Azithromycin is an antibiotic used to treat traveller’s diarrhoea caused by bacterial infection. Take it exactly as prescribed and complete the course, even if symptoms improve. Drink plenty of fluids to avoid dehydration. Common side effects include nausea, stomach pain, diarrhoea, and headache. Seek medical advice if you develop severe diarrhoea, blood in stools, fever, or symptoms that do not improve.