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What is the Most Common Menstrual Cycle Length?

Tricia Christensen
Updated Feb 20, 2024
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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.

WiseGEEK is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
Tricia Christensen
By Tricia Christensen , Writer
With a Literature degree from Sonoma State University and years of experience as a WiseGEEK contributor, Tricia Christensen is based in Northern California and brings a wealth of knowledge and passion to her writing. Her wide-ranging interests include reading, writing, medicine, art, film, history, politics, ethics, and religion, all of which she incorporates into her informative articles. Tricia is currently working on her first novel.

Discussion Comments

By browncoat — On Nov 06, 2014

@clintflint - It probably does depend on the person though, because I don't think I've ever had a period that didn't happen like clockwork exactly when I was expecting it and whether I wanted it to arrive or not.

And I've had no lack of stressful occasions in my life. The only time it has been interfered with at all was when I was on the pill and it stopped for a while after I got off it again, but the doctor told me that was pretty normal.

By clintflint — On Nov 06, 2014

@Ana1234 - It isn't always health that affects the menstruation cycle. Stress can definitely effect it as well, both making it longer and shorter. I actually believe that women can almost control, to a point, when they have their period. I know there have been times when I have desperately not wanted it to arrive on a particular date, because I tend to get very bad cramps when it does, and it has been delayed.

And I had a friend in high school who had been abused and she told me that her period lasted for three weeks at a time because she felt more protected when it was happening.

Now stress is the common factor here and it might just be that stress effects everyone differently causing irregular menstrual cycles, rather than ever being manipulated by conscious choice.

By Ana1234 — On Nov 05, 2014

I have been tracking my menstrual cycle for several years now and it's actually a really good source of information when you are going to the doctor. Being able to actually point out dates to back up what you're saying about your menstrual cycle length seems to get more action than just telling them it has been longer or shorter than usual.

I have a hormonal condition that effects my period and so the differences can directly indicate how my health is in general.

Tricia Christensen

Tricia Christensen


With a Literature degree from Sonoma State University and years of experience as a WiseGEEK contributor, Tricia...
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