How long does a normal menstrual cycle last?

Menstruation helps your body get ready for the possibility of pregnancy each month. Each month, an ovary releases an egg. The egg travels through a tube called the fallopian tube into the uterus. Hormones make the lining of the uterus thicker to get ready for a baby in case the egg is fertilized by sperm. If a man’s sperm does not fertilize the egg, the uterus sheds the lining it prepared for a baby. When the uterus sheds its lining, blood flows out of your vagina. This is called menstrual flow, or your period.

A menstrual cycle is the time from the day your period starts to the time your next period starts. Your menstrual cycle may vary from 21 to 35 days long. Most periods last 3 to 5 days, but anywhere from 2 to 7 days is normal. Menstrual cycles may start around the same date every month or they may be irregular.

When is a period late or missed?

A late period means that it hasn’t started 5 or more days after the day you expected it to start. A missed period means that you have had no menstrual flow for 6 or more weeks after the start of your last period.

What is the cause?

During the first couple of years of menstruation many teens have irregular periods. During this time your body is still developing and your ovaries may not release an egg every month. As a result, your cycles may be irregular. You may have a period every 2 weeks or once every 3 months. Most girls’ menstrual cycles become regular as their hormone levels mature. A few women will continue to have irregular periods, which may be normal for them. Other causes of a late or missed period are:

• Pregnancy. Pregnancy is the most common cause of missed periods in teens. If you are pregnant, you will not have a normal period until after the baby is born.

  If your period is late and you have had sex even once in the past several months, see your healthcare provider for a pregnancy test. Most home test kits are accurate, but may give incorrect or unclear results. It is important to find out early if you are pregnant. Starting prenatal care right away helps you have a healthy baby.

• Stress. Stress is the second most common cause of late or missed periods in teenagers. It may be emotional stress, for example, breakup with a boyfriend or final exams. Or it may be physical stress, such as a severe illness, a sexually transmitted disease, rapid weight loss or gain, or strenuous exercise. Dieting or binging and purging may interrupt menstrual cycles. Changes in your usual routine (for example, going on vacation) may also cause your period to be late or missed.
• Hormone imbalance. In some cases a hormone imbalance causes missed periods. For example, if you have been taking birth control pills, your periods may be irregular for a while when you stop taking the pills. If you are having sex after you stop taking birth control pills, be sure to use another reliable method of birth control if you don’t want to get pregnant.

Problems of the thyroid gland, pituitary gland, adrenal glands, or ovaries are other rare causes of irregular periods.

How is it diagnosed?

Your healthcare provider will ask about your symptoms and medical history and examine you, including a pelvic exam. Tests may include:

• A pregnancy test
• Blood tests

You may have other tests or scans to check for other possible causes of your symptoms.

How is it treated?

The treatment depends on the cause. Examples of possible treatments are:

• Exercising less if you have a very strenuous exercise program
• Learning to manage stress if stress may be a cause
• Taking birth control pills or other hormone medicine to help your body have the right balance of hormones
• Having surgery

In some cases, you may not need treatment.

How can I take care of myself?

Follow the full course of treatment prescribed by your healthcare provider. In addition:

• Mark on a calendar the dates when each period starts and stops. This information can help your healthcare provider make a correct diagnosis. Take the calendar to your appointment.
• Eat healthy foods and keep your weight steady.
  • If you are overweight, a healthy diet and regular exercise will help you lose weight slowly. It’s best to lose no more than 2 pounds a week.
  • If you are underweight, a dietician can help you plan a healthy diet to gain weight.
  • Talk with your healthcare provider if you are not sure what your proper weight should be, or if others are worried about your weight.
• If you have sex and want to prevent pregnancy, always use birth control. Talk to your healthcare provider about your choices.
• If you have had sex, get a pregnancy test if your period is 5 or more days late.
• Take care of your health. Try to get at least 7 to 9 hours of sleep each night. If you smoke, try to quit. If you want to drink alcohol, ask your healthcare provider how much is safe for you to drink. Learn ways to manage stress. Exercise according to your healthcare provider’s instructions. If you exercise hard every day, you may need to cut back until your periods come back.

Ask your provider:

• How and when you will hear your test results
• If there are activities you should avoid and when you can return to your normal activities
• How to take care of yourself at home
• What symptoms or problems you should watch for and what to do if you have them

Make sure you know when you should come back for a checkup. Keep all appointments for provider visits or tests.