A normal menstrual cycle is typically between 21 and 35 days and can last up to 7 days. There are many potential causes for abnormal or irregular bleeding, including problems with ovulation, fibroids and polyps, bleeding disorders, pre-cancer and cancer of the lining of the uterus and some medications. In evaluating irregular periods, a thorough history and exam can help guide what other tests or exams may be needed to help diagnose the cause of abnormal bleeding. Sometimes irregular bleeding can be treated with medications while in other circumstances may be treated with surgical procedures.