A menstrual cycle longer than 35 days is considered scanty, so a menstrual cycle of 40 to 50 days is not normal. Normal menstruation is cyclical and self-limiting. The first day of bleeding is the beginning of the menstrual cycle, and the interval between the first day of two menstrual periods is called a menstrual cycle. It usually lasts from 21 to 35 days, with an average of 28 days, and more than 35 days is abnormal. Environmental changes, overwork, mental stimulation or stress can cause endocrine dysfunction, which in turn causes menstrual cramps. Common diseases causing scanty menstruation include polycystic ovary syndrome, early onset ovarian insufficiency, hypothyroidism, hyperprolactinemia, etc., which may be accompanied by obesity, unresponsiveness, decreased libido and infertility. It is recommended to consult a doctor in time, through the examination of sex hormone six, gynecological ultrasound can find out the cause of prolonged menstrual cycle, and the doctor will give targeted menstrual regulation treatment.