How Long are Normal Menstrual Cycles?

How Long are Normal Menstrual Cycles?

Wondering if you have normal menstrual cycles, or if they are unusually short or long? In this post, we will explain the typical length range for a normal menstrual cycle and some factors that might impact the length of your cycles.

According to NHS in the UK, “The length of the menstrual cycle varies from woman to woman, but the average is to have periods every 28 days. Regular cycles that are longer or shorter than this, from 21 to 40 days, are normal.”

So, as long as your periods are within that general range as an adult, they are quite normal.

For young people, periods may be even longer initially. So, if you are reading this as a teen and your periods are more than 40 days, you may still be well within the normal range.

You also should know that some people’s menstrual cycles are more regular than others. One person might always have exactly the same length on almost every month, and another could have fairly wild fluctuations in length from month to month.

It is worth noting that the part of your period that happens before ovulation, called the “follicular phase,” is more likely to vary significantly in length than the phase which comes afterwards, known as the “luteal phase.”

This page quotes Sarah Babbs, Fertility Care Practitioner at Carmel Family Fertility Services in Carmel, Indiana, as explaining, “Each individual woman will only have slight variations in luteal phase length.” The site continues, “However, Babbs adds, there are exceptions. If you find that your luteal phase length is varying more widely than a day or two from month to month, your antennae should perk up. A wide luteal phase discrepancy is a good indicator of a hormonal problem.”


Here are some factors that could account for why some menstrual cycles are longer or shorter than others:

  • Taking hormones
  • Taking medications or supplements that influence hormone production
  • Stress
  • Smoking
  • How much one weighs
  • Certain underlying health conditions such as endometriosis or polycystic ovary syndrome (PCOS)
  • Pregnancy
  • Perimenopause

The occasional short or long cycle could just be due to stress or another lifestyle factor. And again, larger fluctuations are common for some people. As the years go by, you will get a better feel for what “normal” is for you. Just keep in mind that as you age, your “normal” can change.

If you do think that you have had one or more cycles that are abnormal for you, the safest thing to do is to contact your healthcare provider to check for underlying conditions and rule out anything serious.

This can also be worthwhile even if you are undergoing a perfectly normal life change like perimenopause, since this is a good point to get some information and advice for the months or years ahead of you.

Also, be aware that hormones can be complicated and confusing, even for specialists. For that reason, sometimes a doctor may not find an underlying condition, but you could still experience hormonal imbalances and resulting symptoms.

Managing those types of scenarios often involves a good deal of trial and error, not to mention patience. But it is worth taking the effort so you can enhance your menstrual health and live your best life.




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