The period refers to menstruation, 51 years old does not come to menstruation, may be a normal phenomenon, may also be abnormal, according to the specific situation analysis. 1. Normal phenomenon: most 51-year-old women are already in menopause, when the function of the ovaries will decline, causing changes in hormone levels in the body menstrual disorders, and some have even appeared menopause, this situation is normal. In addition, there are some women who are 51 years old when the ovaries still have ovulation function, if they have sex and do not take contraceptive measures, there may be pregnancy caused by not menstruation. 2. Abnormal: Some other factors, such as mental tension, stress, environmental changes, etc. can cause abnormal hormone levels in the body to delay menstruation, which is not normal. In addition, overwork, dieting, weight loss, etc. can also cause women’s endocrine disorders, which is also abnormal. If you are 51 years old and don’t have menstruation, you can go to the hospital for differential diagnosis, and if it is caused by diseases, you should actively treat it.