Is irregular uterine bleeding that occurs in the absence of recognizable pelvic pathology, general medical disease, or pregnancy. It reflects a disruption in the normal cyclic pattern of ovulatory hormonal stimulation to the endometrial lining. The bleeding is unpredictable in many ways. It may be excessively heavy or light and may be prolonged, frequent, or random.
Vaginal bleeding that occurs more often than every 21 days or farther apart than 35 days (a normal teen menstrual cycle can last up to 45 days).
Vaginal bleeding that lasts longer than 7 days (normally lasts 4 to 6 days).
Blood loss of more than 80 mL each menstrual cycle [normally about 30 mL ]. If you are passing blood clots and soaking through your usual pads or tampons each hour for 2 or more hours, your bleeding is considered severe.