if you take methotrexate or medicines for blood pressure.
Report a side effect
You can report any suspected side effect to the UK Yellow Card scheme at yellowcard.mhra.gov.uk.