Progesterone needs to be taken orally for 3-5 consecutive days and withdrawal bleeding, i.e. normal menstrual flow, can occur 3-7 days after discontinuation, up to a maximum of 10 days. The occurrence of withdrawal bleeding after a few days of progesterone administration is determined by the specific thickness of the lining. Progesterone to produce withdrawal bleeding prerequisite for the body has a certain amount of estrogen, in the role of estrogen, progesterone is given to cause withdrawal bleeding. Progesterone is usually taken for 3-5 days and then discontinued, and menstruation can occur within 3-7 days under normal circumstances. If the body estrogen is too little or take progesterone amount is not enough, produce retreat bleeding time also varies, the longest can reach 10 days. Progesterone should not be taken casually, but strictly according to medical advice, as it has certain side effects, such as dizziness, nausea, depression, breast tenderness, and can even lead to weight gain or abnormal liver function in women.