Generally women will begin having Menstrual periods between the ages of 10 to 16. The age of Menopause can vary from 35 to 60. Between these years the average cycle will occur anywhere from 21 to every 35 days and last for 3 to 7 days. Many things can affect the regularity of the Menstrual cycle. Genetics, stress, body fat, weight changes, medical problems, medications, and pregnancy are some of the most common reason for irregular cycles. Some women can be irregular their whole life while others experience only rare variation of their cycles. If you are experiencing irregular cycles or you have noticed a sudden change in your cycles then you should schedule an appointment to come in to talk with a Physician or Nurse Practitioner to help you determine if there is any cause for concern.