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Menstruation 101
All you need to know about your system, your cycle, FAQ’s and more.
Your First Period
The Baiscs

Menstruation is the monthly discharge of blood and mucosal tissue from the uterus through the vagina. Here are a few general points regarding the range of experience that women have with their periods:

Menarche is the time of your first menstrual period, normally occurs between the ages of 11 and 13. By the age of 15, 98% of girls will have had their first periods. This is the time during puberty that you start to transform from girl to a young woman. It is a truly unique occurrence marking the start of your journey to womanhood.

F.Y.I

  • A woman typically loses less than 16 teaspoons (< 60 mL) of blood each month during her period.
  • Most women have periods that are from 3 to 8 days in length. The average is 6 days.
  • A woman gets her period roughly every 4 weeks from the time she has her first period (menarche) until menstruation stops (menopause)
  • The lengths of a woman's menstrual cycles vary the most during the few years’ right after menarche (first period) and in the year’s right before menopause.

Getting to know the female reproductive system will help you understand your period better. Use this diagram to learn about different parts of your system.

This will better equip you to find out the important role each part plays in your menstrual cycle


vagina (vuh-JY-nuh)
the canal that leads from the cervix to the outside of the body and through which menstrual fluid passes; a baby also come into the world through the vagina

your reproductive system

ovaries (OH-vuhr-ees)
two reproductive glands that produce hormones and eggs

fallopian (fuh-LOH-pee-uhn) tubes
two tubes through which the egg travels from the ovary to the uterus

uterus (YOOT-er-uhs)
muscular organ in the body where a fertilized egg implants and grows into a baby

endometrium (en-doh-MEET-ree-um)
the lining of the uterus that is shed every month

cervix (SER-viks)
the lower part of the uterus which opens into upper part of vagina

Phases of Your Cycle
its more than just your period

The idea of getting your first period may be a little scary. When will it happen? Where will it happen? Will I know what to do? These are natural questions. Don’t worry; the best way to tackle anything is knowledge (knowing about it) and preparation. Every woman has worried about being caught off guard by her period. The best way to avoid this is to learn about your cycle. Plan ahead and use Butterfly’s Period Planner to keep track of your periods.

When you think about your menstrual cycle, do you think of just your period? For some of us, those few days of bleeding are the only thing we think about, since it’s easy to associate your cycle with the time of the month when you may experience some other physical symptoms like headaches, bloating, pain in the legs, backaches and abdominal cramps. But while your period is the part of your menstrual cycle that you actually see, there’s a lot more going on behind the scenes.

a recyrring cycle of activites inside the body

The menstrual cycle is made up of many changes that take place inside the body. These changes help prepare a woman's body for pregnancy each month. The progression of the cycle from one to the next is caused by rise and fall of hormone levels throughout a specific interval, usually about 28 days, or one month. But while the typical menstrual cycle lasts from 21 to 35 days, it can vary from woman to woman. Menstrual cycles can be irregular during puberty, and the year’s right before menopause.

How many days does your cycle last? Chart it with the Butterfly Period Planner.


Days 1 through 5

First day of your period is day one of your monthly cycle.
Hormones are released from pituitary gland in the brain, signaling several egg follicles the ovaries to grow.

Day 6 through 13

After menstruation ends, one dominant follicle continues to Grow. Besides the growing egg in it, a hormone called estrogen is produced. This causes the endometrium to increase in thickness. Estrogen’s job is to reform the broken lining of the uterus.

Days 14 - Ovulation

A surge of hormones causes dominant egg to be released from ovary.

Days 15 through 25

As the mature egg travels through fallopian tube towards the uterus, ‘Corpus Leuteum’ is created from the empty follicide. Corpus leuteum produce progestron which causes the lining of the uterus to become spongy and receptive.

Days 25 through 28

If implantation of a fertilized egg does not occur, the corpus leutuem disintegrates and estrogen and progestron levels fall causing endometrium to break down. The result is shedding of endometrium through menstruation, which begins day 1 of the cycle again.

F.Y.I

Once your period begins it can remain irregular for about 2 years or more. Once it is regular, keep track of the cycle on a calendar. Mark the first day, how heavy the flow is each day, how many days it lasts, and how many days are between the beginning of one period and the beginning of the next. The entire menstrual cycle is, on average, about 28 days long. But a difference of a few days more or less is considered to be normal.

Your period is the beginning of the menstrual cycle. Keep track for a few months. Pretty soon, you will know about when your period will start and you will know how to prepare for it. You’ll also get a better idea of what kind of flow (heavy or light) to expect each day of your period.

chart your monthly symptoms

Charting symptoms as they occur can help you get a clear picture of your menstrual cycle. When you document how you feel each day for a few consecutive months, you may begin to see trends in your monthly cycle, like if you experience symptoms, and whether you experience symptoms at the same time each month. This information can help your health care professional understand the severity and frequency of your symptoms and can help guide treatment options that might be right for you.



Please Note: This cycle calendar is not a formal diagnostic tool. It is meant to help you identify and track possible symptoms related to your menstrual cycle for discussion with your health care professional. Other medical conditions may cause similar symptoms. Please seek medical advice from your health care professional if you have any questions or concerns about your menstrual cycle or any symptoms that may be related to your menstrual cycle.

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