Antibiotics can be essential for bacterial infections, but they do not treat colds or flu caused by viruses. When treatment is needed, knowing which symptoms can wait for advice and which need urgent care helps you use the medicine safely.[1]
Mild effects still deserve attention
Nausea and diarrhoea are familiar antibiotic side effects. Dizziness and yeast infections, including thrush, can also occur. The possibilities vary by medicine, so read your own leaflet. Contact a pharmacist or prescriber about symptoms that trouble you rather than assuming every antibiotic has the same risks.[1][2]
An upset stomach alone does not establish an allergy. Report a new rash to a clinician, including the antibiotic’s name and when symptoms started. Those details help them assess the reaction.[2]
Recognise an emergency
Call your local emergency number for trouble breathing or speaking, a tight throat, swelling of the lips or tongue, or collapse. A blistering or peeling rash can also signal a serious reaction and needs emergency assessment. Do not wait for the next routine appointment.[2]
Diarrhoea can continue after treatment
Antibiotics can upset the balance of gut bacteria, allowing Clostridioides difficile, or C. diff, to cause infection. Not every episode of diarrhoea is C. diff, and symptoms alone cannot reliably identify the cause. Contact a healthcare professional about diarrhoea during or after antibiotic treatment.[3]
Seek prompt assessment when diarrhoea is severe or persistent, especially with fever, stomach pain or dehydration. Tell the clinician about recent antibiotics even if the course has finished. Older people, those with weakened immunity and people with previous C. diff face greater risk.[3]
Check warnings specific to your antibiotic
Fluoroquinolones have particular tendon and nerve warnings. If new tendon, muscle or joint pain, tingling or numbness develops, official advice is to stop that fluoroquinolone and contact a clinician immediately. This specific instruction does not mean every antibiotic should be stopped for mild nausea.[2]
Food and alcohol instructions differ. Metronidazole and tinidazole require alcohol avoidance during treatment and for a specified period afterwards. Rifampicin and rifabutin can reduce the combined contraceptive pill’s effectiveness; ask about additional protection.[4]
Keep the treatment plan clear
Follow the prescribed instructions. Do not share antibiotics or keep leftovers for a later illness. Ask your prescriber how to handle side effects or missed doses, and mention pregnancy, breastfeeding and other medicines when suitability is checked.[1][5]
This adult guide is general information. Your medicine’s leaflet and professional advice should guide your treatment.
Editorial disclosure: General health education, not a personal diagnosis or treatment plan. References checked on 20 October 2026; no clinician-review claim is made. The retained featured image is an illustrative AI-generated image.
References
- CDC: Antibiotic use
- NHS: Antibiotic side effects
- CDC: C. diff
- NHS: Antibiotic interactions
- NHS: Antibiotics
