Azithromycin is an antibiotic medication used to treat a variety of bacterial infections, including respiratory infections, skin infections, and sexually transmitted infections. It works by stopping the growth of bacteria. Common side effects include nausea, vomiting, and diarrhea. It is important to take this medication exactly as prescribed by your doctor and to finish the entire course of treatment, even if you start feeling better. Contact your doctor if you experience severe or persistent side effects, or if your symptoms do not improve after a few days of treatment.