Having irregular periods is common. However, frequent or large changes to a person’s menstrual cycle may indicate an underlying health condition. Possible causes of irregular periods include fibroids, stress, and more.

Doctors consider a person to have irregular periods if their cycles are longer than 38 days, or if the length of each cycle varies by more than 7–9 days.

Below are some potential causes of irregular periods, their symptoms, and their treatments.

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Pregnancy stops a person from having periods. A missed period or spotting instead of a period can be the earliest sign. Other signs of early pregnancy may include:


If a person’s period is late, they might take an over-the-counter pregnancy test or request testing from a doctor. If the result of a store-bought test is positive, consult a healthcare professional about the next steps.

Speak with a doctor as soon as possible if bleeding occurs after a positive pregnancy test, as this can be a sign of pregnancy loss or ectopic pregnancy. Ectopic pregnancies are life threatening without treatment.

Some signs of an ectopic pregnancy include:

  • pain in the pelvis or abdomen
  • nausea
  • vomiting
  • dizziness
  • fainting

Hormonal birth control works by suppressing ovulation. This means that a person does not have a true period. However, people who use hormonal birth control pills, patches, implants, and intrauterine devices, called IUDs, can still experience vaginal bleeding.

This bleeding may occur roughly once a month, like a regular period. Some people have spotting, irregular bleeding, lighter bleeding, or heavier bleeding after they start this form of birth control. For others, the bleeding stops entirely.

Irregular bleeding due to contraception is usually not harmful, but if a person finds it undesirable or wants to try something else, they can speak with a doctor.

Prolactin is a hormone that plays a role in breastmilk production. It can also suppress ovulation, especially in people who exclusively and frequently breastfeed during the first months of a baby’s life. This means that a person may not get periods during this time.

Doctors call this lactational amenorrhea. It is not harmful. Periods usually return shortly after a person starts breastfeeding less frequently or when they stop breastfeeding.

Perimenopause is the first stage of menopause, and it begins 4–8 years before menopause starts, usually when a person is in their 40s.

During perimenopause, the menstrual cycle may get longer or shorter at various points. Eventually, periods happen less often, and they stop altogether when menopause begins.

Other possible signs of perimenopause include:

  • hot flashes
  • night sweats
  • mood changes
  • difficulty sleeping
  • vaginal dryness

Identifying perimenopause

Doctors can identify perimenopause by performing blood tests. They may also perform tests to rule out other factors that can have the same effects, such as thyroid disease.

Menopause and perimenopause are natural stages of life, not health problems that require treatment. Some of the changes that they bring can be uncomfortable or distressing, however, and doctors can recommend ways to minimize the impact.

The right approach depends on the changes. For example, if a person experiences vaginal dryness, lubricants and vaginal moisturizers may help, while estrogen therapy may help with hot flashes.

High stress levels are associated with irregular periods. Scientists confirmed this in 2021 by conducting a retrospective study on cycle regularity during the COVID-19 pandemic.

Out of 210 participants, 54% reported changes in their menstrual cycles in the early months of the pandemic. Those with higher self-reported stress were more likely to have longer, heavier periods.

When a person is stressed, the body releases stress hormones, such as adrenaline and cortisol. These can interact with the sex hormones that regulate menstruation.

Diagnosis and treatment

In the short-term, stress can help people respond to threatening situations. However, chronic stress is harmful to mental and physical health.

A person who frequently feels stressed, for any reason, may find it helpful to speak with a mental health professional, who can talk feelings through and teach ways of reducing stress. There are many stress reduction techniques that people can try.

Learn more about why stress happens and how to manage it.

Irregular periods are the most common sign of polycystic ovary syndrome (PCOS), which occurs when cysts grow in the ovaries. People with this condition often have high levels of androgens, which are male sex hormones. This can stop ovulation, resulting in irregular periods.

People with PCOS may miss periods and have heavy bleeding when periods do arrive. Other symptoms include:

Diagnosis and treatment

There is no single test for PCOS, so a doctor bases the diagnosis on symptoms, blood test results, and an ultrasound scan to look for cysts on the ovaries.

The treatment depends on whether the person is trying to get pregnant. If they are, medication to induce ovulation may help.

Otherwise, hormonal birth control may help regulate the person’s cycle. Some people also find that their symptoms improve after they lose any excess weight, start avoiding high sugar foods, or both.

The thyroid is a butterfly-shaped gland in the neck that produces thyroid hormones. These have an influence on the menstrual cycle.

Having an underactive thyroid — a condition called hypothyroidism — means that the thyroid gland does not produce enough hormones. This can cause longer, heavier periods. Other symptoms include tiredness, sensitivity to cold, and weight gain.

An overactive thyroid, or hyperthyroidism, can cause shorter, lighter periods. A person with this condition may also experience unexplained weight loss, anxiety, and heart palpitations.

Diagnosis and treatment

To diagnose thyroid disease, a doctor requests a blood test that checks levels of thyroid hormones. They also ask about symptoms and take a medical history.

If a person has hypothyroidism, the doctor prescribes medication that replaces the missing thyroid hormones.

If someone has hyperthyroidism, the doctor may recommend medication to reduce thyroid function, radiotherapy targeting the thyroid, or the surgical removal of part or all of the thyroid.

Fibroids are growths that can develop in the wall of the uterus. Most fibroids are noncancerous. They can range from the size of an apple seed to the size of a grapefruit.

A person with fibroids may have periods that are painful and heavy enough to cause anemia. They may also experience:

  • pelvic pain or pressure
  • lower back pain
  • leg pain
  • pain during sex

However, some people have no symptoms aside from irregular periods.

Diagnosis and treatment

Most fibroids that do not cause symptoms do not require treatment.

Otherwise, a person may be able to manage the pain with over-the-counter medications. If someone has heavy periods, they may need an iron supplement to prevent anemia.

A doctor may recommend surgically removing larger fibroids that cause pain or other symptoms.

Endometriosis affects 1 in 10 females of reproductive age. It causes the tissue that usually lines the uterus to grow outside the uterus. This can cause significant pain, especially around menstruation.

Other symptoms include:

  • heavy bleeding
  • long periods
  • bleeding between periods
  • painful bowel movements
  • pain during or after sexual intercourse

Diagnosis and treatment

Exploratory surgery is the only way to diagnose endometriosis. There is currently no cure, but medication and hormone therapy can manage the symptoms.

People trying to become pregnant may need surgery to remove the tissue that is growing outside the uterus.

Excessive or rapid weight loss can cause periods to become less regular or stop. This happens when parts of the brain stop releasing hormones that impact the menstrual cycle. The medical term for it is hypothalamic amenorrhea, and it leads to an estrogen deficiency.

A person with underweight may develop:

  • dry skin or hair
  • thinning hair
  • tiredness
  • difficulty concentrating
  • difficulty getting warm
  • a low mood

Diagnosis and treatment

Using the body mass index (BMI), a person has underweight if their BMI is lower than 18.5. A doctor may calculate a person’s BMI to see if this could be the cause of irregular periods.

How doctors approach underweight depends on the cause. A person may have unintentionally lost weight, in which case, nutritional counseling may help. However, if the cause could be an eating disorder, the doctor may refer the person to a therapist for an assessment.

If a person finds it difficult to stop thinking about food or weight loss, or if they fixate on eating only “clean” or healthy foods, they need to speak with a medical professional. Seeking help can be hard, but it is important.

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:

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Excessive exercise can also interfere with the hormones responsible for menstruation. This can occur in female athletes, dancers, and others who train intensively. If intense exercise is combined with a restrictive diet, a person might develop the “female athlete triad,” which includes:

  • disordered eating
  • menstrual changes
  • low bone mineral density, or osteoporosis

This can result from pressure to be thin for people who participate in certain sports, such as ballet or gymnastics. In some cases, there may be a competitive advantage of having a lower body weight. Some people find it hard to stop exercising, and the medical term for this is compulsive exercise.

Diagnosis and treatment

A doctor may determine that exercise is causing irregular periods after asking about the person’s routine and diet. For some people, making changes to the exercise routine can help.

If disordered eating or compulsive exercise is the cause, the person may benefit from working with a mental health professional.

Certain medications can affect the menstrual cycle, including:

  • blood thinning medications, such as aspirin
  • nonsteroidal anti-inflammatory drugs, or NSAIDs, such as ibuprofen (Advil, Motrin)
  • thyroid medications
  • antidepressants
  • epilepsy drugs
  • chemotherapy drugs

Diagnosis and treatment

Medication-related changes to menstruation are not always harmful. However, if a person believes that their irregular periods are related to a medication, they may want to speak with a doctor about alternatives. A person should not adjust their dosage of any medication without consulting a doctor.

Cervical and endometrial cancers can cause unusual bleeding from the uterus that may resemble a period. A person may also notice bleeding between periods or after sex.

These types of cancer cause few symptoms in the early stages, so it is vital to speak with a doctor about any unexplained vaginal bleeding.

Diagnosis and treatment

To diagnose cervical or endometrial cancer, a doctor may take a tissue sample to send for analysis. They may also perform medical imaging tests, such as an ultrasound. Treatment for cancer may include surgery, chemotherapy, or radiation therapy.

People should speak with a doctor if they:

  • stop having periods for several months and are not pregnant
  • suddenly develop irregular periods, when these are usually regular
  • have a cycle that is shorter than 24 days or longer than 38 days
  • have a cycle that varies dramatically in length
  • experience bleeding between periods or after sex
  • experience bleeding after menopause
  • experience other symptoms, such as unusual vaginal discharge or fever

Keeping track of when periods occur can help people recognize any irregularity and spot patterns. For example, if someone starts birth control or experiences a stressful event, they may notice that this affects their period.

People can track periods in a diary, on a calendar, or with a period tracking app. Begin by marking the first day of a period, and continue marking the days when bleeding occurs. Within a few months, a person can tell if their periods are regular.

Some people also note down any symptoms, how light or heavy the bleeding was, and any factors that might have affected it. It can be useful to show this record to a doctor when speaking with them about irregular periods.

Irregular periods can result from a range of factors, including some medical conditions. Most causes of irregular periods are not serious, but some are. A doctor can determine the cause and suggest treatments or other approaches, if necessary.

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