Mother and Baby

21 reasons why your period may be late (if you're definitely not pregnant!)

Section: Skin & Hair
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As much as we hate periods and they quite often cause us pain and misery, it is sometimes nice to see mother nature doing is doing its job and your body is ticking along nicely. So when your menstrual cycle isn't regular or your period doesn't appear, it can be a bit worrying. 

Read more: The early signs of pregnancy

If you're trying for a baby, a missed period is likely to make you assume you've been successful. But what happens if you've done a pregnancy test and it is negative?

Perhaps you know you can't be pregnant because you've just had a baby and are wondering why your periods haven't gone back to normal.

If you have missed a period but you're definitely not pregnant, there are lots of other less obvious factors or medical reasons that might be causing your late period...

21 reasons why your period might be late:

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1) Miscalculation

Some people’s periods are regular as clockwork and they know exactly when they are due but if you’re less certain it may be down to a simple miscalculation. An average menstrual cycle is 28 days but this varies, with some women having shorter cycles and some longer. Your cycle length or regularity may also change as you age. Track your periods with an app to give you a bit more clarity.
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2) Birth control

Basically, all forms of hormonal contraceptives (the pill, IUD, implants, injections etc.) can mess up your cycle or general flow. If you have used these you might find you have an incredibly light flow or even stop getting a period completely.

For some women with bad periods, no longer having them is a godsend, but not if you are trying for a baby or you like to know exactly what’s going on. Even if you come off contraception it can take a while for your body to catch up and for your period to go back to normal.
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3) Medication

Certain prescriptions can affect your period. If you have been prescribed medication recently (antibiotics, antidepressants, steroids etc.) or a regular prescription has changed, this might be why your period is late.
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4) ​Recreational drugs

The use of recreational drugs can have an impact on your period. If you are trying for a baby, using illicit drugs can also contribute to fertility or ovulation issues and problems during pregnancy.

The NHS explains that illegal drugs ‘can have a potentially serious effect on your unborn baby’ and if you use them regularly ‘it’s best not to stop abruptly without first seeking medical advice.’
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5) Weight loss

Excessive or sudden weight loss can cause periods to stop. If you severely limit the calories you eat it can stop the production of hormones vital for ovulation. The general advice is to see your GP if your BMI is under 18.5 and you are concerned.
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6) Weight gain

On the other end of the spectrum if you gain weight quickly or are very overweight you may have issues with your period because of too much oestrogen. This excess of oestrogen can also stop the ovulation process. Generally, if you are concerned and have a BMI of 30 or more you should see your GP.
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7) Eating disorders

In the same way as weight loss, eating disorders such as Anorexia or Bulimia can lower oestrogen levels to drop preventing menstruation.
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8) Poor diet

There is a real theme building here. That what we eat and put into our bodies can have an impact on our menstrual cycle. If you eat a very poor and unhealthy diet or skip meals regularly this might be the cause. Healthy diet = healthy cycle. If you’re trying to get pregnant there are several foods you can eat to help you conceive.
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9) Excessive exercise

Exercising, in general, is great and can do wonders for your body. However, intense or excessive exercise puts our body through stress which can affect the hormones responsible for your period.

Professional athletes or dancers often have issues with their periods being disrupted. If you think that’s to blame, ease up on the gym. Try more gentle exercise such as walking, which can also give you a positive hormone boost just from getting outside!
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10) Just started having periods

If you’re a youngster and you’ve only just started your period they are often irregular or non-existent for extended periods. It takes time for your body to get used to the process of womanhood that you are going through, so don’t worry. Just be patient and your body will get into the right rhythm gradually.
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11) Sickness

Your body is even more clever than you think. If you’re really unwell, even with a cold or flu then your body might have decided to skip ovulation or delayed it for your own good. Your period may arrive late or not at all this month. If you have recovered from your illness then next month hopefully things will be back to normal.
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12) Stress

We already know that intense exercise puts our body under stress which can affect our period. So, it makes sense that general stress can do the same thing. Adrenaline and cortisol play havoc with the hypothalamus and your hormones.

Stress could be down to work, relationships, life changes or bereavement and your body will keep you in limbo, holding off on some of your bodily functions until the stress subsides.
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13) A change in schedule

The human body is very temperamental. If you have a change in your routine such as changing shifts at work, travelling or if you’re simply trialing getting up earlier, then this could play a part in stopping your periods. If your internal body clock has changed then your body needs time to get used to it. Once you settle into your new routine, your period should resume as normal.
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14) Having a baby

If you’ve had a baby recently then it will make your periods irregular or non-existent initially. Hormone levels do not go back to normal immediately after birth and the hormones which usually regulate our periods are less important during this busy time for your body. 
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15) Breastfeeding

If you are breastfeeding this is likely to mess with your periods. Both having a baby recently and breastfeeding have a hefty impact on our body’s hormones.
Breastfeeding mothers begin ovulation after birth much later. Prolactin, the hormone responsible for the secretion of milk suppresses the process of ovulation which means while a mother is breastfeeding, prolactin will remain in the body, affecting the ovulation process. Only once a successful ovulation cycle is completed will you start menstruating again.
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16) Hormone problems

Hormones control your menstrual cycle. Hence why in every reason we’ve given so far, hormones have a significant part to play. A change in your hormone levels, in general, will nearly always have an impact on your cycle.
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17) Thyroid problems

Your thyroid helps control your menstrual cycle so if you have had or think you may have thyroid issues then this could be affecting your periods. Women’s Health explains that if you have too much or too little thyroid hormone then this can make periods very light, heavy or irregular. Thyroid disease also causes Amenorrhea, a conditionwhere your periods stop for several months or more.
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18) Polycystic Ovary Syndrome

Polycystic Ovary Syndrome is a hormonal problem that affects about 10 million people in the world, according to the Polycystic Ovary Syndrome Awareness Association (PCOSAA).

People with PCOS typically have non-existent or irregular periods. It is a leading cause of female infertility and is responsible for a number of symptoms that can affect the body physically and emotionally. If you believe this might be the cause of your late period, it is advised you contact a doctor. 
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19) Chronic diseases

‘Girls with many diseases such as Crohn’s disease, celiac disease, cystic fibrosis, sickle disease, lupus, diabetes, and others may have irregular menstrual periods or amenorrhea because of low weight, stress, or a flare in their illness’ explains Young Women’s Health.
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20) Premature menopause

Early menopause happens when a woman’s periods stop before the age of 45. Premature menopause can be caused naturally by abnormalities, autoimmune diseases or infections. Premature menopause may also be brought on due to cancer treatments such as radiotherapy and chemotherapy or by a hysterectomy (an operation to remove the womb).

As well as irregular period other symptoms of early menopause can include:
  • hot flushes
  • vaginal dryness or discomfort during sex
  • difficulty sleeping
  • low mood or anxiety
  • reduced sex drive
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21) Menopause

The traditional menopause should occur in women of 45-55 years of age. The average age of menopause is 51. The ‘Menopause is the point when a woman’s body stops producing and releasing eggs. Doctors often define the menopause as when a woman has not had a period for 12 months or more’ says Wellbeing of Women, a charity dedicated to improving the health of women. The symptoms are the same as premature menopause.


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Catriona originally joined the team as an Editorial Assistant to work on the 2019 M&B Awards. As a Digital Writer, she has written and updated hundreds of articles on the site from medical explainers to celebs news and shopping galleries.

Catch her running along the Thames or eating her way around London's restaurants.


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