What Causes Irregular Periods? - Crozer-Keystone Health System - PA

Irregular Periods

Most women with a regular cycle have between 11 and 13 menstrual periods each year. However, women’s bodies are forever changing. From time to time, every woman suspects that her menstrual cycle is abnormal for one reason or another.

It’s important to remember that each woman’s cycle is different, so your “normal cycle” may not be the same as your best friend’s “normal cycle.” There are, however, some common reasons for a period to be irregular.

Because each woman’s cycle is different, and because there are so many factors that cause an irregular cycle, it can sometimes be hard to pinpoint an exact reason for the irregularity. Periods are often irregular during the first couple of years of menstruation. This is because the body is still developing the delicate hormonal balance that leads to a regular cycle. Another common cause of an irregular or missed period is pregnancy.

What Causes Irregular Periods?


During the first few years after menstruation starts, periods are often irregular while the hormones that control menstruation reach a balance. They may also be irregular at the end of menstrual years when women reach perimenopause and menopause – menopause starts when it’s been 12 months since a menstrual period.

Those irregularities are normal and common. But there are other times in women’s lives and other conditions that can lead to irregular menstrual cycles.


The most common cause of a missed period is pregnancy. Until you know for sure if you’re pregnant or not, you should treat yourself as though you are. This is one instance when you should call your OB/GYN or midwife. You can use an at-home pregnancy test, but your healthcare provider can use other tests to determine whether you’re pregnant and how far along you are, in addition to informing you on what else you should be doing for a healthy pregnancy.

Medical Conditions

Two common causes of irregular menstrual periods are polycystic ovary syndrome (PCOS) and hypothyroidism.

PCOS is a hormone imbalance that can affect ovulation, cause issues with a woman’s period and make it more difficult to get pregnant. If your doctor determines this is the cause of your irregular periods, treatment may include birth control pills or other hormones to restore hormonal balance.

Hypothyroidism, a.k.a. underactive thyroid disease, is caused by your thyroid gland not producing enough of its hormone. Similar to PCOS, treating hypothyroidism involves supplementation of thyroid hormones.

Lifestyle Conditions

If you are not pregnant, other common causes of an irregular period include:

  • Excessive weight loss or gain: although low body weight is a common cause of missed or irregular periods, obesity also can cause menstrual problems
  • Eating disorders, such as anorexia or bulimia
  • Increased exercise: missed periods are common in endurance athletes.
  • Emotional stress
  • Medicines such as birth control methods, which may cause lighter, less frequent, more frequent, or skipped periods or no periods at all
  • Hormone problems: this may cause a change in the levels of the hormones that the body needs to support menstruation
  • Illegal drug use
  • Problems with the pelvic organs , such as imperforate hymen, polycystic ovary syndrome, or Asherman’s syndrome
  • Breastfeeding: many women do not resume regular periods until they have completed breastfeeding.

Call your doctor or midwife if you miss three or more periods a year, get your period more often than every 21 days, get it less than every 35 days, if you’re bleeding more heavily than usual during your period, if you bleed for more than seven days, or if you have more pain than usual during a period.

It’s always best to be proactive when it comes to your health, something women can often forget when running their busy lives. Getting something checked out can help to prevent serious health conditions later on down the road.

Treatment Options for Irregular Periods

Although treatment depends on what is causing your missed periods, it’s important to treat any underlying conditions or diseases that may be causing your irregular periods, since they could lead to more serious complications.

There are a number of common treatment options that can help regulate your cycle. Some of the most common options for women with irregular periods include:

  • Maintaining ideal body weight
  • Weight loss if you are overweight
  • Weight gain if you are underweight
  • Eating more calories if you suffer from eating disorders
  • Decreasing excess and/or strenuous exercise
  • Stress reduction
  • Birth control pills
  • Medicines that help with pregnancy and fertility
  • Hormones if you are going through early menopause
  • Surgery if you have problems in the reproductive system

If you typically have regular, monthly menstrual periods and the pattern changes, your doctor can perform an exam and run blood tests to check your hormone levels and thyroid function – these can rule out pregnancy or a health issue.

Warning Signs of an Oncoming Period

So, if your cycle is irregular, how can you tell when you're about to get your period? Below are some clues your body may give you, according to the National Institutes of Health:

  • Back cramps or stiffness
  • Heavier breasts or breast soreness
  • Headaches
  • Acne breakouts
  • Disturbed sleep patterns
  • Mood swings
  • Bloating


Women may also find that their menstruation cycle is changing before menopause. Women can experience age-related menstrual changes as early as their 30's. Some of the changes that women can experience include:

  • A change in periods - shorter or longer, lighter or heavier, with more or less time in between
  • Hot flashes and/or night sweats
  • Trouble sleeping
  • Vaginal dryness
  • Mood swings
  • Trouble focusing
  • Less hair on head, more on face.

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