You can't wait too long before starting Tamiflu: "When you or someone in your family begins to experience flu symptoms, you have 48 hours to take action."
- For flu treatment: When taken within two days of experiencing symptoms, TAMIFLU works by helping to stop the flu virus from spreading inside the body
- For flu prevention: When you have been exposed to someone with the flu, taking TAMIFLU can help keep the virus from making you sick
http://www.tamiflu.com/treat.aspx