How Often Do You Get Your Period?

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Question: How Often Do Girls Have Periods?

Answer: A menstrual cycle is the complete "monthly" cycle, which begins and ends with the first day of bleeding. An entire cycle typically lasts 28 days, so a new cycle starts about every 4 weeks.

Your menstrual cycle is the basis of your reproductive health and your health in general. If your menstrual cycle is abnormal as a teen it could be a warning sign of health problems as an adult.

Every month your body goes through two main phases to complete the cycle and begin a new one. These are the Follicular Phase and the Luteal Phase. The length of the menstrual cycle is measured from the first day of bleeding or the first day of your period through the last day before your next period starts. Day 1 of the menstrual cycle is the first day you experience any amount of bleeding. The last day before your next period would be Day 28 if you have the average 28-day menstrual cycle. Normal menstrual cycle length, in adolescent girls, is 21 to 45 days. Normal menstrual cycle length in adult women is from 21 to 35 days.

See also: Your Menstrual Cycle Calendar

During the first few years of menstruation, periods are often irregular. You may skip several months between your first period, or menarche, and the next time you menstruate. It is also probable that you may have two periods that are 28 days apart and then skip a period.

Or you may have spotting every few weeks. Usually, if your first year of cycles is irregular it is because the hormone axis between your brain and ovaries that controls ovulation is still developing.


Menstruation in girls and adolescents: using the menstrual cycle as a vital sign. Committee Opinion No.

651. American College of Obstetricians and Gynecologists. Obstet Gynecol 2015;126:e143–6.

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