Sixteen days of menstruation again may be ovulatory bleeding, irregular menstruation or gynecological diseases, other factors and other causes. 1. Ovulation bleeding, such as the usual regular menstrual cycle in about 30 days, menstruation sixteen days and came back, is likely to be ovulation bleeding. The small amount of bleeding caused by the drop of hormone level in the body after ovulation leads to the shedding of part of the uterine lining, and it is not normal menstrual blood. It is not normal menstrual blood. It can be observed temporarily and does not require treatment. 2. Irregular menstruation, menstruation sixteen days again, such as bleeding volume, time and normal menstrual period similar, may be endocrine disorders or organic lesions caused by irregular menstruation, such as polycystic ovary syndrome, uterine fibroids and other diseases, may affect the normal menstrual period, resulting in the phenomenon of frequent menstruation. Combination of ultrasound and sex hormone six tests are needed to treat the symptoms. 3. Gynecological diseases, menstruation sixteen days and come again, but also alert to whether the cervicitis, cervical polyps or cervical cancer and other diseases caused by irregular bleeding phenomenon, usually accompanied by abdominal pain, leukorrhea, odor or contact bleeding and other symptoms, and is not menstrual bleeding. Cervical polyps are recommended to be removed surgically; cervical cancer can be treated with surgery or radiotherapy. 4. Other factors, menstruation sixteen days again may also be the recent use of emergency contraceptive pills, to check the cause of bleeding and location of symptomatic treatment. It is recommended that if you have abnormal vaginal bleeding, consult a doctor for a clear diagnosis and symptomatic treatment.