11 Reasons for a Late Period (Besides Being Pregnant!)

Picture this: you’re constantly thinking about crisps, your boobs are sore, you’re feeling bloated and everything feels like it’s one inch away from making you cry. Your period might not be your idea of a good time, but this regular monthly visitor usually lets you know that your menstrual cycle is running smoothly.

Once in a while, however, you might look at the calendar and realise that your period is running a bit late. Everyone’s cycle is different and missing a period isn’t necessarily a cause for alarm, but you still want to know what’s going on. 

So why might you miss a period if you’re not pregnant? We spoke to Ella Craddock, the senior education and wellbeing co-ordinator for Brook, and  Dr. Martha Tara Lee*, a Relationship Counselor & Clinical Sexologist, to find out.

Skipping your period can sometimes point to pregnancy, but that’s not the only possible cause.

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

As well as physical factors, anything from your mood to changes in your sleep pattern can affect your cycle. “The menstrual cycle offers insights into our body’s language, where missed periods may speak volumes about our physical, emotional, and environmental landscape.” says Dr. Martha Tara Lee. 

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

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.

Menopause is when your periods stop altogether due to lower hormone levels. It usually happens between the ages of 45-55, but it can happen earlier. Menopause is a part of life that everyone who gets periods will go through at some point. 

It’s important to go to a doctor if you suspect menopause, so you can confirm it and make sure you have everything you need to manage the transition as easily as possible.

Contraceptive pills contain synthetic versions of naturally occurring hormones which help prevent ovulation, which means no egg is released and so any sperm which gets inside the body has nothing to fuse with. 

“Changes in birth control methods, such as starting or stopping hormonal contraceptives like the pill, patch, or injection, can affect menstrual cycles,” says Dr Lee. “It may take time for the body to adjust to new contraceptive methods, leading to temporary changes in menstruation patterns.”

Depending on which pill you’re on and how you react to it, you may find that your period becomes shorter, lighter, more regular, heavier, or they 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, whether emotional or physical, can disrupt the delicate hormonal balance necessary for regular menstruation,” says Dr Lee. “High levels of stress trigger the release of cortisol, a hormone that can interfere with the production of reproductive hormones, leading to irregular or even missed periods.”

Stress can also alter the production of gonadotropin-releasing hormone, which stimulates your production of oestrogen and progesterone. Altering this can interfere with ovulation and regular menstruation.

“Try to avoid becoming stressed by making sure you have time to relax,” Ella adds, “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 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.

 “Extreme changes in diet, such as rapid weight loss or excessive calorie restriction, can disrupt hormone levels and affect menstrual regularity,” says Dr Lee. “Additionally, deficiencies in essential nutrients like iron or vitamin B12 can impact reproductive health.”

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

Whether you’re a female athlete or you’ve ramped up that exercise regime, you might find that you stop getting your period. “Intense or excessive physical activity, particularly endurance sports or rigorous training regimens, can affect hormone levels and disrupt menstrual cycles,” says Dr Lee. “Athletes, dancers, and individuals with high levels of physical activity may experience irregular periods or amenorrhea (absence of menstruation).”

Exercise in itself doesn’t stop you having your period, but what can happen is that you’re using more energy than you’re consuming, which means you have a lack of available energy to run some of your ‘inessential’ bodily processes, which can include ovulation. If you’ve noticed that you’re not getting a regular period when you used to, or if your periods have stopped altogether, you should speak to your doctor for advice. They may recommend you cut back on the exercise for a while or up your calorie intake to make sure your body is getting the energy it needs.

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 altogether. 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. They may refer you to a dietitian who can help you lose weight safely.

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

“Certain medical conditions, such as PCOS thyroid disorders, or hormonal imbalances, can cause menstrual irregularities or missed periods,” says Dr Lee. It’s essential to consider underlying health issues when evaluating the reasons for a missed period.”

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 irregular periods.

“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.” 

If your periods are irregular or have stopped and you’re concerned that there may be an underlying medical reason, speak to your doctor for advice. “In addition to the medical conditions mentioned earlier, other health issues such as diabetes and eating disorders may contribute to menstrual irregularities,” says Dr Lee.  

Travel can impact our hormones, particularly cortisol (involved with stress) and (melatonin involved with sleep). 

“Changes in time zones, disruptions to routine, and physical exertion associated with travel can impact the body’s hormonal balance, leading to irregularities in menstrual cycles,” says  Dr Lee. “Jet lag and long flights may also contribute to menstrual disturbances.” In short, travel can affect the menstrual cycle because it can affect sleep and cause stress. 

Our mood and mental state can have a massive impact on our physical body. “Emotional factors, such as anxiety, depression, or emotional trauma, can affect menstrual cycles through their influence on stress hormones and the central nervous system,” says Dr Lee. “Addressing emotional well-being and managing stress levels are crucial aspects of maintaining menstrual health.”

Everyone is different, and that includes their menstrual cycles. The average length of a menstrual cycle is 28 days, but it can be as short as 21 days or as long as 35. Your cycle can also vary from month to month, and it’s normal for your period to be a few days early or a few days late every now and then.

“It’s essential to recognise that menstrual cycles can naturally vary in length and regularity from one individual to another,” says Dr Lee. “Some people may have consistently regular cycles, while others may experience occasional irregularities without any underlying health concerns.”

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 think you could be pregnant, we recommend taking a pregnancy test as soon as possible.

Most people will still have their normal period, others may find that their period is a few days earlier or 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 helps prevent pregnancy in the event of unprotected sex or contraception failure by delaying ovulation so no egg is released and therefore the sperm has nothing to fertilise. 

As ovulation may be delayed, your period may be up to seven days late.  ellaOne can be taken up to five days after unprotected sex and is 2.5x more effective than morning after pills containing levonorgestrel when taken within 24 hours.**

Please note that emergency contraception is not 100% effective. Morning after pills help delay ovulation, so if ovulation has already occurred then hormonal emergency contraception will not be 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 to take a pregnancy test and/or consult your GP.

Like all medications, the morning after pill can cause side effects in some people. “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.

“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.”

If you have any concerns about pregnancy, even if you’re experiencing symptoms not listed above, then we advise talking to a healthcare professional. There might not be anything wrong, but it’s a good idea to get checked out to see what the cause might be. 

*The people quoted in this article do not endorse any products or brands.

** Verify at: ellaone.co.uk/verify

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.

https://my.clevelandclinic.org/health/body/22525-gonadotropin-releasing-hormone 

https://www.nidirect.gov.uk/conditions/stopped-or-missed-periods 

https://www.nhs.uk/conditions/menopause/ 

https://health.clevelandclinic.org/is-it-normal-to-lose-your-period-because-of-exercise 

https://www.health.com/condition/menstruation/travel-affecting-period 

https://www.nhs.uk/conditions/vitamin-b12-or-folate-deficiency-anaemia/complications/ 

https://www.verywellhealth.com/heavy-menstrual-periods-iron-deficiency-anemia-5072751