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Is your period irregular?

Is your period irregular?

Maybe you’re able to plan your vacation around your periods. Or maybe you carry extra tampons and pads in your purse, always prepared for the unexpected. Perhaps painful periods and heavy bleeding have greatly impacted your everyday life. No matter what your period is like, at some point you’ve likely wondered: “Is this normal?”

Here’s the thing about periods: No two are identical. And studies show that up to one-third of women will experience irregular bleeding in their lifetime.1 Understanding your menstrual cycle  and knowing how to identify and possibly find solutions for period problems can help you make informed decisions about conception and family planning. And that’s powerful.

So, what does having an “irregular period” mean?

An irregular period typically refers to timing, heaviness of flow and/or spotting. 

  • Timing can mean the length of your menstrual cycle and/or the length of your period. 
  • Heaviness of flow refers to how much you’re bleeding and/or any clots you may be experiencing. 
  • Spotting can happen between your periods and/or after certain activities, such as sex. 

Irregular periods are sometimes called abnormal periods, but they are much more normal than you may think. 


Just because your period isn’t on a perfect 28-day cycle doesn’t mean it’s irregular. In a recent study of more than 32,000 women, 25.3% of users described their cycle length as 28 days, but only 12.4% of users actually had a 28-day cycle. Most women (87%) had cycles ranging from 23 to 35 days, and 52% of women had cycles that varied in length by five days or more.2

A regular menstrual cycle can last anywhere from 24 to 38 days,3 with your period generally lasting three to seven days within that span of time. And if you’re a teenager, a regular cycle can last between 21 and 45 days, with a typical period lasting two to seven days.4 For adult women, be mindful of cycles that last longer than 38 days or are shorter than 24 days, and period lengths that vary by more than seven to nine days month to month.3

Heaviness of flow 

Maybe you’re going through tampons more often than you used to or you have to use pads with your tampons for extra protection. If so, you may be experiencing heavy menstrual bleeding, defined as bleeding that lasts more than seven days or is unusually heavy in volume.4 

That’s easier to figure out than you might think. If you’re regularly needing to change your tampon or pad every hour for several hours in a row, or if you pass clots bigger than the size of a quarter, your menstrual bleeding is heavier than normal.5 If this feels familiar, you’re not alone. According to the Centers for Disease Control and Prevention, heavy menstrual bleeding affects more than 10 million U.S. women — one in five — every year.6

Spotting between periods 

Bleeding or spotting between periods or after sex, while common, can also be a sign that something’s amiss. We’ll discuss that in more detail below. 

Why is my period irregular? When should I talk to my doctor?

Heavy bleeding during your period, bleeding or spotting between periods or after sex, and periods that are longer or shorter than usual are worth investigating with your healthcare provider. Talk to your doctor — they’ll be able to provide additional guidance on the symptoms you may be experiencing and what your next steps should be.

Potential problems of the uterus and ovaries 

  • Endometriosis, which is when the tissue that forms the lining of the uterus exists outside the uterus, can cause heavy and painful periods. This condition affects one in 10 women, typically in their 30s and 40s.7,8 (common)
  • Uterine fibroids develop as noncancerous growths from the muscle of the uterus. They can cause heavy and painful periods that last longer and are more frequent. Uterine fibroids can also cause bleeding between periods. 8,9 (common)
  • Endometrial polyps, also called uterine polyps, develop as noncancerous growths on the lining of the uterus. They can cause heavy and painful periods that occur irregularly. These polyps can also cause bleeding between periods and after menopause.8,10 (common)
  • Pelvic inflammatory disease (PID) is a bacterial infection of the reproductive organs, including the uterus, ovaries or fallopian tubes. More than 1 million U.S. women are diagnosed with PID each year. One of PID’s symptoms is irregular menstrual bleeding. Untreated, PID can cause infertility.11 (fairly common)
  • Adenomyosis, which is when tissue that typically lines the uterus starts growing inside the muscle wall of the uterus, can cause painful periods and heavy bleeding.8 (fairly common)
  • Endometrial cancer is most often diagnosed in women who are past menopause. For premenopausal women, this type of cancer can cause irregular bleeding, and bleeding and spotting between periods. If you are postmenopausal and you experience vaginal bleeding, it’s important that you see your doctor.8,12 (rare)

Hormone-related issues 

  • Polycystic Ovarian Syndrome (PCOS) is thought to be caused by a hormone imbalance, resulting in women with PCOS having elevated levels of LH (luteinizing hormone) throughout their cycle. PCOS can cause absent periods, periods that occur too frequently or infrequently and/or heavy periods. 8,13,14 (common)
  • Hypothyroidism, which occurs when you have an underactive thyroid gland, can cause more than usual menstrual bleeding. 8,15 (common)
  • During perimenopause, the years leading up to menopause, your cycles may become longer or shorter, and your flows may become heavier or lighter.13,16 (common)

Other conditions to investigate with your doctor 

  • An ectopic pregnancy happens when a fertilized egg grows outside the uterus. If you are pregnant or you’ve just found out you’re pregnant and you’re experiencing irregular vaginal bleeding, it’s important you contact your doctor right away.17 (rare)
  • Heavy bleeding often occurs during and around the time of a miscarriage. Sometimes this heavy bleeding can be mistaken for a heavy period. If there’s a chance you could be experiencing a miscarriage, talk to your doctor right away.18 (fairly common)
  • Breakthrough bleeding is common if you take hormonal birth control like pills, implants, IUDS, shots, rings or patches. Irregular spotting and bleeding typically happen in the first few months and then taper off.19 (fairly common)
  • Medications, including blood thinners, can sometimes cause heavy menstrual bleeding. If your period is different and you’ve recently changed or started a new medication, talk to your doctor — there could be a connection.8 (fairly common)
  • Bleeding disorders can cause irregular periods. Von Willebrand disease, the most common inherited bleeding disorder among U.S. women, is a common cause of heavy menstrual bleeding.8, 20, 21 (fairly common)
  • Extreme weight loss, weight gain or stress can affect your periods as well.13 (fairly common)

Irregular periods and pregnancy

Can irregular periods cause infertility? No. But sometimes the underlying cause can contribute to infertility, and irregular periods can make getting pregnant more difficult. In addition, irregular periods can make it difficult to track ovulation. Knowing when you ovulate — your fertility window — is key to knowing when (or when not) to have sex for pregnancy.

If you think your period may be considered clinically irregular, talk to your doctor. But keep in mind: It’s not uncommon, and you’re certainly not alone. By taking steps to better understand your menstrual cycle, you’ll feel empowered to make informed decisions about everything from the number of tampons you need to buy and vacation planning to conception and family planning. 




  1. Davis E, Sparzak PB, “Abnormal Uterine Bleeding,” updated February 10, 2021, StatPearls, https://www.ncbi.nlm.nih.gov/books/NBK532913/.
  2. Soumpasis, I., Grace, B., & Johnson, S., “Real-life insights on menstrual cycles and ovulation using big data,” Human reproduction open, 2020(2), hoaa011. https://doi.org/10.1093/hropen/hoaa011.
  3. “Abnormal Uterine Bleeding,” (2020, January) The American College of Obstetricians and Gynecologists. https://www.acog.org/womens-health/faqs/abnormal-uterine-bleeding.
  4. “Heavy and Abnormal Periods,” (2020, October) The American College of Obstetricians and Gynecologists, https://www.acog.org/womens-health/faqs/heavy-and-abnormal-periods.
  5. “Heavy Menstrual Bleeding,” (2021, May) The American College of Obstetricians and Gynecologists, https://www.acog.org/womens-health/faqs/heavy-menstrual-bleeding.
  6. “Bleeding Disorders in Women: Heavy Menstrual Bleeding,” (n.d.) Centers for Disease Control and Prevention, retrieved September 20, 2021 from https://www.cdc.gov/ncbddd/blooddisorders/women/menorrhagia.html.
  7. “Endometriosis,” (2021, February) The American College of Obstetricians and Gynecologists, https://www.acog.org/womens-health/faqs/endometriosis.
  8. “Heavy periods,” (2018, June 7) National Health Service, https://www.nhs.uk/conditions/heavy-periods/.
  9. “Uterine Fibroids,” (2020, June) The American College of Obstetricians and Gynecologists, https://www.acog.org/womens-health/faqs/uterine-fibroids. 
  10. “Endometrial polyps,” (2020, December 3) National Institutes of Health, U.S. National Library of Medicine, https://medlineplus.gov/ency/article/007636.htm.
  11. “Pelvic Inflammatory Disease (PID),” (2019, August) “The American College of Obstetricians and Gynecologists, https://www.acog.org/womens-health/faqs/pelvic-inflammatory-disease.
  12. “Endometrial Cancer,” (2019, February) The American College of Obstetricians and Gynecologists, https://www.acog.org/womens-health/faqs/endometrial-cancer.
  13. “Irregular Periods,” (2021, April 27) National Health Service, https://www.nhs.uk/conditions/irregular-periods/.
  14. “Polycystic Ovary Syndrome (PCOS),” (2020, June) The American College of Obstetricians and Gynecologists, https://www.acog.org/womens-health/faqs/polycystic-ovary-syndrome-pcos.
  15. “Thyroid disease,” (n.d.) Office on Women’s Health, U.S. Department of Health & Human Services, retrieved September 20, 2021, from https://www.womenshealth.gov/a-z-topics/thyroid-disease.
  16. “The Menopause Years,” (2020, July) The American College of Obstetricians and Gynecologists, https://www.acog.org/womens-health/faqs/the-menopause-years.
  17. “Ectopic Pregnancy,” (2018, February), The American College of Obstetricians and Gynecologists, https://www.acog.org/womens-health/faqs/ectopic-pregnancy.
  18. “Early Pregnancy Loss,” (2020, February) The American College of Obstetricians and Gynecologists, https://www.acog.org/womens-health/faqs/early-pregnancy-loss.
  19. “What You Should Know About Breakthrough Bleeding With Birth Control,” Dr. Valerie French, (2021, January) The American College of Obstetricians and Gynecologists, https://www.acog.org/womens-health/experts-and-stories/the-latest/what-you-should-know-about-breakthrough-bleeding-with-birth-control.
  20. “Management of Acute Abnormal Uterine Bleeding in Nonpregnant Reproductive-Aged Women,” Committee Opinion No. 557, April 2013, reaffirmed 2020, American College of Obstetricians and Gynecologists, https://www.acog.org/clinical/clinical-guidance/committee-opinion/articles/2013/04/management-of-acute-abnormal-uterine-bleeding-in-nonpregnant-reproductive-aged-women.
  21. “Von Willebrand Disease in Women,” Committee Opinion No. 580, December 2013, reaffirmed 2021, The American College of Obstetricians and Gynecologists, https://www.acog.org/clinical/clinical-guidance/committee-opinion/articles/2013/12/von-willebrand-disease-in-women.