Is It Normal To Miss A Period?

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Ask Ella
Ask Ella

Your monthly gift, Aunt Flo, the crimson wave, shark week… Whatever you call it, your period is a regular (but sometimes unwelcome) visitor who lets you know your menstrual cycle is running smoothly.

Once in a while, however, you might look at the calendar and realise that Aunt Flo is running a bit late. Everyone’s cycle is different, and a missed period here and there isn’t necessarily something to worry about, but you still want to know what’s going on.

We spoke to Ella Craddock, the senior education and wellbeing co-ordinator for Brook, to find out all the reasons why you might have missed a period.

What health factors can make you miss your period?

Skipping your period can sometimes point to pregnancy, but that’s not the only reason Aunt Flo isn’t coming to visit.

“There are a number of reasons why your periods can stop,” says Ella, “the most common reasons are pregnancy, stress, sudden weight loss, being overweight or obese, extreme over-exercising , contraception choices, reaching the menopause, polycystic ovary syndrome (PCOS).”

Skipping your period could also be because of a medical condition. “Heart disease, uncontrolled diabetes, an overactive thyroid, or premature menopause,” says Ella, “everyone is different and so are their cycles; it’s important to speak with a doctor if you’re worried.”

Let’s take a closer look at some of those reasons you might miss your period…


Even if you didn’t have unprotected sex, no contraception is 100% effective. If you’re sexually active and your period is more than a week late, there is a chance you could be pregnant.

You can take a home pregnancy test from the first day of a missed period, but if you’re not sure when your next period is due you should take the test at least 21 days after you last had sex.

If you’ve only just started menstruating

Everyone’s cycle can vary and this is especially true of young people who have only just started to get their period.

It can take a little while for your body to get into the swing of things when you first start menstruating and that can mean your periods are irregular.

“You don’t need to get medical advice if you have always had slightly irregular periods or only just started your periods,” says Ella.

Contraceptive pill

Most contraceptive pills contains hormones which prevent ovulation. so when you go on the contraceptive pill you may notice some changes to your menstrual cycle.

Depending on which pill you’re on, you may find that your period is shorter, lighter, more regular, or that it may stop altogether.

If you come off the contraceptive pill, your body will need to adjust and this can take a bit of time. As a result, you may miss a few periods before your cycle becomes consistent again.


Stress alters the production of gonadotrophin which can interfere with ovulation and regular menstruation.

“For some people stress can impact their menstrual cycles. Their menstrual cycle can become longer or shorter, periods may stop altogether, or they might become more painful,” says Ella.

“Try to avoid becoming stressed by making sure you have time to relax,” she continues, “regular exercise, such as running, swimming and yoga, can help you relax. Breathing exercises can also help. But we’re all unique, so find something that works for you.”

Sudden weight loss

Sudden weight loss or being underweight can interrupt your menstrual cycle. When you’re underweight, your body may lack the fats and nutrients needed to produce hormones.

This can interfere with your menstrual cycle, stop ovulation and cause you to miss your period. Under-eating or over-exercising can have a similar effect.

Missing your period three months in a row due to extreme weight loss is called amenorrhea. If you suspect this is the cause of your missed periods, you should speak to your doctor.

Being overweight

Just as low body weight can affect your period, being overweight or obese can influence oestrogen and progesterone in your body and interrupt your menstrual cycle.

If you’re overweight your body may produce more oestrogen than usual which can affect how often you have your period, or stop it all together. If you have missed your period more than three months in a row, and think it could be due to your weight, you should speak to your doctor.


PCOS stands for polycystic ovary syndrome, a condition that affects around one in five women in the UK.¹

It is a hormonal imbalance which can cause your ovaries to become enlarged. As a result of this, ovulation doesn’t always happen. Irregular or missed periods are a very common symptom of PCOS.

Thyroid problems

Your thyroid is a gland that produces the hormones that control your body’s metabolism. An overactive or underactive thyroid can affect the levels of hormones needed for ovulation and can result in a late or missed period.

“People with vulvas are more likely than those without to have thyroid disease,” says Ella, “one in eight of whom will develop thyroid problems during her lifetime. In people with menstrual cycles, thyroid diseases can cause problems with your menstrual period.”

“Your thyroid helps control your menstrual cycle,” she continues, “too much or too little thyroid hormone can make your periods very light, heavy, or irregular. Thyroid disease also can cause your periods to stop for several months or longer, a condition called amenorrhea.”

“If your body’s immune system causes thyroid disease, other glands, including your ovaries, may be involved. This can lead to early menopause (before age 40).”

Changes in schedule

Sometimes a change in your schedule can mess up your body clock, which can make your period fairly unpredictable. An erratic schedule, and sometimes even jet lag can cause your period to be later than you might expect.

“Menstrual cycles are impacted by the release of hormones, so sleep pattern changes that are out of the ordinary like travelling between time zones and getting jet-lagged can impact the menstrual cycle,” says Ellen.

“It may mean your cycle changes in length, are skipped or are heavier/lighter than usual,” she continues, “it’s a good idea to take period products with you on these journeys though, your cycles should settle back to normal within a cycle or two,” she continues.

Can the morning after pill make your period late?

Most people will still have their normal period others may find that their period is a few days later than usual after taking emergency contraception.

“Emergency Contraception is the official name for the ‘morning after pill’, as they work longer than just the morning after,” says Ella, “there are two types of emergency contraception pill which can affect the menstrual cycle differently.”

ellaOne contains ulipristal acetate, which can work by delaying ovulation so no egg is released and therefore the sperm has nothing to fertilise. ellaOne can be taken up to five days after unprotected sex and is the most effective morning after pill*

Levonorgestrel contains progesterone, the synthetic hormone found in some birth control pills, and can also work by delaying ovulation. Levongestrel can be taken up to three days after unprotected sex.

Is the morning after pill 100% effective?

Please note that emergency contraception is not 100% effective. If your period is more than seven days late, is unusually light or heavy or if you are experiencing any possible symptoms of pregnancy (such as nausea) then we advise you take a pregnancy test and/or consult your GP.

Like all medications, the morning after pill can cause side effects in some people. Please note that many people experience no side effects at all and if they do they tend to be mild. Learn more about the side effects of the morning after pill here.

“If the morning after pill makes you vomit within three hours, you need to contact your doctor or pharmacist, as you may need to take another one,” says Ella.

Can your menstrual cycle change?

“Your periods can change – for example, they may last longer or get lighter,” says Ella, “this doesn’t necessarily mean there’s a problem, but it does need to be investigated if it has been happening for several cycles. In fact some slight variation from cycle to cycle is very common.”


  • You should see your GP if

    • Your periods suddenly become irregular and you're under 45
    • You have periods more often than every 21 days
    • Your periods last longer than 7 days
    • Your periods are very heavy and/or very painful
    • There's a big difference (at least 20 days) between your shortest and longest menstrual cycle
    • You have irregular periods and you're struggling to get pregnant

There might not be anything wrong, but it’s a good idea to get checked out to see what the cause might be. Remember cycle length is very likely to change slightly over the course of a lifetime, or from cycle to cycle.”

ellaOne® 30mg film-coated tablet contains ulipristal acetate and is indicated for emergency contraception within 120 hours (5 days) of unprotected sex or contraceptive failure. Always read the label.