Teenage Menstruation: When they usually start and what are the signs

Image: iStock


Teenage is the phase in which girls experience menarche or their first menstruation. The median age for menarche is 12 to 13 years in most populations. The menstrual cycle in most girls ranges from 21 to 45 days during the initial years. The duration of the period can be shorter or longer, depending on individual factors.

Read this post to understand the facts of teenage periods and how to deal with them.

When Do Most Girls Get Their Period?

Menarche or the first menstruation usually happens around the age of 12 years for most girls. However, there is no fixed age for menarche. It is considered normal for a girl to have menarche between the ages of ten and 15 years (1). Hormonal changes can vary in each girl, so the age of menarche can be different (2). 98% of girls have menarche by the age of 15.

The following signs may indicate that the girl may begin her menstruation soon.

  • Menarche may occur about two years after the beginning of the breast development
  • Vaginal discharge may begin six months or a year before the first period

If the first period is delayed more than usual or occurs before ten years of age, known as precocious puberty, it requires medical attention.

What Causes A Period?

Hormonal changes in a girl’s body are responsible for menstruation or period. Ovaries in females release the hormones progesterone and estrogen. These hormones thicken the uterus’ inner lining (endometrium) in preparation for the attachment of a fertilized egg (ovum). If the fertilization does not occur during the ovulation period, these hormone levels gradually decrease.

The decreased levels of estrogen and progesterone cause shedding of the endometrial lining, and menstruation begins. Blood and tissues lining the endometrium are expelled through the vagina as menses. The usual length of menstruation can be four to six days. Each month the same mechanism repeats through the reproductive years of a woman’s life (3).

How Does Ovulation Relate To Periods?

Ovulation is the release of the egg (ovum) from the ovaries, while menstruation is the shedding of the endometrial lining along with blood. The hormones that cause thickness of the uterine lining in preparation for the fertilized egg are also responsible for ovulation (4).

After ovulation, the ovum travels through the fallopian tube to reach the uterus. If the fertilization happens, the fertilized ovum moves down to the uterus and attaches to its thick wall. Hormones prevent the shedding of the uterus lining, and the baby can grow in the womb.

If the ovum is not fertilized, the decreased levels of hormones cause the uterus’ lining to shed, leading to menstruation. Thus, ovulation and menstruation or periods are related events.

What Are The Signs That A Girl Is About To Start A Period?

Some girls may experience emotional and physical changes before menstruation. This condition is known as premenstrual syndrome (PMS) and causes the following signs and symptoms (5).

  • Sadness
  • Anxiety
  • Mood swings
  • Bloating
  • Acne
  • Nausea
  • Back pain
  • Food cravings
  • Fatigue

Some may even have these signs and symptoms during menstruation. Usually, these symptoms resolve within the first few days of the period. Some girls may not have any signs and symptoms before or during menstruation.

Do Periods Happen Regularly At The Start Of Menstruation?

It is normal to have irregular menstruation during the first few years after menarche, although not all girls may experience it. Hormonal changes could affect changes in the menstrual cycle. About 60-80% of girls will have 21-34 days long cycle similar to adult women within three years after menarche (1).

Usually, the menstrual cycle should be regular and repeated every four to five weeks. If the menstruation occurs with irregular patterns, you may consult a gynecologist to exclude any cause of concern. Early identification may help to manage hormonal imbalance with diet and lifestyle modifications in most girls.

Which Menstrual Product Is Best To Absorb Blood?

There are various choices to deal with menstruation. Pads, tampons, or menstrual cups are used to absorb or collect the blood and vaginal secretions during periods. Some girls may choose one menstrual product, whereas some may try various methods.

Trying various products could help a girl identify the most convenient option. It is essential to know the right method of use. The following are some salient points related to various menstrual products and their use.

  • Pads are often the preferred choice during the initial years of menstruation. Cotton pads of different sizes are available in the market. The girl may choose one after multiple trials. Highly absorbent pads are the most preferred type. Changing pads on time is essential to avoid skin irritation and maintain personal hygiene.
  • Tampons are cotton plugs that can be placed into the vagina. Most tampons come with an applicator to help in insertion. Some girls may find tampons more efficient than pads. It may also make a girl feel comfortable while performing physical activities, such as swimming. You should not leave the tampon for more than eight hours since this may increase the risk of infection.
  • Menstrual cups are inserted into the vagina, and it holds blood until emptied. These silicone cups need to be sterilized and reused up to their expiry date. You may choose a cup size based on the girl’s preference and the flow of menses.

Choosing the right menstrual product and learning its correct use can make periods easier to manage for girls.

When To Worry About Menstrual Problems?

Most girls usually have normal periods. The following situations may require you to consult a gynecologist.

  • No menstruation after 15 years of age
  • Irregular periods for more than two years after menarche
  • Bleeding between periods
  • Severe cramps even after taking OTC medications
  • Heavy bleeding
  • Period lasting more than a week
  • Severe PMS interfering with daily activities

Although most girls will have normal menstruation in later years, it is ideal to consult a gynecologist to begin early interventions for any underlying problems.

Is It Possible To Be Pregnant As Soon As The Period Starts?

A girl can get pregnant as soon as the period begins. Even right before the menarche (first period), it is possible to become pregnant since each month before periods, including the first period, the hormones cause ovulation.

The uterine wall is also ready for the attachment of fertilized eggs and to develop the fetus. Therefore, the ovum (egg) could be fertilized if the girl has unprotected sex. Early sex education may help to prevent preteen and teen pregnancies in many cases.

Frequently Asked Questions

1. What to do for menstrual cramps?

Many girls can have menstrual cramps during the first few years. The following methods may help to deal with it.

  • Keep a heated pad on the lower belly
  • Take ibuprofen or naproxen

Mild, merely annoying menstrual cramps can be managed in these ways. However, severe cramps interfering with daily activities can be due to conditions such as uterine fibroids or endometriosis. You may seek medical care for severe cramps.

2. How much blood is lost during menstruation?

Although it may look like a lot of bleeding during menstruation, typically, it can be around 10 to 35 ml of blood loss per period in most girls. Heavy periods (menorrhagia) can cause a loss of more than 80 ml of blood in each period (6). It requires medical care since blood loss can increase the risk of iron deficiency and anemia.

Menstruation is a physiological process in a healthy girl’s life. It should not change the way a girl lives her life. Girls should not be stopped from playing, exercising, or performing any other activities during menstruation. Parents should ensure their girls have a positive perception of menstruation and manage it appropriately with menstrual products.


MomJunction's health articles are written after analyzing various scientific reports and assertions from expert authors and institutions. Our references (citations) consist of resources established by authorities in their respective fields. You can learn more about the authenticity of the information we present in our editorial policy.
1. Menstruation in Girls and Adolescents: Using the Menstrual Cycle as a Vital Sign; The American College of Obstetricians and Gynecologists
2. Your First Period; The American College of Obstetricians and Gynecologists
3. Menstruation; MedlinePlus; US National Library of Medicine
4. Periods and fertility in the menstrual cycle; National Health Service
5. Premenstrual Syndrome (PMS); Harvard Medical School
6. Very Heavy Menstrual Flow; The Center for Menstrual Cycle and Ovulation Research

Recommended Articles: