A period can be late for many reasons, including changes in a person’s dietary or exercise regime. A person may choose to take a pregnancy test if their period is late. However, the result can be negative if a person is pregnant but takes the test too soon.

The ovaries release an egg during ovulation, approximately every 28 days. If no sperm fertilizes the egg, a person’s period will usually start about 14 days later.

While a missed period is one of the first signs of pregnancy, there are various other reasons why it can occur.

Menstrual irregularities, such as missed or late periods, occur in 14–25% of women of childbearing age. They can result from a range of conditions besides pregnancy, including hormonal imbalances, hormonal birth control, stress, weight loss, trauma, and certain health conditions.

This article discusses what can cause a person to miss their period and how common this is.

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Irregular periods are common, especially during the first few years of a person’s period. Many circumstances may affect the regularity of the menstrual cycle, including:

Weight changes due to an eating disorder

The rapid gain or loss of a significant amount of weight can lead to hormonal imbalances. Eating disorders such as anorexia nervosa may cause dysfunction in the hypothalamic-pituitary-ovarian axis, which causes changes to hormone levels and may cause periods to be irregular or stop altogether.

Help is available

Eating disorders can severely affect the quality of life of people living with these conditions and those close to them. Early intervention and treatment greatly improve the likelihood of recovery.

Anyone who suspects they or a loved one may have an eating disorder can contact the National Alliance for Eating Disorders, which offers a daytime helpline staffed by licensed therapists and an online search tool for treatment options.

For general mental health support at any time, people can call the Substance Abuse and Mental Health Services Administration 24 hours a day at 1-800-662-4357 (or 1-800-487-4889 for TTY).

Many other resources are also available, including:

Stress

Intense stress can affect the part of the brain that controls the reproductive hormones. This can cause ovulation and periods to stop.

Once the cause of the stress eases or the person learns coping strategies to manage it, their regular cycle may return.

Producing too much prolactin — breastfeeding

Prolactin is a hormone that the body usually makes during breastfeeding. It can affect menstruation and is why most people who breastfeed do not have periods. Periods typically return once a person stops breastfeeding.

A milky discharge from the nipples can signify that the body is making an abnormally high amount of prolactin in people who are not breastfeeding. Doctors can treat excessive prolactin production with medication.

Polycystic ovary syndrome (PCOS)

People with PCOS have a hormonal imbalance that can affect their overall health and appearance, in addition to causing ovarian cysts. This can cause a person to have irregular periods or stop having them entirely.

Up to 10% of women of childbearing age have PCOS and may have enlarged ovaries with clusters of small, benign cysts.

People with PCOS may experience other symptoms as well as missing periods. These include:

  • very light, very heavy, or unpredictable bleeding during periods
  • skin conditions, such as acne, dark patches, or skin tags
  • being overweight or having obesity
  • thinning hair
  • sleep apnea
  • difficulty getting pregnant
  • excess hair on the face, back, or thighs
  • increases in vaginal discharge
  • cramping

Excessive exercise

Amenorrhea is common among athletes who train intensely. Intense exercise causes the body to release stress hormones, which can interfere with the production of reproductive hormones and cause irregular or missed periods.

Exercises that may cause a person to have low body weight, such as long-distance running or intensive ballet, are more likely than others to cause amenorrhea.

Hormonal birth control

Hormonal birth control works by suppressing ovulation, which means a person may experience changes to their period, including having periods that are early, late, or stopped altogether.

Some underlying health conditions may cause a person to stop having periods altogether.

Thyroid problems

The thyroid is a gland that produces hormones to control the body’s metabolism.

Hypothyroidism, or an underactive thyroid, is when the thyroid does not produce enough of these hormones. Hyperthyroidism, or an overactive thyroid, results in the levels of thyroid hormones in the body being too high. Both conditions can affect the frequency of a person’s period.

Doctors can usually diagnose thyroid problems using a simple blood test.

Thyroid disorders can cause a person to miss their period but may also cause other symptoms, including;

  • fatigue, or extreme tiredness
  • hair loss
  • unexplained weight gain or loss
  • always feeling cold or being warm all the time

Perimenopause

People enter menopause when they have not had a period for at least 12 months. The average age of people entering menopause in the United States is 52 years old. However, the transition to menopause, known as perimenopause, may cause symptoms that begin at a younger age.

Other symptoms of perimenopause include:

  • heavier or lighter periods
  • hot flashes
  • problems sleeping
  • mood swings or irritability
  • vaginal dryness
  • reduced interest in sex

Diabetes

People with type 2 diabetes are at an increased risk of irregular menstrual periods due to anovulation, which happens when an ovary does not release an egg into the fallopian tube. When this occurs, a person will not get their menstrual period.

Primary Ovarian Insufficiency (POI)

POI is when a person’s ovaries stop working as expected before they reach 40 years old. POI is not the same as early menopause or perimenopause. People with POI may not get their monthly periods or may experience irregular periods.

Cushing’s syndrome

Cushing’s syndrome is a hormonal condition that occurs due to exposure to too much cortisol or medications similar to cortisol. People with Cushing’s syndrome may experience irregular or stopped periods.

Some people may experience vaginal discharge alongside missed periods.

Potential causes of this include:

In some instances, a person may experience abdominal cramps and missing periods.

Potential causes of this include:

Home pregnancy tests can sometimes give a false negative result, indicating that someone is not pregnant when they are. The accuracy of a home pregnancy test varies depending on how and when a person takes it.

Some of the reasons a test may give a false-negative result include:

Taking a test too soon

Home pregnancy tests look for the presence of human chorionic gonadotropin (hCG) in urine. Although some tests can detect hCG from the first day of a missed period, they are generally more accurate later on.

Low hormones

Tests are usually more precise first thing in the morning because the urine is less diluted at this time, making hCG easier to detect.

If a person starts to experience irregular periods, they should contact their doctor immediately. This includes having periods more frequently than every 24 days or less often than every 38 days.

Individuals may miss a period due to several causes, including specific medical conditions, so it is essential to get a proper diagnosis.

To ensure that a home pregnancy test is accurate, people should follow the instructions on the packaging and wait until at least 1 week after the first day of the missed period before taking the test.

Menstrual irregularities such as missed or late periods are common, especially in younger people who are menstruating. If a person misses a period and is not pregnant, it could be due to situational factors such as increased stress, intense exercise, starting new hormonal birth control, or experiencing sudden weight changes.

In some cases, a missed period may be due to a chronic condition such as a thyroid condition, type 2 diabetes, Cushing’s syndrome, or PCOS.

If a person misses more than three periods in a row, they should contact a healthcare professional to make sure their reproductive system is healthy and functioning properly.