How Often Do You Get Your Period?

If you're a girl who's just started menstruating, you may have been surprised to find that after your first period, or menarche, you had to wait longer than a month for the next one. Or maybe your second period took you by surprise by coming much earlier than you expected. After all, periods are supposed to be predictable, aren't they? Is something wrong if they aren't?

Tampon and Calendar
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"Normal" Menstrual Cycles

While there are women who get their periods every 28 days like clockwork, there's a wide range of what's normal. And it's not at all unusual for a teen's periods to be irregular for the first few years of menstruation. You can skip several months between periods, or have two that are really close together. Or you may have spotting every few weeks, with very small amounts of menstrual blood. 

The menstrual cycle for adult women can last anywhere from 21 days to 35 days. The cycle for adolescent girls can be a bit longer—21 days to 45 days.

Why Periods Happen in the First Place

If your periods are irregular, it may help put your mind at ease to first understand how the menstrual cycle works and why you even bleed in the first place. Every month your body goes through two main phases to complete the cycle and begin a new one. The length of the menstrual cycle is measured from the first day of bleeding through the last day before your next period starts.

Day 1 of the menstrual cycle is the first day you see any amount of bleeding. This also signifies the first day of the follicular phase, when your hormones trigger an egg to start maturing in preparation for being released. When a mature egg leaves a Fallopian tube, it's called ovulation.

In the luteal phase, the uterine lining is made fully ready to nourish a fertilized egg if it implants--—in other words, if you become pregnant. If that doesn't happen, the lining deteriorates and is shed. That's the blood, tissue, and mucus you see when you have your period.

The reason a teen girl's periods may not be following a predictable pattern is simply that the hormone axis between the brain and ovaries that controls ovulation is still developing. After a year or two, when this hormone axis matures, periods should become more regular.

Keeping track of a menstrual cycle calendar or app can help you learn about your pattern and know whether you have "missed" a period or there is something affecting your menstrual cycle. It's also a handy way to make sure you've got pads, tampons, or your menstrual cup on hand before your period starts.

Other Reasons for Irregular Periods

Once you have a regular cycle and then notice you've missed a period, it could mean you're pregnant (if you've been having sex, of course). If you think that might be the case, you should take an at-home pregnancy test.

If your periods begin coming more than 35 days apart, or if you start having them really close together, there are lots of things that could be going on. You could be stressed, exercising too much, have lost a lot of weight, or you may have some sort of hormone imbalance. These are all problems that could cause you to stop ovulating, and, as a result, stop menstruating. Be sure to discuss any such changes over time with your pediatrician or gynecologist.

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  1. Adams Hillard PJ. Menstruation in adolescents: what do we know? And what do we do with the information? J Pediatr Adolesc Gynecol. 2014;27(6):309-19. doi:10.1016/j.jpag.2013.12.001

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