10 Causes of Irregular Periods

A regular menstrual cycle, although at times quite inconvenient, is a sign of stability and consistency. Women depend on it, whether we realize it or not. So when it’s out of whack, it becomes quite a nuisance—most especially when the irregularity includes more bleeding, rather than less.


Women who skip periods altogether often take a little longer to show up in my office a tad later than those who tend to bleed more. Who wouldn’t mind being bothered less with an inconvenience? By inconvenience, I mean:

  • Heavier flow
  • Longer duration of bleeding
  • Spotting or bleeding in between periods
  • Shorter time span between bleeding

But skipping periods, especially for 3 months or longer at a time, can also be concerning. Women who skip periods can have a greater risk of developing endometrial cancer in their lifetime. So please do not ignore their absence, either.

What Is a “Normal” Period?

But what exactly is considered “normal”? Because there is a huge variation of bleeding, and every woman is different.

Cycle: This reflects the number of days between the first day of bleeding until the first day of your next period. A normal cycle can range anywhere between 21 and 35 days.

Duration: Normal periods last anywhere between 2 to 7 days.

Flow: This one is more of a challenge to define. Most women tell me that they go through 4-5 pads or tampons a day on average. However, what is most important is a change from your baseline. If your periods are heavier or lighter than usual, you should report this to your doctor.

Keep reading for 10 causes of irregular periods.

Causes of Irregular Periods

  1. Polycystic Ovarian Syndrome (PCOS): This is an underestimated and very common health condition affecting more than 1 in 10 women. A hallmark of this condition includes period problems. Most women who experience irregular periods actually suffer from an undiagnosed PCOS.  It is caused by higher circulating testosterone, a hormone that causes excess body hair, weight gain, acne, and problems with periods (see my prior post on “When to Worry About Body Hair” to learn more). This testosterone attacks the ovaries and wreaks havoc on the hormones. These patients often have family history of diabetes and also have a higher risk of developing diabetes themselves.
    Most women who experience irregular periods actually suffer from an undiagnosed PCOS.
  2. Hormonal Imbalances: Besides PCOS, there are a few other less common health conditions, such as thyroid disorders and disorders that cause an elevation in the hormone called “prolactin” that may cause irregular periods.
  3. Medications: Birth control, steroids, or anti-psychotic medications can cause periods to have a mind of their own.
  4. Stress: There really is a physiologic phenomenon called “Hypothalamic-Pituitary Amenorrhea,” a term referred to the absence of periods due to hormonal changes in the brain that tell the female body parts that you are too stressed out to have a baby. And your periods will stop in response.
  5. Eating Disorders: Eating disorders, such as Anorexia or Bulimia, also tell the brain that you are not healthy enough to carry a pregnancy, thereby shutting down your periods.
  6. Rigorous Exercise: Exercise is great for the heart and body. However, like everything in excess, it can do more harm than good. This is precisely the reason that athletes’ periods tend to cease. Again, it’s our body’s way of informing us that carrying a pregnancy is less than ideal.
  7. Pregnancy:  It may seem like a no-brainer. But pregnancy can certainly throw us off cycle. Pregnancy is by far the most common cause of skipping periods. However, it can sometimes induce abnormal spotting or bleeding, as well.
  8. Perimenopause: A common phenomenon for women in their 40’s are the years prior and leading up to menopause. Our estrogen levels gradually decline and hence our periods seemingly out of control. Average age of menopause in women is 51, and it is defined as one year without a period.
  9. Fibroids:  Also affecting about 40% of women in their 40’s, are these non-malignant tumors of the uterus. Do not let the term “tumor” scare you – this is a general term that refers to benign, non-cancerous growths as well. They shrivel away after menopause if you can hang. So you do not necessarily need to do anything with them. However, for some women they can cause more bleeding.
  10. Endometrial Cancer: For women over the age of 35 that bleed more in any way, this is the most perilous cause of period problems – although the least likely cause on this list. It is discovered with an endometrial biopsy, which is an office procedure in which a probe is placed through the opening of the cervix and sample of the lining of the uterus is taken and sent off to the pathology lab to be viewed under a microscope. The procedure is similar to a pap, but deeper.


Getting down to the root of the problem is not always easy. But besides a thorough history, along with a simple blood and/or urine pregnancy test is great start.  Make sure you are also up to date on your pap smears – note that pap smear screening frequency guidelines have changed, which I’ve reviewed in a prior episode. In addition, your doctor may consider a pelvic ultrasound and/or endometrial biopsy in certain instances.

Please note that all content here is strictly for informational purposes only.  This content does not substitute any medical advice, and does not replace any medical judgment or reasoning by your own personal health provider.  Please always seek a licensed physician in your area regarding all health related questions and issues.

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