It's normal for periods to come early or late, or be heavy or light once in a while. But if this happens often, it's called irregular periods.

When periods first start, they may not come on a regular schedule. Or they may be regular at first and then become irregular. If periods don't become regular, treatment may be needed. Use these instructions to care for your child.

• Encourage your child to track their periods on a calendar. Include:
  • The day each period begins and ends.
  • If the flow is heavy or light on each day.
  • Any other problems such as cramps, belly pain, or headaches.
• Take your child to get any lab tests done that the health care provider ordered.
• Go to any follow-up care visits as recommended by your health care provider.
• Females with irregular periods can still get pregnant. They can also get STDs (sexually transmitted diseases; also called STIs or sexually transmitted infections). Talk with your child about the importance of using latex condoms correctly every time they have sex. 

Your child:

• has periods that last longer than 7 days, are heavy, or come more often than every 21 days
• has periods that come less often than every 45 days
• has bleeding between periods
• gets new or worsening acne
• has extra hair growth on the face, chin, chest, or belly
• has severe cramping or belly pain
• got their first period more than 2–3 years ago and still has irregular periods
• stops having periods

How often should periods come? A regular period cycle is usually every 21–45 days. Usually, periods last 2–7 days.

What causes irregular periods? After they start, it can take up to a few years for periods to become regular. Irregular periods also can happen because of:

• a hormone imbalance
• having a very high or low body weight
• exercising too much
• an infection
• a long-term illness
• certain medicines
• pregnancy

How are irregular periods treated? In females who just started getting their periods, health care providers usually wait to see if the periods become more regular on their own. Treatment, if needed, it may include oral contraceptives ("the pill"), which can balance hormones and make periods come on a regular cycle, or other medicines. Treatment recommendations also can include changing eating or exercising patterns, or reducing stress.