Menstruation
Menstruation is the most visible phase of the menstrual cycle and its beginning is used as the marker between cycles. The first day of menstrual bleeding is the date used for the last menstrual period (LMP). The typical length of time between the first day of one period and the first day of the next is 21 to 45 days in young women, and 21 to 31 days in adults (an average of 28 days).
Abnormal uterine bleeding
Symptoms include vaginal bleeding that occurs irregular, at abnormal frequency, last excessively long, or is more than normal. Normal frequency of periods is 22 to 38 days. Variation in the length of time between cycles is typically less than 21 days. Bleeding typically last less than 9 days and blood loss is less than 80 mL. Excessive blood loss may also be defined as that which negatively affects a person's quality of life. Bleeding more than six month after menopause is also a concern.