All About Menstruation

Medically Reviewed by Renee A. Alli, MD on May 16, 2023
6 min read

Ever wonder what really happens during menstruation, when girls enter puberty and have their period? Maybe you’ve wanted to talk to your mom, sister, or dad about it. But each time you said the word "menstruation," you stuttered, stammered, and could barely pronounce it.

It’s OK. Everyone is timid when talking about bodily functions, especially one as mysterious as the menstrual period. Perhaps this article can answer some of your questions about this normal time in every girl's life.

Shortly after the beginning of puberty in girls, and usually about 2 years after the development of breasts, menstruation starts. While menstruation usually begins between ages 12 and 13, it may happen at a younger or older age. The first menstrual period is called "menarche."

The menstrual cycle is about four weeks long, starting on the first day of bleeding and ending when the next period begins. However, it can vary greatly when girls first starts their period. It may skip months or come several times per month for up to 2 years. It may be cramp-free early on. 

The menstrual discharge comes from the uterus through the vagina. The uterus is a hollow, pear-shaped organ, responsible for maintaining and nourishing the embryo and fetus during a pregnancy. The vagina, or "birth canal," provides a path for menstrual fluids to leave the body.

During a period, there are usually 2-3 days of relatively heavy bleeding followed by 2-4 days of lighter flow. The fluid during a menstrual cycle is a mixture of uterine lining tissue and blood.

The total monthly menstrual loss varies from about 4 to 12 teaspoons.

A few days before and during your period, you might feel cramping and bloating in your abdomen. The cramps are caused by increased production of hormones. These hormones (called prostaglandins) cause the muscles of the uterus to contract.

Many teens who have cramps also notice aching in the upper thighs along with lower back pain. Some also notice nausea, diarrhea, irritability, headaches, and fatigue, among other symptoms.

To ease cramping, try applying heat to your abdomen with a heating pad or hot water bottle. Taking a warm bath may also help. Some teens find that exercise helps relieve cramps. Exercise improves blood flow and produces endorphins, the body’s natural painkillers.

Simple but effective non-prescription pain relieving medications can ease symptoms. These include acetaminophen (Tylenol) and non-steroidal anti-inflammatory drugs (NSAIDs). NSAIDs include medications like ibuprofen (such as Motrin and Advil) and naproxen (such as Aleve). These drugs block the effects of prostaglandin hormones.

Discuss symptoms with your primary health care practitioner, so you can find the best medications and dosage.

Talk to your primary health care provider or your gynecologist if:

  • Your cramps are severe
  • Your bleeding is excessive, lasts longer than 7 days, occurs often or at the wrong time of your cycle
  • If you have not had your first period by age 16
  • If it has been 3 months since your last period
  • You think you might be pregnant
  • You develop fever and feel sick after tampon use

Cramps are normally worst during the first two to three days of your period, then ease as prostaglandin levels in the body return to normal. If cramps stay about the same throughout your period, or if over-the-counter painkillers don't really work, see a doctor.

Always ask your primary health care provider any questions you have about your period, making sure you clearly and completely describe any concerns.

Your first period may last from two to seven days. Then, there might be 21 to 40 days or even longer before you have another period. Your next period might be heavier or lighter than the first.

Don't worry if your early periods have longer cycles or don't follow a schedule. This irregularity is normal for at least the first 2 years.

Your periods should become more regular within two years after you start menstruating. Some teens have a 28-day cycle; some have a 24-day cycle; others have a 30- to 34-day cycle. All of these are normal. For young teens, cycles can range from 21 to 45 days. For adults, it can be 21-35 days. If your period is much shorter or longer, or if your period does not become regular after two years, see your primary health care provider.

It is possible to skip a month, especially if you have been ill, under stress, or exercising excessively. (Tell your health care provider at once, however, if you miss a period and are having sexual intercourse. Even if you are using effective birth control, pregnancy is a possibility!) But skipping for more than one month once your periods have become regular is another reason for a doctor visit.

When your period becomes regular, mark the date on your calendar for several months ahead. This will remind you to have tampons or pads on hand and help prevent accidents.

Ovulation is the release of a mature egg from a woman's ovary. It usually happens around mid cycle (about 14 days from the start of your last period).

Some might feel abdominal discomfort at the time of ovulation, but it’s usually very brief. This discomfort, medically called by its German name mittelschmerz (pain in the middle), can usually be relieved by the same medication used for cramps.

Premenstrual syndrome, or PMS, happens to many teens right before their periods start. With PMS, you might feel:

  • Mild breast tenderness
  • Fluid retention
  • Anxiety
  • Dietary cravings
  • Irritability
  • Difficulty sleeping or excessive sleeping

When menstruation begins, PMS symptoms decrease.

Some young women find that they cry easily and are more emotional during this time. Understanding the feelings that come with PMS may help you cope with the emotions. If your symptoms are serious and interfere with your life, discuss them with your health care practitioner.

Teens can use tampons, pads, or both during their period. Tampons are worn inside the vagina and come in a variety of sizes (small to large) with different absorbencies (light to super heavy). It’s important to change a tampon at least every four to 8 hours to avoid leakage and serious bacterial infections. According to the company Tampax, you can wear a tampon overnight, but insert a new one before bed and change it first thing in the morning.

Pads are usually self-adhesive and worn inside the underwear. You can find pads for light days, heavy days, and overnight. Change pads at least every four hours to avoid leakage and odor.

It’s important to understand your body as you decide on tampons or pads. Girls who participate in sports may find tampons less bulky and restrictive than pads. Girls are able to swim with tampons. Still, other girls think tampons are uncomfortable and prefer to use pads. It may take a while to find the right product for you.

Whether you choose tampons or pads, keep extras in your school locker or in a side pocket of your purse. Change the tampon or pad more frequently on heavy days to avoid an embarrassing stain on your clothes.

If you ever have trouble taking a tampon out, see your health care practitioner immediately. Tampons should be changed at least every 4 to 8 hours. Use the lowest absorbency tampon you can depending on your flow. Tampon use increases risk for toxic shock syndrome compared to pad use, especially if you don't change tampons frequently enough or use highest absorbency tampons on the lightest flow days. Toxic shock syndrome is a life-threatening disease related to toxins from bacteria.

Many things, such as the stress of exams or an illness like the flu, can cause you to skip a period. Too much exercise and low body weight may also cause the loss of your menstrual period. If you continue to miss your period, be sure to talk to your doctor.

If you are age 16 and still have not started your period, talk to your doctor to make sure there are no problems.