What is the average menstruation cycle length?
Menstrual cycle
The first period usually begins between twelve and fifteen years of age, a point in time known as menarche.[5] They may occasionally start as early as eight, and this onset may still be normal.[6] The average age of the first period is generally later in the developing world and earlier in developed world. 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 35 days in adults (an average of 28 days[6][7][8]). Menstruation stops occurring after menopause which usually occurs between 45 and 55 years of age.[9] Bleeding usually lasts around 2 to 7 days.[6]
Menstrual disorder
Abnormal uterine bleeding is a general category that includes any bleeding from menstrual or nonmenstrual causes. Hypomenorrhea is abnormally light menstrual periods. Menorrhagia (meno = month, rrhagia = excessive flow/discharge) is an abnormally heavy and prolonged menstrual period. Metrorrhagia is bleeding at irregular times, especially outside the expected intervals of the menstrual cycle. If there is excessive menstrual and uterine bleeding other than that caused by menstruation, menometrorrhagia (meno = prolonged, metro = uterine, rrhagia = excessive flow/discharge) may be diagnosed. Causes may be due to abnormal blood clotting, disruption of normal hormonal regulation of periods or disorders of the endometrial lining of the uterus. Depending upon the cause, it may be associated with abnormally painful periods.