Common causes of irregular periods

Some women have periods that come like clockwork, and some women carry a pad with them at all times, just in case. A regular cycle for an adult woman can be anywhere from 21 to 35 days long with periods lasting between 2 and 7 days. There isn’t one perfect menstrual cycle, but there is such a thing as an irregular cycle.

If you have some of these symptoms, it’s possible that you have an irregular menstrual cycle:

  • Your periods happen less than 21 days or more than 35 days apart
  • Your periods last longer than seven days
  • You miss three or more periods in a row
  • Your menstrual flow becomes much lighter or heavier than usual
  • You have pain, severe cramping, nausea, or vomiting with your periods
  • You bleed or spot between periods, after menopause, or following sex

Irregular cycles can occur for many reasons. Sometimes you’re born with conditions that lead to an irregular cycle, and sometimes there are lifestyle elements that impact your cycle. Some of the most common causes of irregular periods include the following.

Hormone imbalances

Hormones like estrogen and progesterone work together to make ovulation and menstruation happen, and if you have an excess or deficiency of any of these hormones, it could cause irregularities. Hormonal imbalances may also result in anovulation, a condition where you don’t ovulate and therefore don’t have a true menstrual cycle. You could also have hormone imbalances that still allow you to ovulate, just not regularly.

Medical conditions

Conditions such as uterine polyps or fibroids, endometriosis, pelvic inflammatory disorder, polycystic ovary syndrome, and premature ovarian insufficiency can all lead to irregular periods. So can different bleeding disorders, thyroid problems, complications associated with pregnancy, miscarriage, and ectopic pregnancy.


If your body goes through significant changes, your menstrual cycle could be disrupted and become irregular. Being too overweight or too underweight, starting or stopping exercise routines, and other changes can impact your body and cause your cycle to be irregular. Other lifestyle factors that can change your cycle are travel, illness, smoking, emotional stress, and the consumption of excess caffeine or alcohol.


Although birth control is often prescribed to help regulate a menstrual cycle, it also has the potential to disrupt a cycle. Going on or off birth control pills can make your period irregular, and some forms of birth control will stop your period completely. Taking steroids or blood thinners can also impact your cycle.

Natural changes

There are also, of course, some extremely common reasons for an irregular or absent menstrual cycle: pregnancy, breastfeeding, or menopause. Sometimes the simplest answer is the correct one.

If you have any concerns about your menstrual cycle, don’t hesitate to make an appointment with your healthcare provider.

  • “Abnormal menstruation.” Cleveland Clinic. The Cleveland Clinic Foundation. 2015. Web.
  • Mayo Clinic Staff. “How can I track my menstrual cycle?” Mayo Clinic. Mayo Clinic. May 11, 2016. Web.
  • Jacqueline Thielen. “Many possible causes of irregular periods.” Mayo Clinic News Network. Mayo Clinic. September 16, 2011.
Get the Ovia Fertility app
Get our app at the Apple App Store Get our app at the Apple App Store Get our app at the Google Play Store Get our app at the Google Play Store