Irregular periods

Irregular periods are not always a sign of a problem. But sometimes it's a good idea to contact your GP about them just in case.

Symptoms of irregular periods

You have irregular periods if the length of your menstrual cycle (the gap between your periods starting) keeps changing.

Your periods may come early or late.

The average menstrual cycle lasts 28 days, but it's normal for it to be a bit shorter or longer than this.

After puberty, many women develop a regular cycle with a similar length of time between periods. But it can vary by a few days each time.

Causes of irregular periods

Common causes of irregular periods include:

  • puberty – your periods might be irregular for the first year or two
  • the start of the menopause (usually between the ages of 45 and 55)
  • early pregnancy – take a pregnancy test to rule this out
  • some types of hormonal contraception – such as the contraceptive pill or intrauterine system (IUS)
  • extreme weight loss or weight gain, excessive exercise or stress
  • medical conditions – such as polycystic ovary syndrome (PCOS) or a problem with your thyroid

When to contact your GP

You do not need to get medical advice if you have always had irregular periods or you're still going through puberty.

Non-urgent advice: Contact your GP if:

  • your periods suddenly become irregular and you're under 45
  • you have periods more often than every 21 days or less often than every 35 days
  • your periods last longer than 7 days
  • 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.

You might be referred to a specialist called a gynaecologist if you need any tests or treatment.

Trying for a baby

It can be more difficult to get pregnant if you have irregular periods because you might not ovulate (release an egg) regularly.

It can help to have sex every 2 or 3 days throughout your cycle. You do not need to time sex around ovulation.

Read more tips to increase your chances of getting pregnant.

You might need hormone medicine or fertility treatment if you're struggling to get pregnant naturally.


Content supplied by the NHS and adapted for Ireland by the HSE

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This project has received funding from the Government of Ireland’s Sláintecare Integration Fund 2019 under Grant Agreement Number 123.

Page last reviewed: 8 July 2021
Next review due: 8 July 2024