If someone’s menstrual cycle is shorter than 24 days, more than 38 days long, or if the length varies significantly from month to month, they have irregular periods. Doctors call this oligomenorrhea.

This information comes from the Office on Women’s Health.

It is normal for the menstrual cycle length to vary slightly from month to month, especially if someone is going through puberty, breastfeeding, or approaching menopause.

Many other factors can affect period regularity, too, such as stress, medications, and mental or physical health conditions.

In this article, learn more about irregular periods, including the causes and treatment.

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Irregular periods, or oligomenorrhea, can occur for many reasons. Many relate to hormone levels.

Estrogen, progesterone, and follicle-stimulating hormone are the main hormones responsible for regulating the menstrual cycle. If something disrupts or alters how these hormones rise and fall each cycle, it can cause irregular periods.

Occasional irregular periods are common and are not usually cause for concern. Factors that may contribute to irregular periods include:

  • natural hormonal shifts
  • hormonal birth control
  • stress
  • endurance exercise
  • weight loss

More persistent irregularity may be a sign of an underlying condition.

The following sections look at some of the potential causes for irregular periods in more detail.

During puberty, the body undergoes significant changes. It can take several years for the hormones that regulate periods to fall into a reliable pattern. During this time, it is common to have irregular periods.

Oligomenorrhea can also occur after childbirth and while breastfeeding until the hormones return to normal after having a baby.

Breastfeeding, especially exclusive and frequent breastfeeding, can suppress ovulation, causing a person’s periods to stop. Doctors call this lactational amenorrhea.

Periods also become irregular during perimenopause, which is the first stage of menopause. During this time, hormone levels begin to fall. Periods may get further and further apart until a person stops having them entirely.

Learn about premenopause and perimenopause here.

Hormonal birth control works by stopping ovulation. This means a person does not have a true period while they are using it. Instead, some people have no period at all, while others will have withdrawal bleeds that can seem similar to a period.

When a person first starts the pill, patch, implant, or hormonal intrauterine device (IUD), they may experience irregular bleeding during the first few months. This may become more regular as time goes on or stop entirely.

Similarly, when a person stops using hormonal birth control, this can also lead to irregular periods. It takes time for the body’s hormonal cycle to begin working as usual again.

Typically, people have a withdrawal bleed 2–4 weeks after stopping birth control pills. The next bleed is a period. It can take up to 3 months for the cycle to settle into a regular pattern.

People who had irregular periods before they began hormonal birth control may return to having an irregular cycle after they stop using it.

Irregular periods can sometimes indicate a health condition, such as:

Polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a condition where small, fluid-filled sacs, known as cysts, develop in the ovaries. PCOS causes high testosterone levels, which can prevent or delay ovulation and a person’s period.

The other symptoms of PCOS include:

  • acne
  • excessive hair growth
  • insulin resistance that may affect weight
  • depression
  • trouble getting or staying pregnant

Learn more about the symptoms of PCOS here.

Eating disorders

Eating disorders, such as anorexia nervosa, bulimia nervosa, and binge eating disorder, can cause absent or irregular periods. This is more likely to occur if someone has experienced severe weight loss.

The signs of an eating disorder can include:

  • extreme restriction of food or calorie intake
  • cutting out whole food groups from the diet unnecessarily, such as carbohydrates
  • fasting, followed by binge eating
  • going to the bathroom immediately after meals
  • eating large amounts of food when not hungry

People who exercise excessively may also experience irregular periods. When people find it hard to stop exercising, it is known as compulsive exercise.

Learn the signs of an eating disorder here.

Endometriosis

Endometriosis is a condition in which cells that usually grow inside the uterus grow outside of it. These cells make up the uterine lining, which thickens and sheds with each menstrual cycle.

When the cells grow elsewhere, this cyclic thickening and shedding cause significant pain. Other symptoms include:

Learn more about endometriosis and infertility here.

Thyroid disease

The thyroid produces hormones that affect metabolism, heart rate, and other basic functions. It also helps control the timing of ovulation and periods.

People with hyperthyroidism produce too much thyroid hormone, while those with hypothyroidism do not produce enough.

Thyroid disease can make periods heavy or light and can make them more or less frequent. It can also cause ovulation to stop in some people.

Symptoms of hyperthyroidism include:

Symptoms of hypothyroidism include:

Thyroid disease is treatable. An underactive thyroid may require thyroid hormone, while radioactive iodine may help with hyperthyroidism. Some types of thyroid dysfunction require the removal of the thyroid.

Other conditions

Other health conditions associated with irregular periods include:

Irregular periods are usually not harmful. However, persistent or long-term irregularity may raise the risk of other conditions, such as:

  • Iron deficiency anemia: Blood contains iron. If periods are heavy or frequent, a person may lose enough blood to cause an iron deficiency.
  • Infertility: Irregular periods can result from anovulation, which is when the body does not release an egg. This can mean a person has difficulty getting pregnant.
  • Osteoporosis: Ovulation is a source of estrogen, which helps to keep the bones strong. If a person often does not ovulate, they may be at a higher risk for osteoporosis due to having less estrogen.
  • Cardiovascular disease: Similarly, a lack of estrogen can raise the risk of cardiovascular disease.
  • Endometrial hyperplasia: If a person has irregular periods for a long time without treatment, it may raise the risk for endometrial hyperplasia, which is when the uterus lining becomes unusually thick. This increases the risk of endometrial cancer.

Learn more about the importance of period symptoms here.

Having irregular periods from time to time is common and does not require treatment. Irregularity due to puberty, perimenopause, or contraception also does not typically require treatment.

However, someone may want to speak with a doctor if:

  • the irregularity is persistent and has no apparent cause
  • irregular periods could be related to a medication or health condition
  • irregular periods occur alongside other symptoms, such as pelvic pain
  • the person wants to get pregnant

If there is an underlying cause, a doctor will be able to diagnose it. Treatment will depend on what is causing the irregularity.

The potential treatment recommendations may include:

  • Hormone therapy: Birth control that contains the hormones estrogen and progesterone can help raise hormone levels, which can counteract the effects of not ovulating. It can also make bleeds regular and easier to manage or reduce the symptoms of conditions such as PCOS, which may improve quality of life.
  • Reaching a moderate weight: Both a lack of body fat and having excess body fat can impact menstruation. For those with PCOS who have higher body weight, maintaining a healthy weight can lower insulin levels. This leads to lower testosterone levels and an increased chance of ovulating.
  • Nutritional therapy: If a person wants to lose or gain weight or has an underlying condition that affects their nutrition, they may benefit from help from a dietitian. They can help a person understand the type of diet that will help with their unique circumstances and support hormone health.
  • Mental health treatment: If irregular periods are related to stress, anxiety, depression, or an eating disorder, a doctor may recommend psychological support. For many, this usually involves talk therapy with a psychologist. A multidisciplinary team will help with regular therapy, nutritional counseling, and support groups for those with eating disorders. People with severe underweight may need treatment in the hospital.
  • Additional medications: Depending on the underlying cause, people with irregular periods may benefit from certain medications. For example, a doctor may prescribe metformin for people with PCOS. This is an insulin-lowering oral drug for type 2 diabetes, which can help ensure ovulation and regular periods.

Learn whether home remedies can help regulate periods here.

Irregular periods can sometimes make it more difficult to get pregnant, as the times a person is ovulating may also be irregular. People who skip periods may also have months where they do not ovulate.

However, this does not mean that pregnancy is impossible. Tracking when someone is ovulating can help. Try:

  • Tracking periods: Mark any periods on a calendar, and look for patterns. Period tracking apps can help with pinpointing the time of likely ovulation. Ovulation almost always occurs about 2 weeks before a person’s period. However, the length of time between the start of the period and the next time a person ovulates can vary.
  • Monitoring cervical mucus: As ovulation approaches, the cervical mucus will be more plentiful, slippery, clear, and stretchy.
  • Measuring body temperature: Use a thermometer to measure body temperature first thing each morning and note when it spikes. This can indicate that someone has ovulated.
  • Using ovulation predictor kits: These products test for a surge in luteinizing hormone, which suggests ovulation is imminent. A person has likely ovulated if there is a prolonged increase in morning body temperature after a positive ovulation test.

If these methods do not help, speak with a fertility doctor about irregular periods. They will be able to provide advice on what to do next.

Learn more about irregular periods and pregnancy here.

Irregular periods and occasional variations in cycle length are normal. However, if a person regularly has very short or long cycles, something may be affecting their menstrual cycle.

Temporary causes for irregularity can include stress, natural hormonal changes, and starting or stopping birth control.

Certain medications and health conditions can also cause irregular periods. If this is the case, a doctor will be able to diagnose it and provide treatment recommendations.

People with irregular periods who want to get pregnant may benefit from tracking when they ovulate or speaking with a fertility specialist.