Side effects to look for before you buy Oseltamivir online include but are not limited to nausea, vomiting, diarrhea, headaches, and dizziness. Taking oseltamivir along with food generally helps with nausea. Other reports include skin reactions, seizures and a change in diabetic levels. These side effects will occur as your body adjusts to the medication and will subside after a few days. As with any medication, if the symptoms continue, contact your local physician. Allergic reactions can occur and will result in symptoms of itching, swelling, trouble breathing, and rash.