Period Guide

Know Your Flow: Can Your Menstrual Cycle Length Vary Month to Month?

Due to a variety of factors, the length of your menstrual cycle can vary from month to month. Variations can be normal and totally healthy, however sometimes these can be a sign of something more serious.

What’s a regular cycle length?

The average menstrual cycle is 28 days. Cycles in adults can range from 21 to 35 days. For teens, the range is wider. When you start your period, long cycles are common, but menstrual cycles tend to shorten and become more regular as you age. The length of the period can also vary. While most periods last from 3 to 5 days, anywhere from 2 to 7 days is considered normal. Someone with a regular period will tend to have the same cycle length month to month.

What’s the role of hormones in your cycle?

Your menstrual cycle (and its length) is controlled by the rise and fall of levels of hormones during the month. During the first half of your cycle, rising hormone levels help prepare (see also: thicken) the uterine lining for pregnancy. If the egg is not fertilized (aka you don’t get pregnant), then hormone levels begin to drop, and the thickened lining of the uterus is shed during your period. Therefore, if something affects your hormones this can impact your period and the length of your menstrual cycle, sometimes causing you to miss “x” number of cycles altogether.

What can impact hormone levels & change your cycle length?

Many things can impact your hormone levels and thus affect the length of your menstrual cycle. Here are some examples:

  • Stress can mess with your cycle. Like super stress. In such dire situations, your body and brain go into survival mode. This can include shutting off the ovulation hormones to avoid reproduction during a potentially dangerous time.
  • Excessive exercise similarly puts stress on your system, which can impact your hormone levels. Also, your body needs a certain amount of body fat to ovulate, so excessive exercise and/or weight loss can put this balance into jeopardy.
  • Extreme weight gain can cause the body to produce extra testosterone, which can prevent ovulation.
  • Smoking can cause you to experience more severe PMS, more painful periods and have irregular cycles.  This is because, according to research, smoking may alter levels of estrogen, progesterone and other hormones associated with your cycle.
  • Alcohol can also impact your hormone levels, causing an imbalance which can affect your cycle.
  • Medical conditions like PCOS, Thyroid Disease, and others can also cause your period length to change from month to month.

How do you determine your cycle length?

A menstrual cycle is counted from the first day of one period to the first day of the next period. An easy way to figure this out is by tracking your period!

When should you be concerned?

While your cycle length can vary, consistently irregular periods should be addressed with your doctor.

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