Chemotherapy and antibiotics: safe use during cancer treatment

Do not use leftover antibiotics, share them or delay an urgent infection assessment while waiting to see whether tablets help. Chemotherapy can lower infection-fighting blood cells, and a person may need blood tests, cultures or hospital treatment rather than an unplanned prescription.

Antibiotics work against susceptible bacteria; they do not treat viral infections. The infection site, allergy history, kidney and liver function, recent medicines and local resistance patterns all influence selection. Samples may be taken before treatment when doing so will not delay urgent care.

Some antibiotics can change how other medicines are absorbed, processed or cleared. They may also add to effects such as diarrhoea, nausea, kidney strain, heart-rhythm changes or low blood counts. This does not mean the combination is always avoided; it means the prescribing teams need a complete medicine list and a monitoring plan.

Tell the prescriber that you are receiving chemotherapy and provide the regimen, last treatment date, allergies and all medicines or supplements. Let your oncology team know about the infection and prescription, even if another clinic issued it. Follow the label's dose and spacing instructions, and ask a pharmacist whether food, antacids or supplements affect absorption.

Complete the course unless the treating clinician changes it. If you miss a dose, follow the medicine leaflet or contact a pharmacist rather than doubling the next dose. Do not save unused medicine for a later fever or cough.

Diarrhoea during antibiotics can come from the medicine, infection or chemotherapy. Record its frequency and appearance, maintain fluids if you can, and contact the oncology team promptly when it is persistent, severe or accompanied by abdominal pain, fever, blood or weakness. Avoid anti-diarrhoea medicine until the team says it is suitable.

Use the oncology emergency number immediately for a temperature at or above your team's threshold, chills, shaking, sudden weakness, confusion, breathing difficulty, reduced urine, or feeling acutely unwell. Do this even while taking an antibiotic, because the infection may need different treatment or intravenous support.

Call emergency services for facial or throat swelling, wheezing, collapse, severe breathing trouble, or a widespread blistering or peeling rash after a dose. Stop and seek prompt prescriber advice for a new rash or troublesome reaction; do not restart a suspected medicine unless a clinician directs you.

Confirm why the antibiotic is needed, what organism or infection is suspected, how it fits around chemotherapy, and whether blood tests or dose changes are required. Ask which side effects need an immediate call, what to do after a missed dose and whether any current medicines, probiotics, antacids or supplements should be paused.