It depends. Some changes in menstruation are normal and should not cause concern. It is possible for a woman to miss her period because of weight loss or gain, vigorous exercise, stress, illness, or other changes that affect her body.
In older women, menstrual periods usually become lighter and less frequent as menopause approaches and hormone levels decrease, although sometimes periods become heavier and more frequent.
Since pregnancy can also cause missed periods, if there is any possibility of pregnancy, a woman should make an appointment with her clinician.
If a woman has bleeding or spotting between periods, or bleeding after intercourse, or heavier or more painful periods and is sexually active, she should schedule an appointment to be checked for STIs (sexually transmitted infections).