Delayed menstruation for 20 days can be seen in many cases. If you have a regular menstrual cycle and have been sexually active, you should first rule out the possibility of early pregnancy if your period is delayed for 20 days, and you can rule out the possibility of pregnancy by taking a urine test for early pregnancy or taking a blood test for HCG, or human chorionic gonadotropin. There is also the case of irregular menstrual cycles, the cycle itself is not fixed, 40-60 days or even longer cycle, then the delayed menstruation can not be determined whether the abnormality. This is because the menstrual cycle is greatly influenced by mood, environment, and emotions, and the menstrual cycle may be delayed accordingly under the influence of these factors. Therefore, for those who have irregular menstrual cycles or are not sexually active, further menstrual regulation treatment should be done after ruling out organic pathologies.