A period that lasts longer than seven days is considered abnormal menstruation, and the Cleveland Clinic explains that stress, disease, birth control pills and other serious conditions could be causing a long period. Women with periods lasting over a week should seek medical assistance.
Diseases such as polycystic ovarian syndrome, endometriosis, uterine fibroids, pelvic inflammatory disease, uterine cancer or cervical cancer can bring on abnormal menstruation. Endometriosis and uterine fibroids can cause painful prolonged periods that make the menstrual cycle unbearable. Many of these diseases are accompanied by other symptoms such as vomiting, nausea, abdominal discomfort, cramping, painful intercourse, diarrhea, heavy vaginal discharge and weight gain, the Cleveland Clinic adds.
Factors such as stress can affect the length of a period as well. A woman who has recently gained or lost weight or has experience changes in her eating, exercise, travel and work routines may experience prolonged periods. Going on or off birth control can impact a woman's period for up to six months after making the change, according to the Cleveland Clinic. Birth control pills contain hormones that can cause irregular bleeding and spotting between periods. Bleeding between periods becomes a serious issue if the woman is soaking through a pad or tampon every two to three hours.