Your first menstrual period is called menarche (say "MEN-ar-kee"). It usually starts sometime between ages 11 and 14.¹ But it can happen as early as age 9 or as late as 15. If you are a teenage girl, see your doctor if you have not started having periods by age 15. Menarche is a sign you are growing up and becoming a woman. Along with starting your period, your body is changing. You've begun to develop breasts, pubic hair, and underarm hair, and your hips have begun to widen. Menarche also means that if you have sex, you can get pregnant. You can even get pregnant in the month before your first period starts.

Starting your period

In the days before you start your period, you may feel tense or emotional. You may gain water weight and feel bloated. You may have pain (cramps) in your abdomen, back, or legs that lasts a few hours or more. Your breasts may be tender, and your face may break out.

When you start your period, you'll notice a spot of blood on your underwear or when you use the bathroom. The flow of blood from your vagina is usually light at first and may get heavier for a few days before tapering off. The blood may be a brownish color at first and then turn brighter red. Your period will usually last 3 to 7 days each month.

Ask your mom, a health professional, or a woman you trust for advice on using feminine products for the bleeding, such as tampons or pads. A tampon fits inside your vagina and is good to use when swimming or doing other physical activities. A pad has adhesive strips that help it stick to your underwear. You'll need to change tampons and pads regularly. Having a period won't prevent you from doing any of the activities you normally do, and no one will be able to tell when you're having one.

If you have cramps with your period, regular exercise, a heating pad, a warm bath, and nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen or naproxen may help. If you are younger than 20, do not take aspirin. Aspirin raises the risk of Reye's syndrome, a disease that affects the brain and liver. If these treatments don't help, talk to your doctor about prescription medicines.

Your menstrual cycle

Your period is part of your menstrual cycle-the time from the first day of your period to the first day of the next period. A normal menstrual cycle can be anywhere from 21 days to more than 35 days, but most girls have a period every 25 to 30 days.

For the first year or two, your cycle may not be regular. Your cycle can range from 21 to 40 days, and you may not have a period sometimes. If you are underweight because of dieting or exercise, have a lot of stress in your life, or are overweight, your periods may be hard to predict.