How Long and How Much?

The amount of time that a girl has her period also can vary. Some girls have periods that last just 2 or 3 days. Other girls may have periods that last 7 days. The menstrual flow — meaning how much blood comes out of the vagina — can vary widely from girl to girl, too.

Some girls may be concerned that they're losing too much blood. It can be a shock to see all that blood, but it's unlikely that a girl will lose too much, unless she has a medical condition like von Willebrand disease. Though it may look like a lot, the average amount of blood is only about 2 tablespoons (30 milliliters) for an entire period. Most teens will change pads 3 to 6 times a day, with more frequent changes when their period is heaviest, usually at the start of the period.

Especially when menstrual periods are new, you may be worried about your blood flow or whether your period is normal in other ways. Talk to a doctor or nurse if:

• your period lasts longer than a week
• you have to change your pad very often (soaking more than one pad every 1-2 hours)
• you go longer than 3 months between periods
• you have bleeding in between periods
• you have an unusual amount of pain before or during your period
• your periods were regular then became irregular

Cramps

Some girls may notice physical or emotional changes around the time of their periods. Menstrual cramps are pretty common — in fact, more than half of all women who menstruate say they have cramps during the first few days of their periods. Doctors think that cramps are caused by prostaglandin, a chemical that causes the muscles of the uterus to contract.

Depending on the girl, menstrual cramps can be dull and achy or sharp and intense, and they can sometimes be felt in the back as well as the abdomen. These cramps often become less uncomfortable and sometimes even disappear completely as a girl gets older.

Many girls and women find that over-the-counter pain medications (like acetaminophen or ibuprofen) can relieve cramps, as can taking a warm bath or applying a warm heating pad to the lower abdomen. Exercising regularly throughout the monthly cycle may help lessen cramps, too. If these things don't help, ask your doctor for advice.