causes of irregular periods

5 reasons for irregular periods

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:

  • 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.2

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.

2. Pregnancy

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

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

3. Some types of hormonal contraception

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

4. 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.

5. Some medical conditions

Common culprits include polycystic ovary syndrome and thyroid issues.

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.4

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.5

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.

Last updated: 23 October 2020