It is not normal for menstruation to come a week early. If the menstrual cycle is less than 25 days, it is abnormal, so it is recommended to actively go to the hospital for examination. Shortened menstrual cycle is commonly caused by the following reasons: First, due to endocrine disorders, progesterone deficiency, early atrophy of the corpus luteum, so it can cause shortened menstrual cycle, it is recommended to actively give clinical treatment. Secondly, submucosal fibroids or large interstitial fibroids may cause early menstruation and increased menstrual flow. Third, it may be caused by blood diseases, such as thrombocytopenia, which may also lead to early menstruation. Fourth, endometrial inflammation, endometrial polyps and so on may cause early menstruation, so find out the cause before giving treatment.