The most common reason for delayed menstruation at the age of 43 is the decline in ovarian function and hormone levels. Due to individual differences, the manifestation of ovarian function decline in menstruation is also different, some people will have frequent menstruation and increased menstrual flow, while others will have delayed menstruation, decreased menstrual flow, or the time of menstruation has been shortened or lengthened. So each person’s constitution is different, and the clinical symptoms that appear after entering menopause are also different, which is a common cause. Of course, there are other reasons that may cause delayed menstruation, such as hyperprolactinemia or hyperandrogenemia, which may lead to delayed menstruation, so it is best to take a blood test for sex hormone 6 to find out whether the cause of delayed menstruation is related to the endocrine system.