Irregular Periods: Understanding 7 Potential Causes

Every time a woman has her period, her uterine lining (endometrium) gets ready to welcome a developing embryo or fetus. A normal menstrual cycle lasts anywhere from three to eight days, and if fertilization does not occur, the body will expel the endometrium during that time. Periods are normal for most women, but they are considered abnormal if they are too light, too heavy, happen too frequently, last too long, are irregular, or take place after menopause.

When Does a Period Become Irregular?

The average length of time between the beginning of one period and the beginning of the next is between 21 and 35 days.

Most of us believe a cycle of 28 days is typical, but there is actually some flexibility for variation. If your periods seem to be coming and going at odd times, try counting backward from the first day of your next period to see if you reach your last period. 

This process should be repeated monthly for three months. When the time span between the end of one period and the beginning of the next is significantly longer or shorter than the normal range of 21–35 days, the person is said to have an irregular cycle. If the length of your menstrual cycle fluctuates by more than 20 days from month to month, your periods may be considered irregular.

Why do menstrual cycles fluctuate?

1. Medications

Hormone replacement therapy, anticoagulants, and anti-inflammatory drugs can all have an impact on menstrual flow. Birth control methods utilizing intrauterine devices (IUDs) have been linked to abnormally heavy menstrual bleeding.

2. Hormone imbalances

Estrogen and progesterone control how much of the uterine lining is produced. Heavy bleeding is possible if these hormones are produced in excess. Girls who have only recently started menstruating are particularly vulnerable to hormonal imbalances. They also tend to crop up in women who are on the cusp of entering menopause.

3. Significant medical issues.

A few examples of these are:

  • Ovary cysts and polycystic ovary syndrome (PCOS): Overproduction of “male” hormones (androgens) by the ovaries or adrenal glands, combined with insulin resistance, causes this metabolic and hormonal disorder.
  • Thyroid or pituitary disorders: Menstrual regularity can be impacted by hypothyroidism, hyperthyroidism, and hyperprolactinemia.
  • Inflammatory disease of the pelvis (PID): PID is an inflammation of the female reproductive system caused by a virus or bacteria that is typically transmitted sexually.

4. Stress

The stress hormone, cortisol, can interfere with hormone production. The degree of impact is proportional to the intensity of the stress.

Your period may be delayed by a few days if you experience a sudden burst of stress, but it may become increasingly irregular and even stop altogether if you experience prolonged, severe stress.

5. Birth control and other medications

It’s probably no secret that hormonal birth control relies on estrogen, progestin (synthetic progesterone), or a combination of the two to stop an egg from being released. Therefore, for many people, birth control pills or an intrauterine device (IUD) can help balance hormones, resulting in more regular menstrual cycles.

Contraceptives that alter hormone levels may also disrupt menstrual cycles. This typically occurs when a woman begins or stops using contraception. Getting back to regular period cycles after stopping birth control may take several months.

6. Milk production and breastfeeding

The menstrual cycle may change as a result of breastfeeding or lactation. Those who don’t breastfeed their babies can expect their periods to return earlier than those who do. The hormone prolactin, which causes lactation, inhibits the production of luteinizing hormone, which causes ovulation.

Thus, the more you breastfeed or pump, the more prolactin is produced, and the greater the likelihood that your period will be irregular or suppressed.

7. Unusually strenuous workouts

As with other hormones, those that regulate menstruation can be disrupted by engaging in excessive physical activity. This is not uncommon in women who train vigorously, such as athletes, dancers, and others. The “female athlete triad,” which may occur if extreme exercise is combined with a calorie-restricted diet, consists of:

  • Improper eating habits
  • Menstrual changes
  • The deterioration of bone mass is also known as osteoporosis. This is often the case for ballet and gymnastics dancers who feel social pressure to maintain an unrealistically thin physique. Having a lower body weight may provide a performance advantage in some contexts. The medical term for those who can’t seem to stop working out is “compulsive exercisers.”

When to see a doctor

Period irregularity is common because hormone levels are dynamic and can fluctuate significantly over the course of a lifetime. However, there are conditions in which you really should see a doctor. For medical assistance, please contact your doctor or consider visiting Merrick Ave urgent care if you are experiencing:

  • You have an annual absence rate of 33.3%
  • Your period has been regular up until now, but now it’s irregular.
  • You get your period more frequently than once every 21 days.
  • After waiting 35 days, you finally get your period.
  • You experience severe pain or heaviness during your periods.
  • A week or more has passed since your last period.
  • If your period pattern has always been regular but has recently changed, you should see a doctor. If you want, they can examine you and make sure nothing is physically wrong.


It’s normal to have a few irregular periods each year without any cause for alarm. But there are times when there is a good reason for a late period. It’s a good idea to rule out pregnancy before making an appointment with the best gynecologist.


1. What age do irregular periods start?

At some point in your forties, you may begin to experience the symptoms of menopause, such as menstrual irregularity. On the other hand, some women report changes as early as their mid-30s.

2. Why do periods change dates?

Your menstrual cycle and periods will change and develop over the course of your life as a result of age-related hormonal shifts and other factors like stress, lifestyle, medications, and health issues.

3. Can a lack of sleep cause a delayed period?

In particular, sleep deprivation affects levels of both stress hormones and the sleep hormone melatonin. The hormone melatonin plays a role in controlling when your period begins and how long it lasts. That’s why fluctuating melatonin levels can mess with your menstrual cycle.

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