Normal menstrual flow lasts approximately 5 days and occurs every 21 to 35 days. Abnormal uterine bleeding is when you bleed between your monthly periods, or when you bleed for too long or it is an extremely heavy flow.

What causes abnormal uterine bleeding?

There are many causes of abnormal uterine bleeding. One major cause is due to structural abnormalities in the uterus. This can take the form of fibroids, which are benign overgrowth of the muscle of the uterus. This can also take the form of polyps, which are benign overgrowths of the lining of the uterus or on the cervix. Uterine cancer or cervical cancer is an important cause as well.

There are also non-structural causes of abnormal uterine bleeding. Bleeding disorders or platelet dysfunction can cause abnormal bleeding. Early pregnancies can have some bleeding associated with them. Hormonal changes can also be a cause.

Polycystic ovary syndrome (PCOS, cysts in the ovaries) may cause your periods to come at different times or not at all. It is caused when certain hormones are out of balance. When this happens, you may have difficulty getting pregnant. You may grow hair on your body and face. Also, the hair on your scalp may get thinner.

Women who are going into menopause or are in menopause are more apt to have changes in hormones. The changes can cause the lining of the uterus (endometrium) to get thick. This can cause bleeding.

For women who are in menopause, any bleeding should be thought of as not normal and should be investigated.

Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy