I’m 14 years old and sometimes my period is late, usually by a few days or a week. I’m definitely not pregnant, so why is this happening?

Great question! It’s very common for teens to have irregular or late periods, especially in the two years after their first period (also called menarche). With time, your body will begin to get used to these new hormones, and your menstrual cycle will most likely get more predictable.

The menstrual cycle is the hormonal process where your body prepares for a possible pregnancy.

The average cycle (from the first day of one period to the first day of the next) lasts 28 days. But that’s only the average. In reality, most people do not have menstrual cycles that last exactly 28 days. In fact, teens’ menstrual cycles can last anywhere from 21 to 45 days! The length of your menstrual cycle may change from one cycle to the next, and you may even skip periods at first. The length of your period may also change, though they typically last 3-8 days. After around two years, your periods will most likely begin to get more predictable.

Your period could also be late for other reasons.

Your menstrual cycle can be affected by changes in how much you exercise, what you eat, your weight, how stressed you feel, or the medications you take. Birth control can also affect your periods. Sometimes, irregular periods can be a sign of a hormonal imbalance. Talk to your health care provider if…

  • Your period stops, or you’ve missed it for more than 3 months.
  • Your period lasts longer than 8 days.
  • Your period was regular, but then became irregular.
  • Your period has been irregular for over 3 years.
  • Your periods are less than 21 days apart, or more than 45 days apart.
  • Your period is very painful, and can’t be managed with over-the-counter pain medication like ibuprofen.
  • You bleed enough that you need to change your pad, tampon or menstrual cup more than once every 2 hours.

Your health care provider can help you figure out if something else is going on, and (if necessary) prescribe medication to help your periods become more regular.

Even though you say you’re definitely not pregnant, you should also talk to your health care provider if you’ve had penis-in-vagina (PIV) sex and your period is late.

We know it can be annoying when periods don’t come when you expect them! In the meantime, keep a pad or tampon in your bag in case your period catches you by surprise.

If you’re 10-22 years old in NYC, you can get free, confidential health care at the Mount Sinai Adolescent Health Center. Just call 212-423-3000 for an appointment. No immigration restrictions, no insurance needed.