# What Causes Irregular Periods?

March 16, 2023

The average [menstrual cycle](/content/blog/4-stages-of-the-menstrual-cycle/index.html) usually lasts for **28 days**, but it’s not uncommon for it to be a bit longer or shorter than that.

After puberty, many menstruators tend to experience a regular menstrual cycle, meaning there’s a similar length of time between periods. However, it’s normal for your cycle to vary by a few days every time.

According to the [American Academy of Family Physicians](https://www.aafp.org/pubs/afp/issues/2012/0101/p35.html), **9-14%** of menstruators have irregular periods from the time they get their first period to the start of menopause.

For various reasons, you may have irregular periods, so let’s dive into some of the most common explanations.

## 1. Increase in Stress

Did you know [stress hormones](https://www.pennmedicine.org/updates/blogs/womens-health/2020/november/irregular-periods-why-is-my-period-late) can directly impact your menstrual cycle? Prolonged stress can cause you to have irregular periods or, in some cases, to skip your period entirely.

## 2. Medical Conditions

Some health conditions are connected to missed or irregular periods. They include:

- Endometriosis
- Pelvic inflammatory disease
- Bleeding disorders
- Uterine or ovarian cancer
- Thyroid or pituitary gland disorders

## 3. Certain Medications

Specific medications can cause irregular periods. [Some medications](https://my.clevelandclinic.org/health/diseases/14633-abnormal-menstruation-periods) that may cause your period to be irregular include the following:

- Birth control pills, implants or injections
- Steroids
- Blood thinners
- Anti-epileptic drugs (AEDs)

## 4. Hormonal Imbalances

Several hormones play a huge role in your menstrual cycle. Because of this, [an imbalance](https://my.clevelandclinic.org/health/diseases/22673-hormonal-imbalance#:~:text=Irregular%20menstruation%20(periods)%3A%20Several,syndrome%20(PCOS)%20and%20amenorrhea.) in one or multiple of those hormones can result in irregular periods. Certain hormone-related conditions that can cause irregular periods include [amenorrhea](https://www.mayoclinic.org/diseases-conditions/amenorrhea/symptoms-causes/syc-20369299#:~:text=Amenorrhea%20(uh%2Dmen%2Do,a%20period%20by%20age%2015.) and [polycystic ovary syndrome (PCOS)](https://www.hopkinsmedicine.org/health/conditions-and-diseases/polycystic-ovary-syndrome-pcos#:~:text=PCOS%20is%20a%20very%20common,%2C%20infertility%2C%20and%20weight%20gain.).

## 5. Significant Weight Loss or Gain

Gaining or losing a significant [amount](https://www.everydayhealth.com/pms/weight-and-your-cycle.aspx) of weight can impact the production of your hormones (specifically estrogen), causing irregular periods.

## **When to See a Doctor**

You don’t need to seek out medical advice if you’ve always had slightly irregular periods.

But you should [see a doctor](https://www.nhs.uk/conditions/irregular-periods/) if…

- Your periods last longer than 7 days
- You have periods more often than every 21 days
- You have periods less often than every 35 days

_Sources: The American Academy of Family Physicians, Penn Medicine, Cleveland Clinic, Everyday Health & the NHS_

**Disclaimer:**  
[Aunt Flow](/content/site-root.html) does not provide medical advice. This content is for informational purposes only. No material on this site is intended to serve as a substitute for professional medical advice, diagnosis or treatment. Please consult your doctor or a qualified health professional with any questions you may have.