What is the Most Common Menstrual Cycle Length?

Menstrual cycle length means the whole cycle, including ovulation and menstruation. Sometimes people get this issue confused and think of the menstrual cycle as only the days when menstrual bleeding or the period occurs. Actually, these days are simply the beginning, and the cycle ends the day before the next menstrual bleeding begins. For many women menstrual cycle length is 28 days, but there is much normal variation.

Some women have relatively short cycles, lasting less than the four weeks, and other women may have much longer cycles than can exceed a month in length. These are not abnormal and they represent the exceptional range in physical normality exhibited by the human female. There are clearly times when cycle length isn’t what would be viewed as normal. Less than a three week cycle may be abnormal and more than 40 days between periods could also be viewed with some concern.

These differences don’t necessarily indicate poor health, but they might suggest problems with reproductive health. This is particularly true for a very short menstrual cycle length that corresponds to a short luteal phase (the time between ovulation and first period day). Short luteal phase is less than 10 days between ovulation and menstruation. It may be difficult for pregnancy to occur because the body does not build up sufficient lining for a fetus to safely implant. Clearly, when a cycle is very short, the luteal phase may be under 10 days, and this is a good thing to discuss with a doctor, if a pregnancy is part of a woman’s plans.

Sometimes women will experience cessation of their menstrual cycle altogether. This is not uncommon among competitive athletes, but it also occurs in those who have eating disorders or who suffer from extreme malnutrition. As fat reserves in the body sink below a certain level, amenorrhea or period cessation could occur. This isn’t necessarily dangerous, but if poor nutrition or eating disorders are the cause, getting medical attention is wise. Once a higher body fat percentage is reached, women usually return to an average menstrual cycle length.

Perhaps more important than the days in a cycle is the regularity of it. A predictable cycle is useful, but not all women experience this either. Brief changes are common and a single late period is not irregularity. Frequently having no idea when a cycle will begin or end is a little more problematic and could have several causes.

Irregularity in menstrual cycle length might be due to any condition affecting regular production of estrogen or progesterone. As women age and begin to approach menopause, changes in menstrual cycle length are very common. Yet, since pregnancy is still possible, what appears to be a missed period should be investigated as potential pregnancy. Still, lots of women note fluctuations in length and could have a variety of short and long cycles for several years leading up to period cessation.

Hormones can become imbalanced at other times, and conditions like polycystic ovarian disease may lead to irregular menstrual cycle length. Other glandular disorders may affect hormone production. For instance people with thyroid disease or problems with the pituitary gland could have unpredictable menstrual cycle length.

Since occasionally cycle length that varies may suggest other health conditions, it can be a smart idea to track it for a few months. This information can be brought to a gynecologist or family doctor to discuss whether irregularities might be a cause for concern. What no woman should be deeply concerned about is a regular cycle that is a little shorter or longer than 28 days. This is extremely normal.