For years people were told all antibiotics interfere with the contraceptive pill, but current evidence shows most do not. The main exceptions are certain enzyme-inducing antibiotics, such as rifampicin and rifabutin, which can reduce hormonal contraception.
Illness itself can be a bigger issue: if an infection causes vomiting or significant diarrhoea, the pill may not be absorbed properly, which can lower its effectiveness regardless of the antibiotic.
If you are taking rifampicin or are unwell with vomiting or diarrhoea, use additional precautions such as condoms and ask your pharmacist or clinician for tailored advice on your specific antibiotic and contraceptive method.