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Irregular periods

Irregular periods are not usually a sign of a problem. But speak to a GP if your periods are irregular or your normal pattern of periods changes.

Check if you have irregular periods

The average gap between periods starting (the menstrual cycle) is 28 days. It can sometimes be a bit shorter or longer.

A woman's periods are irregular if the gap between them is less than 21 days or more than 35 days.

Irregular periods can affect anyone who has periods.

It's more likely for your periods to be irregular when they first start during puberty, and when you're nearing menopause.

Keeping track of your periods

Using an app or a diary to keep track of your periods can help you see if they're irregular.

Day 1 of your menstrual cycle is the first day of your period. The last day of your cycle is the day before your next period.

Causes of irregular periods

Common causes of irregular periods include:

Sometimes, conditions like polycystic ovary syndrome (PCOS) and an underactive thyroid gland can cause irregular periods.

Non-urgent advice: See a GP if:

  • your periods are irregular
  • your periods last longer than 7 days
  • you have irregular periods and other symptoms like weight gain, tiredness, hair growth on your face and dry or oily skin
  • your periods are irregular and you're struggling to get pregnant

Treatments for irregular periods

Treatment is not always needed for irregular periods.

The GP may refer you to a specialist (gynaecologist) if you need tests to find out what's causing your irregular periods. If treatment is needed it will depend on the cause.

For example, if a condition like polycystic ovary syndrome is causing irregular periods, the combined pill may help make your periods more regular.

Trying for a baby

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

It can help to have sex every 2 or 3 days throughout your cycle without using contraception.

If you're struggling to get pregnant, hormone medicine or fertility treatment may be recommended.

Read more about trying to get pregnant.

Video: Menstrual cycle

This animation explains in detail how the menstrual cycle works.

Media last reviewed: 21 October 2023
Media review due: 21 October 2026

Page last reviewed: 26 July 2022
Next review due: 26 July 2025