5 causes of missing periods

Missing periods

In this article, we cover five common reasons for missing periods, besides pregnancy.

Key Takeaways

  • Missing periods are common but not normal.
  • When you first start your menstrual cycle the first few years are likely to be irregular and this is normal. 
  • A normal cycle length is anywhere between 21 and 35 days and some variation is considered normal. 
  • If you are missing a period then pregnancy must be ruled out first.
  • Other causes of missing periods include PCOS, stress, undereating, perimenopause and thyroid imbalances.


First of all let’s ask a very frequently asked question: ‘are missing periods normal?’. Well to put it bluntly it may be common, but it is not ‘normal’. Therefore it is important to explore what might be going on for you and why. 

What does a normal cycle look like?

A normal cycle length is anywhere between 21 and 35 days. Interestingly only around 10-15% of women actually have a 28 day cycle.

A regular cycle is considered to be consistently the same length every month, give or take a couple of days. Natural fluctuations in a cycle are normal, so if your cycle is 31 days one month, and 35 days the next month, that’s still considered a regular cycle. 

The general rule is that the length of your menstrual cycle can vary up to 8 days in a year. This means one cycle may be 30 days, another 28 and another 35. This would mean there was a variation of 7 days (between the shortest 28 and longest 35). 

What about in adolescence?

When you first start your menstrual cycle, the first few years are likely to be irregular and this is normal. Your periods may also be heavier during this time as well. 


If you are missing a period then pregnancy must be ruled out first and foremost. 

This is important to rule out even if you are on birth control such as the oral contraceptive pill or IUD. 

Very rarely there may be ectopic pregnancies or pregnancies that may be missed. Ectopic pregnancies are pregnancies that are outside of the womb, for example in a fallopian tube. Sometimes these pregnancies do not even show a positive pregnancy test, therefore if you have missing periods it is always important to rule out pregnancy with your healthcare provider. Other signs of an ectopic pregnancy are pain, dizziness and nausea. 

5 other causes of missing periods

1. PCOS (Polycystic Ovarian Syndrome)

A common cause of missing or irregular periods is PCOS (polycystic ovarian syndrome). Those with PCOS often experience missing or irregular periods. Other symptoms of PCOS often include hair loss, excess hair growth on the body, acne and weight gain. There are four types of PCOS to be aware of:

  1. Insulin resistant PCOS 
  2. Inflammatory PCOS 
  3. Post-pill PCOS 
  4. Adrenal PCOS 

Read more about the four types of PCOS.

Typically insulin resistant PCOS (the most common type of PCOS) causes excess androgens (male hormones), which in turn can inhibit ovulation and cause irregular periods. 

It is very important if you suspect you have PCOS to discover the root cause and work with a practitioner to bring your hormones back into balance. We usually recommend the Advanced Hormone Test for women with PCOS as this looks at not only your sex hormones and their metabolites, but also adrenal hormones, nutrients and neurotransmitters. Once we have your results, our practitioners can put in place personalised recommendations for you to balance your hormones.

Symptoms of PCOS

2. Stress

Stress is one of the most common causes of a missing or irregular period. When the body and mind is under stress, the body prioritises survival instead of sexual reproduction. Therefore emphasis moves towards producing and regulating cortisol and adrenaline (our stress hormones) over estrogen and progesterone (our sex hormones).  

Some types of stress that can disrupt the menstrual cycle include:

  • Weight changes including both gaining weight and losing weight 
  • Traveling 
  • Illness
  • Changing schedules or jet lag
  • Mental stress like a stressful deadline at work 
  • Emotional stress, for example a stressful relationships 
  • Physical stress, such as over exercising and not getting enough sleep

Stress can disrupt the communication pathway from your brain to your ovaries, and interfere with the production of LH (luteinising hormone) and FSH (follicle stimulating hormone) from the pituitary gland. These hormones LH and FSH help to regulate your menstrual cycle, promoting healthy and regular ovulation and bleeding. When these are disrupted due to stress it can cause irregular and missing periods. 

Stress and the menstrual cycle

3. Weight changes and hypothalamic amenorrhea

As mentioned under ‘stress’, one of the biggest causes of a missing period can be weight changes. This includes both weight loss and gain. Let’s look more closely at weight loss. 

Weight loss (due to under eating or over exercising) can lead to something called hypothalamic amenorrhea. In fact you don’t even need to lose weight for hypothalamic amenorrhea to occur. 

Hypothalamic amenorrhea is defined as a missing period due to a problem with the hypothalamus. The hypothalamus is a control centre in the brain and it instructs the pituitary gland to release hormones that in turn regulate your sex hormones. Under eating or over exercising or other types of stress can disrupt the hypothalamus (as well as other parts of the body such as the thyroid) and lead to a missing period.

4. Perimenopause

If you are in your late 30’s or in your 40’s and experiencing new symptoms such as the following, then you are likely to be in perimenopause:

  • Heavy and/or longer periods
  • Shorter cycles – 25 days or less
  • New sore or swollen breasts
  • Mid-sleep waking
  • Increased period pain
  • Night sweats, particularly premenstrually
  • New or increased migraine headaches
  • New or increased premenstrual mood swings
  • Weight gain without changes in exercise or eating

You can read more about the signs and symptoms of perimenopause here.

Perimenopause is a time of fluctuating hormones, and changing cycles and typically happens across four stages. Initially cycles may be closer together at 21-25 days, but eventually you may begin to experience longer cycles of 45-60 days. Therefore if your period is late or missing, you may in fact be in perimenopause where cycle changes are a natural hallmark of this time. 

Signs & Symptoms of Perimenopause

5. Thyroid imbalances

The thyroid is a commonly overlooked gland in hormone health. It is a butterfly shaped gland at the base of your throat that is responsible for regulating your metabolism, heart rate and digestion (and your hormones!). 

The thyroid must always be looked at when your period is missing as it is a common culprit in irregular and missing periods. The thyroid is impacted by stress, environmental toxins, infections, pregnancy, nutrient status and more. 

You can read more about signs and symptoms of thyroid imbalances here.

So what might be happening with your thyroid to cause a missing period? The thyroid helps to regulate your sex hormones, and the thyroid is also in constant communication with your brain and ovaries too. If the thyroid is under active it can cause an increase in prolactin which can inhibit ovulation and cause missing and irregular periods. If the thyroid is overactive it can increase something called SHBG (sex hormone binding globulin) which regulates how much testosterone and estrogen is available in the body, when this is out of balance it can cause missing and irregular periods. 

Therefore the thyroid must always be tested in the event of a missing period, as even a small imbalance can have big impacts on the menstrual cycle. We always recommend asking for a a full thyroid blood panel from your doctor.

What to do about missing periods

Pregnancy, PCOS, stress, weight changes, thyroid imbalance and perimenopause are just some of the common causes of a missing period. If you are struggling with irregular or missing periods it is important to investigate why. 

First of all, test don’t guess! Testing your hormones and nutrients is crucial to assess what may be underlying your irregular or missing periods. We typically recommend the FUTURE WOMAN Advanced Hormone Test to gain a comprehensive picture of what’s going on with your hormones, as this looks at sex hormones and their metabolites but also adrenal hormones too. 

Each test comes with a report full of personalised, targeted recommendations to balance your hormones and help restore your missing periods.


  • Comprehensive sex and adrenal hormone and hormone metabolites test
  • Free return postage to our partner lab
  • Expert-reviewed report with your results
  • 5 personalised supplement, diet and lifestyle tips


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Kakuno, Y., Amino, N., Kanoh, M., Kawai, M., Fujiwara, M., Kimura, M., Kamitani, A., Saya, K., Shakuta, R., Nitta, S., Hayashida, Y., Kudo, T., Kubota, S., & Miyauchi, A. (2010). Menstrual disturbances in various thyroid diseases. Endocrine journal, 57(12), 1017–1022. https://doi.org/10.1507/endocrj.k10e-216

Koutras D. A. (1997). Disturbances of menstruation in thyroid disease. Annals of the New York Academy of Sciences, 816, 280–284. https://doi.org/10.1111/j.1749-6632.1997.tb52152.x

Ryterska, K., Kordek, A., & Załęska, P. (2021). Has Menstruation Disappeared? Functional Hypothalamic Amenorrhea-What Is This Story about?. Nutrients, 13(8), 2827. https://doi.org/10.3390/nu13082827

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