The most common cause of menstruation is bleeding during ovulation, if one of the two periods is less heavy and usually lasts for 3-5 days, or if the bleeding is spotting. This type of bleeding does not require treatment. If you want to treat it, you can take estrogen or short-acting oral contraceptives to adjust your menstrual cycle. If the two periods are about the same amount and last longer, there may be an endocrine disorder. The most common reason is that there is no normal ovulation, or the follicles are not mature, and the corpus luteum atrophies prematurely, causing vaginal bleeding. In this case, it is necessary to check the sex hormone six and thyroid hormone, to check whether it is caused by endocrine reasons. Check progesterone one week after ovulation, if the progesterone level is relatively low, that is, the follicle is not well developed, the progesterone level can not reach, there is a breakthrough bleeding of estrogen. Therefore, if there are two menstrual periods half a month apart, you must go to the hospital for examination to determine the cause and treat accordingly.