If you have not had your period for 12 days, and you are not sexually active, you may want to consider recent causes of menstrual disorders, such as stress at work, change of living environment, weight loss, etc. Remove the cause first. If you can have normal menstruation after removing the cause, just observe. If the cause is removed and menstruation occurs normally, observation is sufficient. If menstruation does not occur normally, it is necessary to go to the hospital for a clear diagnosis before using medication. If the woman is already sexually active, it is necessary to clarify whether she is pregnant or not. If she is pregnant, consider pregnancy test according to the specific situation. If you are not pregnant, you need to clarify why your menstrual cycle is irregular and what kind of self-causes you have, just like women who are not sexually active, and then remove the causes of the disease before using medication. If you choose to use medication, it is recommended that oral progesterone, such as progesterone or dextroprogesterone, be used for 10 days, depending on the specific dosage, to achieve a good endothelial conversion that leads to menstruation. If only one irregular menstruation can be observed, if it is repeated for more than 3 times of abnormal menstrual cycles, it is recommended to go to the hospital for further clarification of the diagnosis and treatment.