Amenorrhea is the medical term used when a female is not having a period, when she should be.  Amenorrhea can be classed as either primary or secondary. The features of primary amenorrhea involve the absence of a period in a 15 to 16 year old girl who has otherwise gone through normal developmental changes.  Secondary amenorrhea is diagnosed when a woman who has had regular menstrual cycles stops having her period.  In many cases, the cause of secondary amenorrhea can be changes in your routine, excessive weight loss, eating disorders, excessive exercising, stress, and pregnancy.  Other causes for secondary amenorrhea can include medications taken for other medical conditions, such as schizophrenia or chemotherapy agents used to treat cancer. Medical conditions that can cause secondary amenorrhea include polycystic ovarian syndrome, thyroid function abnormalities, and tumors found near the pituitary gland in the brain. Your doctor will do lab work and run tests to look for any underlying medical causes for your amenorrhea. In some cases, your doctor may prescribe progesterone supplements to correct the problem. Progesterone helps cause a withdrawal bleed similar to your period. You do not necessarily have a progesterone deficiency if you have amenorrhea. Short-term use of either oral medication, progesterone injections, or vaginal gel, may be prescribed to help balance your hormones and cause you to resume your regular periods. If you continue to have problems with abnormal cycles, your doctor may prescribe oral contraceptives that contain progesterone to help establish a regular cycle. He or she will monitor your progress to determine the best time to discontinue the medications. Get emergency medical help if you have any signs of an allergic reaction. Signs of an allergic reaction include hives, difficulty breathing, and swelling in your face, mouth, or throat.

TL;DR in Vietnamese:
Trị mất kinh. Cùng bác sĩ tìm ra nguyên nhân mất kinh. Sử dụng thuốc bổ sung progesterone theo chỉ định. Tìm biện pháp chăm sóc y tế ngay nếu xuất hiện phản ứng dị ứng.