“Normal” menstrual cycles vary from person to person. Lots of different things can change your cycle, but a missed period may mean it’s time to take a pregnancy test.

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What’s a “normal” menstrual cycle?

Your menstrual cycle lasts from the first day of your period to the first day of your next period. The average menstrual cycle is about 25-30 days, but it can be as short as 21 days or longer than 35 — it’s different from person to person. The number of days in your cycle may also vary from month to month. When you get your period, it’s normal to bleed anywhere from 2 to 7 days.

The average person loses anywhere between 1-6 tablespoons of menstrual fluid during each period. It can be thin or clumpy, and varies in color from dark red to brown or pink. (When you first start having your period, it may last only a few days or be super light.) If your period is so heavy that you have to change maxi pads or super tampons every hour, call your doctor or your local Planned Parenthood health center.

Everyone’s body is different, so their periods are different too — what’s “normal” varies from person to person, and can change over your lifetime. Some birth control methods or health conditions may also affect your period.

What if I miss a period?

A missed period is one of the first signs of pregnancy, but it doesn’t always mean you’re pregnant. Sometimes you skip a period for no reason at all, especially during the first few years of your period. Lots of other things can throw off your regular cycle and mess with the timing of your period. These include:

  • Using hormonal birth control, like the pill, patch, ring, implant, and hormonal IUD

  • Taking the morning after pill

  • Changes in your hormones

  • Being sick

  • Taking certain medicines

  • Exercising too much

  • Poor diet and nutrition

  • Stress

  • Sudden weight gain or loss

  • Having very little body fat, which can happen if you’re an athlete or have an eating disorder

  • Menopause (when your period stops for good)

Take a pregnancy test if you had unprotected sex and then missed your period. Just missing your period isn’t a foolproof way to know that you’re pregnant — a pregnancy test is the only way to find out for sure. You can get a pregnancy test at drugstores or your local Planned Parenthood health center.

Hormonal birth control can affect your cycle, and even make your period stop altogether. If you’ve been using your birth control correctly or are on a highly effective method (like the IUD or implant), it’s very, very unlikely that a missed period means you’re pregnant. But you can always take a pregnancy test to be sure.

What if my period is irregular?

It’s really common to have irregular menstrual cycles at some point in your life — especially when you first start getting your period.

Examples of irregular periods include:

  • Missing a period altogether

  • Your period coming early or late

  • Different PMS symptoms

  • Heavier or lighter bleeding than usual

  • Bleeding longer than usual

  • Unpredictable timing of periods from month to month

Keeping track of your periods and symptoms on a menstrual cycle calendar or in an app is good way to learn what’s normal for your body, and help you know if anything changes.

Some people’s periods are irregular a lot. It may just be the way their body naturally works, or it can be caused by a health problem. If many of your periods are irregular, unpredictable, or abnormal, talk with a doctor to make sure everything’s okay. They can also help you find a hormonal birth control method that may help make your period lighter and/or more regular.

When should I see a doctor about my menstrual cycle?

Contact your doctor or your local Planned Parenthood health center if:

  • You’re worried that you might be pregnant because you’ve had unprotected sex and missed your period.

  • Your period is so heavy that you have to change maxi pads or super tampons every hour.

  • Your period lasts much longer than usual, or longer than 7 days.  

  • You're light-headed, dizzy, or your pulse is racing.

  • You’re 16 years old and still haven’t gotten your period.

  • You have severe pain before or during your period.

  • You have unusual bleeding between periods.

  • You suddenly feel sick or get a fever when using a tampon.

  • Your periods or PMS keeps you from your normal day-to-day activities.

  • Your periods stop or suddenly become irregular.

  • Your period comes more often than every 21 days or less often than every 45 days.

  • You get very anxious or depressed around the time you get your period.

Where can I go for help if I’m having problems with my period?

You can talk with your family doctor or gynecologist if you're having a painful menstrual cycle or are worried about period symptoms or PMS. You can also visit a community health clinic or your local Planned Parenthood health center.