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Reasons for Missed, Late or Irregular Periods

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Pregnancy is by far the most common cause of a missed period, but there are some other medical and lifestyle factors that can affect your menstrual cycle. Extreme weight loss, hormonal irregularities, and menopause are among the most common causes if you're not pregnant.

You may miss a period for one or two months, or you may experience complete amenorrhea—that is, no period for three or more months in a row. This article explores 10 common reasons your period may be delayed.

 Late or Irregular Periods


Intense stress interrupts the production of gonadotrophin-releasing hormone (GnRH)—a hormone that regulates ovulation and the menstrual cycle.

Both physical and psychological stress can cause a delayed period. But the level of stress capable of causing this effect is usually more severe than having a bad hair day.

Missing one period while going through a very stressful situation is not uncommon. However, if you're under prolonged stress and miss more than one period, consider scheduling a visit with your doctor.

If there is no other medical reason for your missed period, your doctor may suggest counseling to help you cope with your situation. Once your stress is back to a manageable level, it may take a few months or more for your cycles to become regular again.

Extreme Exercise

Extreme exercise can cause changes in pituitary hormones and thyroid hormones, which can impact ovulation and menstruation. Working out for one or two hours per day shouldn't affect your menstrual cycle. It takes hours upon hours of demanding exercise every day for these hormonal changes to occur.

If you are planning on exercising that much, you may want to consult with a sports medicine doctor. Their job is to help your body support all of the physical demands that you are putting on it. This may include:

  • Optimizing your diet with nutritious foods that boost your energy
  • Teaching you stretching techniques to reduce physical stress
  • Performing blood tests to check for iron or vitamin deficiencies, hormonal imbalances, dehydration, and more


Chronic conditions that can affect your menstrual cycle include:

  • Thyroid disease
  • Polycystic ovary syndrome (PCOS)
  • Pituitary tumors (which may or may not be cancer)
  • Diseases of the adrenal gland
  • Ovarian cysts
  • Liver dysfunction
  • Diabetes

Certain conditions that are present at birth, such as Turner syndrome and androgen insensitivity, typically cause menstrual and fertility problems. These congenital conditions are often associated with amenorrhea.

Acute illness, such as pneumonia, a heart attack, kidney failure, or meningitis, can result in rapid weight loss, nutritional deficiency, or hormone dysfunction. These conditions can also result in a missed period.


Many illnesses and disorders can interfere with your cycle until they are treated. Once the underlying condition is resolved, it might take a few months before your period returns again.

A Change In Your Schedule

Changing schedules can throw off your body clock. If you frequently change work shifts from days to nights, or if your schedule is generally all over the place, your period can be fairly unpredictable.

A change in your schedule shouldn't cause you to completely miss your period, but it can cause your period to start earlier or later than expected. Your cycle can also change by a few days if you experience jet lag.


Some medications, such as antidepressants, antipsychotics, thyroid medications, anticonvulsants, and some chemotherapy medications, may cause your period to be absent or delayed.

Hormonal contraceptives like Depo-Provera, progesterone-only MiniPill, Mirena IUD, and Nexplanon can also influence your cycle.

Different types of contraceptives can affect your menstrual cycle in different ways. Some contraceptives are associated with heavy periods, some with light periods, and some with amenorrhea.

Weight Changes

Being overweight, underweight, or experiencing drastic changes in weight all impact your cycle.7 Obesity influences estrogen and progesterone regulation and may even lead to issues with fertility.

Very high body mass index (BMI) is associated with missed periods, and weight loss can help regulate the menstrual cycle for women who are obese.

Being severely underweight interferes with regular menstrual cycles as well. When the body lacks fat and other nutrients, it cannot produce hormones the way it should.

Women who have anorexia (very low caloric intake) or who burn far more calories with exercise than what they consume may experience amenorrhea. Typically, weight gain will help your periods to return.

Rapid weight changes due to illness, medication, or dietary changes may interfere with hormone production or release. In turn, this may cause you to miss one period or more.

Recently Started Periods

A normal menstrual cycle lasts from 21 to 35 days in healthy women, but it can vary. This is especially true for young women who are just starting to get their periods, or for women who have not had periods for several years and are starting again.

A young woman who has only had a few cycles may go months without another one until a regular pattern begins.And women who have not had a period due to contraceptive use, hormonal therapy, or illness may not resume regular, monthly periods right away.

Perimenopause and Menopause

Perimenopause is the period of transition between reproductive age to non-reproductive age. Your periods may be lighter, heavier, more frequent, or less frequent during this time. In most cases, they'll just be different than what you're used to.

Menopause is when you have reached the point in your life where you will no longer ovulate or menstruate. The average age of menopause is 51 years old.

You may have light periods, infrequent periods, or amenorrhea when breastfeeding, particularly if breastfeeding provides your baby with all or almost all of their calories.

Many women believe that breastfeeding is a form of birth control, but it's not. Even if you don't have periods when you are breastfeeding, you can get pregnant. If you are not ready for another child, you should still use a contraceptive.

Ectopic Pregnancy

If you think that you can't be pregnant because you have an IUD, there is a small chance that your missed period could be a sign of an ectopic pregnancy.

Ectopic pregnancy can sometimes happen due to the shape of the IUD, and you may not test positive on a pregnancy test, either. Your doctor can check for it with a pelvic examination or an ultrasound.

Symptoms of ectopic pregnancy include cramping in your lower abdomen, shoulder pain, weakness or dizziness, nausea, and breast tenderness. Some women have missed periods, while others have vaginal bleeding or spotting.

In addition to the use of an IUD, other factors that are associated with ectopic pregnancy include:14

  • Endometriosis
  • Pelvic inflammatory disease
  • Progestin-only birth control pills
  • History of sexually-transmitted infection
  • History of infertility
  • In vitro fertilization
  • Birth defects of the fallopian tubes
  • Fallopian tube scarring, possibly due to pelvic surgery or appendix rupture

Ectopic pregnancy is a life-threatening condition. Seek medical attention right away if you miss your period and think you might be at risk.

When to Call Your Doctor

Missing a period every once in a while is usually not cause for concern. That said, you should see a doctor if you miss more than one period, or your missed period is accompanied by new or unusual symptoms.

Seek medical attention right away if you also experience any of the following:

  • New or worsening headaches
  • Vision changes
  • Nausea or vomiting
  • Fevers
  • Hair loss
  • Breast discharge or milk production
  • Excess hair growth


There are many reasons for late periods, and while most are not cause for alarm, you do need an evaluation and treatment if you have completely missed more than one period.

How your missed periods are treated depends on why you aren't having your period. The treatment can include lifestyle changes, such as diet or stress reduction, or may involve hormone replacement therapy.

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