Why Is My Period Irregular?

You have an irregular period if it is shorter or longer than average or if you experience heavy or light bleeding, severe premenstrual syndrome (PMS), or pain during mensuration.

An average menstrual cycle occurs between 21 to 35 days and lasts about two to seven days. Typically about 1 to 6 tablespoons of blood is lost per period. Anything outside of that is considered irregular.

Lifestyle factors can lead to irregular periods, such as stress, obesity, new birth control, and smoking. More serious conditions can also cause abnormal menstruation, like endometriosis, pelvic inflammatory disease, and polycystic ovary syndrome (PCOS).

This article discusses the symptoms, causes, and treatments for irregular periods.

An image of a woman marking a calendar

Yusuke Ide / Getty Images

Symptoms of New Irregular Periods

Irregular periods vary from person to person. You may have had an irregular period all your life or have noticed new, concerning symptoms. Your period may be irregular if:

  • The time between your periods is shorter than 21 days or longer than 35 days.
  • You bleed for more than seven days.
  • Your period is heavy (changing a pad or tampon every hour).
  • Your period is light (bleeding less than two days).
  • You spot between periods.
  • You have not had a period for three to six months (outside of pregnancy).
  • Your cycle changes by more than 20 days each month.
  • Your periods are painful and interfere with daily life.
  • You feel pelvic discomfort.

You don't have to have all symptoms for your period to be considered irregular. However, if you're experiencing one or more symptoms, closely track your period cycles using an app or journal and schedule a visit with a healthcare provider.

Irregular periods happen. They should not cause immediate panic, but they should be taken seriously. If you've suddenly started to experience symptoms of irregular periods, contact a healthcare provider. Seek emergency medical care if you experience a very heavy period, feel pain in your chest, are lightheaded or dizzy, or are short of breath.

How Long Is It Normal to Have Irregular Periods?

Sometimes it can take a few months to notice irregular period symptoms, especially if they are not immediate or painful. That's why tracking your cycle is so important.

Discuss painful or immediate changes with a healthcare provider for a thorough evaluation and further treatment if needed.

Common Causes of Irregular Periods

It's common to experience irregular periods throughout your reproductive years, and many factors can cause them, such as lifestyle factors and natural reproductive cycles.

Some natural reproductive cycles causes include:

  • Menarche: Adolescents between 10 and 16 may have irregular periods for the first few years of menstruation.
  • Pregnancy: Those who choose to breastfeed after childbirth may experience absent or irregular periods for a few months to a year.
  • Perimenopause: Individuals in their late 30s to early 50s may experience irregular periods as a symptom of perimenopause.

Lifestyle factors and daily habits that can result in abnormal menstruation include:

  • Excessive exercise
  • Rapid weight changes
  • Obesity
  • Stress
  • Smoking
  • Birth control
  • Poor diet or nutrition
  • Low weight or body mass index

Underlying medical conditions could be causing irregularities, such as:

What Medications Can Cause Irregular Periods?

Some common medications can cause irregular periods, such as:

Tests to Diagnose The Cause of Irregular Periods

Based on your symptoms, a healthcare provider may recommend tests to help diagnose the cause of your irregular periods. These may include:

  • Pelvic exam
  • Blood test: Heavy or prolonged periods can lead to anemia, so they might want to check your iron levels or check for hormone levels and pregnancy
  • Pelvic ultrasound: Helps assess the reproductive organs and check for uterine fibroids, polyps, or ovarian cysts

Treatment Options for Irregular Periods

A healthcare provider will set up a treatment plan according to the underlying cause of your symptoms. A few treatment options may include:

  • Hormonal birth control can be prescribed to treat heavy bleeding caused by endometriosis, fibroids, and PCOS.
  • Gonadotropin-releasing hormone agonists (GnRH) can help reduce uterine fibroids' size and reregulate menstruation.
  • OTC nonsteroidal anti-inflammatory drugs (NSAIDs) like Advil (ibuprofen) or Aleve (naproxen) may be used to help with painful periods.

Eating a healthy, balanced diet, exercising moderately, managing stress, sleeping well, and adhering to routine healthcare visits can also help regulate irregular periods.

When to See a Healthcare Provider

Schedule a visit with a healthcare provider when you notice significant or surprising changes in your period, if you missed the last three periods, or if you're over 15 and have not started menstruating.

People approaching menopause may be correct to assume irregularities are normal reproductive fluctuations, but it's better to be safe, as there are more serious reasons to miss periods before menopause.


Irregular periods vary from person to person. Symptoms may include heavy or light bleeding, early or late periods, and more. Pregnancy, lifestyle factors, age, medication, or more serious conditions, such as endometriosis and PCOS, can cause menstrual irregularities. Irregular periods should not cause immediate panic but should be taken seriously. Track any changes in menstruation and schedule an appointment with a healthcare provider.

7 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Planned Parenthood. How do I know if my mensuration is normal?

  2. Bae J, Park S, Kwon JW. Factors associated with menstrual cycle irregularity and menopause. BMC Womens Health. 2018;18(1):36. doi:10.1186/s12905-018-0528-x

  3. Eunice Kennedy Shriver. National Institute of Child Health and Human Development. What causes menstrual irregularities?

  4. American College of Obstetricians and Gynecologists. Heavy and abnormal periods.

  5. American College of Obstetricians and Gynecologists. Abnormal uterine bleeding.

  6. Lacroix AE, Gondal H, Shumway KR, Langaker MD. Physiology, menarche. In: StatPearls. StatPearls Publishing; 2023.

  7. Penn Medicine. Irregular periods: why is my period late?