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What is an “irregular” menstrual cycle?

While some cycle variation is common, it’s good to know when to speak to a healthcare provider.

by Anna Druet, and Eve Lepage, MSN, RN Medically reviewed by Lynae Brayboy, MD, FACOG
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Top things to know about irregular cycles:

  • An irregular cycle is the term healthcare providers use to describe a menstrual cycle that continually falls outside of established clinical ranges for length and predictability. 

  • It is more common to experience unpredictable cycles at certain reproductive life stages.

  • You should speak to a healthcare provider if you experience sudden changes in your menstrual cycle.

A note from Clue’s Science team: Healthcare providers use terms like “abnormal” and “irregular” to describe variations from “normal” that extend beyond certain established clinical parameters (1). Since the word “normal” can make people feel “abnormal,” and the meaning of “normal” varies over time and across different cultures, we choose to use other words like “typical” and “unpredictable” instead. Just know that your healthcare provider may use more clinical terms like the ones mentioned above.

What is an “irregular cycle”?

An irregular cycle is the term healthcare providers use to describe a menstrual cycle that continually falls outside of “regular” ranges for unexpected reasons (1). People with irregular cycles may notice that their periods happen infrequently, frequently, or are very unpredictable. 

Your menstrual cycle is an indicator of your body’s overall functioning. It can let you know when everything is working as usual, when your body is going through a change, or when something’s not as it should be. Having an unpredictable period isn’t always a sign of a problem, and may have no pathological cause. The only way to know for sure is to see your healthcare provider to make sure there’s no underlying reason. 

Are your periods irregular? Use Clue to keep track.

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What causes unpredictable periods?

Some variability in your cycle length is typical (2). Unpredictable cycles can occur at any age, but there are certain stages in the reproductive lifespan when it is common for menstrual cycles to be somewhat unpredictable. These include:

  • The first few years after menarche(when your periods first begin in life). The average age of menarche in developed countries is 12-13 years old. For the first few years of menstruation, most girls and adolescents will have menstrual cycles between 21–45 days in length, but longer or shorter cycles may be typical. By the third year, the majority will experience menstrual cycles 24–38 days range, as is typical in adults (3).

  • Pregnancy (you can take a pregnancy test to rule this out) 

  • After pregnancy (postpartum) (4)

  • Breastfeeding/chestfeeding (5)

  • Perimenopause (the few years before your menstrual cycles come to an end, typically after age 45). After entering perimenopause, cycle length can vary between 14 and 50 days, though some women and people with cycles may report very little change in their menstrual cycles before menopause (6).

Other common causes include:

Why this matters

Your menstrual cycle can give your healthcare provider a glimpse into the status of your body’s functioning. An sudden unpredictable menstrual cycle (not caused by hormonal birth control) may be the first sign of a treatable health condition. This is why it's important to have any potential issues diagnosed as early as possible, and managed with the help of a healthcare provider.

When to see a healthcare provider

You should speak to your healthcare provider if:

  • Your periods suddenly become unpredictable and you’re under the age of 45 (1)

  • You have menstrual cycles shorter than 24 days or longer than 38 days (1)

  • Your periods last longer than eight days (1)

  • You’re between the ages of 18–45 and your menstrual cycles vary by more than seven to nine days (for example, a cycle that is 27 days long one month, 42 the next) (1)

  • Your periods suddenly stop for more than 90 days (exceptions include pregnancy, chest/breastfeeding, menopause, and recently discontinued hormonal birth control) (14,15)

  • You have unpredictable cycles and you’re planning to become pregnant (16)

When talking to your healthcare provider, be sure to tell them about your cycle history including cycle length, period length, and volume of bleeding. If you’re using the Clue app, you can find information about your cycle variation in the Analysis tab. Also, tell them if you’ve recently noticed unexpected changes in your body, such as unexplained abdominal pain, unexplained weight changes, or unusual hair growth on your face or body. 

A healthcare provider will probably ask questions about your medical and menstrual history and perform a simple physical exam. In some cases, they may also:

  • Ask you questions about your full health history, including medical and surgical history, social history, family medical history, and when your mother went into menopause. 

  • Perform blood tests.

  • Perform a pelvic exam and or/an ultrasound (sonogram) to inspect the inside of the uterus and the ovaries. 

  • Take a sample of your uterine lining (endometrial biopsy) (17).

Rarely, an unpredictable cycle can be a sign of an atypical hypothalamic-pituitary-ovarian (HPO) axis. Your healthcare provider may perform an MRI or brain scan to rule this out. You can learn more about the HPO axis in this article (18).

Your menstrual cycle can be considered a vital sign to your overall health. This is why tracking your cycle is so important – it can help you identify when something’s changed, and when to seek the advice of a healthcare provider. You can use the Clue app to track things like the dates of your periods, the volume of bleeding, and other cycle-related experiences like mood, energy, and sleep. 

An earlier version of this article was published on November 19, 2018

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