What Causes Irregular Periods

Period Calender

Irregular Periods can be confusing! If you think your period seems different, check out these reasons why it may seem off – and what to do about it.

Irregular periods can be scary, but there is nothing to worry about. There are lots of reasons why your period may not show up on cue. Remember, it is always best to talk to your doctor if you have any concerns. In the meantime, we will try to help you understand some reasons why your periods may have changed and the causes of having irregular period.

Is this Common?

It is common to have irregular periods every now and then, especially if you have just started your periods in the last few years. It takes a few years from when you begin for your periods to become regular.

Have you been having periods for many years? Your cycle may get shorter near age 35 and often gets shorter as you near menopause (around age 50). It is also normal at that age to skip periods or for the amount you bleed to change. Make sure that you talk to your doctor to get all the details about the causes of irregular periods.

It is important to know, too, that "irregular" is a personal word: You know your cycle well enough to know what is normal for you and what seems not, so you are the best judge.

Causes of Abnormal Menstrual Bleeding and an irregular menstrual cycle

There are a lot of things that can cause heavy bleeding or an irregular menstrual cycle, so you probably need to visit to your doctor to make sure that you are alright.

Your doctor may start by checking for problems most common for your age. A few of the most common reasons of irregular period are:

  • Miscarriage
  • Fibroids, which is benign tumours made up of muscular and fibrous tissue
  • Problems with blood clotting
  • Polyps, which is small (usually benign) growths with a stalk that protrude from a mucous membrane (yeah, sounds pretty weird to us, too!)
  • Chronic medical conditions (like thyroid problems, for example)

Unusual Bleeding

Unusual bleeding is when you bleed outside your cycle. Just like heavy bleeding and an irregular menstrual cycle, it is a good idea to talk to your doctor about your bleeding symptoms if they just seem to come out of the blue.

Is Heavy Menstrual Bleeding Dangerous?

Any heavy bleeding can cause you to lose iron, which will leave you feeling weak and tired. Sometimes you might have dark, thick blood on your heaviest flow days, but if you do not usually bleed heavily, or it lasts longer than it usually does, then, it is time to head to the doctor. Heavy bleeding beyond what is usual for you is definitely a medical issue or even an emergency. And it is best to check out the causes of irregular periods, too.


  • ACOG Pamphlet 95 : Abnormal uterine bleeding