What to Know About Irregular Periods in Teenagers

It is quite common for some girls to have irregular periods during their first year of menstruation. However, it's not normal if she misses her period for three to five months in a row, especially if she has had a period regularly for some months before that.

The medical term for not having periods is amenorrhea, and when this condition goes beyond three months, then a trip to see your doctor is usually needed.

Parents of teen daughters with irregular periods often ask these questions: Why is my teen daughter's period only once every two months? Or why does she get her period twice a month? Why does it last for only two days one month and 10 days the next?

There are many reasons that your daughter may be experiencing irregular periods, listed below are some things both you and your daughter should discuss.

Irregular Cycles

It is normal for a girl during her first two years of menstruating to have an irregular menstrual cycle. Some women have irregular periods for their entire lives, although most women have a cycle that they can count out.

The 28-day cycle that is written about in books and followed by doctors is an average, not the rule. A teen's body is influenced by its growth and therefore can start and stop the menstrual cycle while it's growing.

Fluctuating Hormones

The length of time in days and the amount of blood of a girl's period is influenced by the amount of hormones that her body is currently manufacturing. Therefore, it is normal for a teen who is growing and has fluctuating hormones for the amount of blood and the length of time her period lasts to be different from one period to the next.

Other Factors

There are many outside influences that can cause irregular periods, including these:

  • Medications
  • Significant weight gain or loss
  • Over-exercise
  • Poor nutrition (or a diet too high in carbohydrates)
  • Drug use
  • Eating disorders
  • Increased stress

If you feel one of these influences may be causing your teen's irregular periods, you should talk to her doctor.

Predicting Your Period

Teach your daughter to start recognizing the signs and symptoms of her period so she will have an idea of when it is coming. If she has irregular periods, you'll want her to carry a pad with her at all times, as it will be best if she is prepared when she does get her period.

You should ask her to mark down on a calendar when her period starts and when it ends. This is important because if her irregular periods become a medical problem you will have the answers to her doctor's questions about when she had her periods and how irregular they were.

Missing Several Periods

While skipping one month or having a shorter or longer span of days between periods isn't abnormal for a teen, if your daughter's period doesn't show for a much longer amount of time, you'll want to consult her doctor.


If your teen is sexually active and skips a period, she should be seen by a doctor to rule out pregnancy. If she is normally irregular she should still see a doctor after two 28-day cycles of not getting her period. A missed period is still a sign of pregnancy even in women who have irregular periods.

The development of amenorrhea—absence of a menstrual period for three months or more—should be reported to your teen's doctor as it could be a sign of premature ovarian failure, a condition that fully develops in a woman's 40s.

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  1. The Nemours Foundation. My Periods Are Irregular. What's Going On? Updated November 2015.

  2. National Institute of Child Health and Human Development. What causes menstrual irregularities? Updated January 31, 2017.

  3. Rebar RW. Premature Ovarian "Failure" in the Adolescent. Ann N Y Acad Sci. 2008;1135:138-145. doi:10.1196/annals.1429.000