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Irregular periods: Why it's late

10 Sep 2021 • 2 min read


Periods: half the population gets them, but how much do you really know about them?

Do you know exactly what they are, why they are usually regular, and what it can mean if they are irregular?

Here is the low-down.

What is a normal menstrual cycle?

It is good to know what is considered ‘normal’ for the period cycle, before examining whether or not your menstruation is irregular.

The menstrual cycle, period cycle or ovulation cycle, paves the way for bearing a child.

The cycle involves the vagina, uterus (also known as the womb), fallopian tubes (also known as the uterine tubes) and the ovaries.

In a normal, or regular cycle, female bodies release a hormone that makes the ovaries release an egg.

Concurrently, the hormone oestrogen (estrogen) is released to thicken the lining of the womb.

The egg travels along the fallopian tubes to the uterus. If it meets a sperm along the way, it might become fertilised, at which point the now-thick lining of the womb catches it.

Or, if the egg did not get fertilised, hormone levels drop, making the lining of the uterus dissolve.

This leaves the body as blood and is what we call a period.1

Most people who menstruate follow this ‘normal’ cycle, which tends to be very predictable.

Many women will know how often their period comes, how long it will last, and what size pad or tampon they will need to use on each day.

However, those with irregular periods probably cannot predict one or more of these things.

What are irregular periods?

Typically, irregular periods have one or more of the following characteristics:2

  • they are unpredictable, occurring either more frequently or infrequently than the normal range of cycle length (21-40 days)
  • they last longer than seven days
  • you cannot predict the flow of blood – whether it will be heavy or light.

People with irregular periods might become distressed by the lack of predictability.

A good way to take back some control over your irregular periods is by using a period tracking app, or an old fashioned diary.

Not only will this knowledge help you if you want to get your periods checked out by a doctor, but it might become vital information if you want to try to get pregnant.

Causes of irregular periods

According to the NHS, the top five causes of irregular periods are:3

  1. Puberty or the start of the menopause

Hormonal changes in adolescence as well as towards the end of your reproductive years can cause irregular periods.

  1. Pregnancy

Even during early pregnancy, some women may still experience irregular bleeding.

A good way to rule this out is with a pregnancy test.

  1. Some types of hormonal contraception

The contraceptive pill or intrauterine system (coil), for example, can both change your normal menstruation process.

  1. Extreme weight change, exercise or stress

Anything that puts a lot of strain on the body, such as losing significant weight or over-exercising, as well as stress, can cause its normal functions to play up.

  1. Some medical conditions

Common culprits include polycystic ovary syndrome and thyroid issues.

5 signs that your period is coming

Period symptoms are so common and ubiquitous among those who have periods they have been given a name: premenstrual syndrome, or PMS (formally referred to a premenstrual tension or PMT).

If you want to be more clued up to the changes your body goes through during normal period cycle, including the premenstrual symptoms you might experience, try downloading a period tracker app.

Period tracker apps are a helpful way to empower yourself and get to know your body better.

Not only can you keep track your period cycle, but they let you know your ovulation period if you want to get pregnant (or else avoid it!).

You can also log whether you have irregular periods.

Many period trackers will average out your cycle, so you can tell at a glance whether you have had a particularly short or long menstrual cycle.

Common signs of period starting

So how do you know if your period is on its way?

Here are some of the most common signs that you are about to start your period:4

  1. Mood changes

The cliché of the woman who is irrationally angry around the time of her period comes from this well-known PMS symptom!

PMS does not necessarily affect every woman but for those who do suffer mood changes before their period, they can be quite destabilizing.

The hormone changes that go on during your menstrual cycle can cause mood swings or mood changes.

These feelings might include anxiety, low mood, anger, or irritability.

Many people find that tracking their mood is where a period tracker can be really useful.

If you are able to spot a pattern where you are unusually sad or down, and that it happens to coincide with the start of your period, it means you will be better equipped to deal with it: knowledge is power!

  1. Cramps, aches and pains

Maybe it is your hormones making you crabby, but your mood change could also be due to discomfort or pain.

Whether you feel aches, pains or cramps in your lower back, abdomen, head or breasts, period pain can make life miserable.

Again, tracking it may help, as you should be able to spot patterns of when it might come and, importantly, when it might pass.

The NHS recommends over-the-counter painkillers, such as ibuprofen, for period-related pains.

However, if period pain stops you from living your life as you want to, it may help to consult your doctor.5

  1. Change in bowel movements

Changing hormones can make you retain more water during your period.

This can lead to feelings of bloating and gassiness and it can also affect your digestion; you might notice constipation or loose stools in the lead-up to your time of the month.

Increased progesterone levels in the lead-up to your period can also affect the gastrointestinal tract, causing either diarrhea or constipation.

  1. Increase in spots and pimples

Females are more prone to acne and pimples in general, and it is all because sebum (oil) production is affected by those pesky hormones.

Known as cyclical acne (because it comes and goes in cycles), the areas that are commonly affected are chin and jawline.

  1. Change in sleep pattern

Again, blame those hormones! They often make people feel much hotter before and during their periods, which can lead to restless and disturbed sleep.

But even if you do not feel like a furnace around your time of the month, the changing levels of progesterone and oestrogen (estrogen) might still change sleep patterns.

Either way, tiredness, and fatigue are common feelings around your period.

Irregular periods versus heavy periods

If you have irregular periods, they may or may not be classed as heavy periods, too.

Also known as menorrhagia, periods of bleeding that require a change of sanitary towel every hour or so might require further medical investigation.

Other indications that you might have heavy periods include passing large blood clots during your period (that are bigger than a 10p piece), and if one sanitary product alone is not enough and you regularly have to wear a tampon and a pad, for example.6

Heavy periods may require medication or further tests, such as an ultrasound, to rule out wider gynaecological problems.

Heavy periods can be symptom of issues such as fibroids, endometriosis, polycystic ovary syndrome, pelvic inflammatory disease.

When to see a doctor for irregular periods

If your periods have always been irregular, you may well be one of the people who simply have benign irregular menstruation patterns.

However, you should always see a doctor if you are worried.

This is especially true if you have noticed a sudden change, including late periods, or an early period.7

It is worth mentioning that it can be very helpful for doctors if you can monitor the changes with an app or a diary over a few months.

Handpicked content: What to eat during your menstrual cycle

The advice in this article is for information only and should not replace medical care. Please check with your GP or healthcare professional before trying any supplements, treatments or remedies. Food supplements must not be used as a substitute for a varied and balanced diet and a healthy lifestyle.

Last updated: 10 September 2021



Author: Bhupesh PanchalSenior Regulatory Affairs Associate

Joined Holland & Barrett: Apr 2019

Masters Degree in Toxicology and BSc Hons in Medical Biochemistry

Bhupesh started his career as a Clinical Toxicologist for Public Health England, advising healthcare professionals all around the country on how to manage clinical cases of adverse exposure to supplements, pharmaceuticals, cosmetics, industrial chemicals and agricultural products.

After 7 years in this role and a further year working as a drug safety officer in the pharmaceutical industry, Bhupesh joined Holland & Barrett as a Senior Regulatory Affairs Associate in 2019.

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