Doctors consider normal menstrual bleeding a period that lasts from three to seven days; prolonged menstrual bleeding, or menorrhagia, is defined as bleeding that goes beyond a week.

The length of an average menstrual cycle for an adult woman lasts anywhere between 21 and 35 days. Younger girls just entering puberty and older women approaching menopause might notice that their periods follow irregular patterns, either lasting shorter or longer than normal or perhaps with a flow that becomes heavier or lighter.

Medical conditions that could be the cause of abnormal menstrual bleeding include:
- Dysfunctional uterune bleeding
- Uterine fibroids, non-cancerous growths of the uterus wall
- Endometrial hyperplasia, a thickened endometrium
- A bleeding disorder, like von Willebrand disease
- Problems with clotting
- Thyroid functioning
- Glandular issues
- Infection
- Ovarian cysts
- Uterine polyps
- Cancer
- Interuterine device
- Hormonal imbalance

Prolonged menstrual bleeding may just be part of a bothersome pattern for some women or a sign of a medical condition that should be addressed.  If something doesn't feel right to you, always ask your doctor, and keep a detailed account of your menstrual bleeding in order to provide your doctor with another piece of the diagnostic puzzle.