Most people who menstruate have their period around every 28 days, but it's different for everyone. Periods can range from day 24 to day 38 of your cycle.

Signs of irregular periods can include:

  • the number of days in between each of your periods is different and keeps changing
  • the amount of menstrual blood changes from one period to the next
  • your periods come closer together  less than 25 days from the start of one to the start of the next one
  • your periods come further apart  longer than 35 days between the start of one and the next one

Some people might have a less regular cycle, and experience a different cycle each month (this is often the case when girls first start their period). However, it can also be caused by things like stress, certain health conditions or pregnancy. Irregular periods can also be a sign of menopause. Most of the time there's no need to worry but sometimes it is important to speak to your doctor.

If you think you might be pregnant, it’s important to take a pregnancy test as soon as possible.

Further information on your options if you're pregnant

Non-urgent advice: Speak to your doctor if:

You're not pregnant and:

  • you have started your period but haven’t had one for a while (around 3 to 6 months)
  • you bleed between your period, after sex or after the menopause
  • you experience irregularities with your periods for example the number of days in between your period keeps changing
  • your periods are closer together or further apart than usual

If you’re seeing your doctor, there are some useful pieces of information to think about beforehand:

  • the first day of your last period (when it started)
  • how many days your period usually lasts
  • what was the shortest time between your periods (from the first day of one period to the first day of the next)
  • what was the longest time between your periods (from the first day of one period to the first day of the next)
  • how often you need to change your period products on a heavy day
  • if you are over 25, when you had your last smear test

It can be helpful to keep a note of your period dates and symptoms using a calendar, a diary or an app. You can then discuss this with your doctor who can decide if any tests or treatments might be needed.

Causes of irregular periods

Irregular periods can be caused by lots of different things, usually involving hormonal changes, including menopause or hormonal contraception.

Your menstrual cycle is regulated by 2 hormones, oestrogen and progesterone. Both of these hormones can be affected by natural changes in your body. For example puberty, pregnancy, childbirth, breastfeeding and menopause.

Your period will start during puberty. It can take up to 2 years for oestrogen and progesterone levels, and your periods, to settle.

Your period will stop during pregnancy but you might still experience some bleeding or spotting early on. If you’re worried about bleeding during pregnancy, speak to your midwife, doctor or local early pregnancy centre.

Most women won't have periods when they’re exclusively breastfeeding. But you can still get pregnant so you should think about your contraceptive options if you don't want another pregnancy.

Irregular periods can be common before menopause. The amount of menstrual blood can vary from one period to the next.

Other things that can cause irregular periods are:

  • stress
  • weight gain
  • eating disorders
  • extreme exercise
  • hormonal contraception

Irregular periods can also be caused by underlying health conditions, including:

  • endometriosis a long-term (chronic) condition where tissue similar to the lining of the womb is found elsewhere in the body
  • pelvic inflammatory disease – an infection of the womb, ovaries and/or fallopian tubes
  • fibroids – non-cancerous growths that can develop in the muscular wall of the womb
  • adenomyosis – when the tissue that normally grows within the womb (the lining) grows into the muscular wall of the womb instead
  • polycystic ovary syndrome – a hormonal condition which affects how your ovaries work
  • thyroid problems

In rare cases, irregular periods may be a sign of cancer of the womb or the neck of the womb (cervix). These cancers can cause bleeding in between periods or during sex. If you’re worried, speak to your doctor.

Last updated:
29 September 2022

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