5 Most Common Causes Of Irregular Periods

5 Most Common Causes Of Irregular Periods

At least 30% of women have irregular periods during their childbearing years.

Your menstrual cycle may not always be like clockwork. While some women get their periods right on schedule every 28 days, other women’s cycles aren’t so predictable.

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.

At least 30% of women have irregular periods during their childbearing years, gynecologists report. While an irregular cycle is not usually a problem, it can occasionally signal health complications.

If your menstrual cycle is irregular from time to time, it's probably no big deal. But do you know how to tell if you have reason to be concerned? Keep reading to find it out.

When is a cycle irregular?

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. When menstruation first starts, it can take up to 2 years to establish a regular cycle.

Also, periods may stop becoming regular up to 8 years before menopause.

In adults, a normal menstrual cycle lasts 28 days, plus or minus 7 days. Menstrual bleeding is considered irregular if it occurs more frequently than every 21 days or lasts longer than 8 days. Missed, early, or late periods are also considered signs of an irregular cycle.

To determine whether your menstruation schedule is irregular, count from the last day of your previous period and stop counting on the first day of your next.

Repeat this for 3 months.

If the number of days between stopping and starting your period is significantly different each month, you have an irregular cycle, doctors say.

A symptom of irregular menstruation is also when the cycle is longer than 35 days.

If there are changes in blood flow, or if clots appear that are more than 2.5 centimeters in diameter, this is also considered irregular.

Why it happens

The following factors can trigger irregular or missed periods.

Extreme exercise

Exercising too much can throw off the timing of menstrual bleeding and sometimes stop it. Intense or excessive exercise has been shown to interfere with the hormones responsible for menstruation.

It’s common for endurance athletes to have missed periods, gynecologists note. Female athletes and women who participate in intensive training and physical activities, such as ballet dancers, often develop amenorrhea, which is missed or stopped periods.

Weight disorders

Women with conditions like anorexia or bulimia may have irregular or missed periods because their bodies are not producing and circulating enough hormones to control the menstrual cycle, according to the Hormone Health Network.

Being underweight, whether from extreme exercise, dieting, an eating disorder, or illness, can have the same effect.

Although low body weight is a common cause of missed or irregular periods, obesity also can cause menstrual problems. Research shows that being overweight impacts hormone and insulin levels, which can interfere with your menstrual cycle.


Chronic stress or even short-term anxiety about a specific problem can wreak havoc with your hormone balance, causing a missed period and irregular cycle.
Research shows that stress can interfere with your menstrual cycle by temporarily interfering with the part of the brain that controls the hormones that regulate your cycle.

Your periods should return to normal after your stress decreases.

Thyroid problems

The thyroid gland produces hormones that affect the body’s metabolism.

Hypothyroidism, or underactive thyroid, can cause longer, heavier periods and increased cramping. You may also experience fatigue, sensitivity to cold, and weight gain.

High levels of thyroid hormones, which is seen in hyperthyroidism, can cause shorter, lighter periods. You may also experience sudden weight loss, anxiety and nervousness, and heart palpitations.

Swelling at the base of your neck is another common sign of a thyroid disorder.

Polycystic ovary syndrome (PCOS)

This is a condition in which a number of small, fluid-filled sacs known as cysts develop in the ovaries, interfering with regular ovulation.

Women with PCOS usually have a history of irregular periods. A woman with PCOS does not ovulate, and she does not release an egg every month.

Symptoms include irregular or no periods, obesity, acne, and excess hair growth.
In addition to causing infertility, PCOS can increase the risk of diabetes and heart disease.

When should you worry?

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 irregular periods.

A couple of irregular periods per year are usually nothing to worry about, experts say. Any more than that, and you should see a doctor to be sure an ovulation problem or health condition isn’t the cause.

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.

A gynecologist will be able to determine the cause of your irregular periods and help you figure out a treatment course.

It’s always best to be proactive when it comes to your health, something women can often forget when running their busy lives. A missed or irregular period may be the first clue that you have a condition that needs medical attention. Getting something checked out can help to prevent serious health conditions later on down the road.

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