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Irregular periods

5-minute read

Key facts

  • When you first start getting your period, it’s normal for your menstrual cycle to be irregular.
  • For most people, menstrual periods will eventually become regular, but some never develop a regular cycle.
  • There are many lifestyle factors and medical conditions that can cause your periods to become irregular. Treatment depends on the underlying cause.
  • See your doctor if your periods are irregular. Even if it doesn’t bother you, it’s important to check what is causing this and whether it is healthy for you.
  • If your period is late or has stopped, it’s very important to check if you might be pregnant.

How do I know if my cycle is normal?

Your menstrual cycle begins on the first day of your period and continues until (but not including) the first day of your next period. How long your period lasts and how often you get your period is different for everyone.

Normal menstrual cycles range from 21 to 35 days long, with an average of 28 days. Periods usually last from 3 to 7 days.

If you always have approximately the same number of days between periods, your menstrual cycle is regular. If your periods don’t follow a pattern, they are irregular. This is called oligomenorrhoea.

For a year or two after you first get your period, it’s normal for your menstrual cycle to be irregular. For most women, periods will eventually become regular. However some women never develop a regular cycle.

Should I be concerned if my cycle has changed?

Any change in your normal menstrual cycle may be a cause for concern. A change in your cycle could be:

  • you have a period more often or less often than is normal for you
  • your period does not come at all, this is called amenorrhoea
  • your bleeding is heavier or lighter than usual
  • your period is longer or shorter than is normal for you
  • you experience spotting (bleeding) between periods

CHECK YOUR SYMPTOMS — Use the Symptom Checker and find out if you need to seek medical help.

What causes periods to become irregular or stop?

If your period is late or has stopped, it’s very important to check if you are pregnant.

Periods can be irregular after childbirth, a miscarriage or if you terminate a pregnancy (have an abortion). Your periods might also become irregular in the years leading up to menopause, which is the stage when periods stop completely.

There are many other factors that may affect how often you get your period, such as:

How are irregular periods managed?

Because there are so many possible causes of irregular periods, any treatment will depend on the likely cause. Your doctor can arrange tests to find out what is affecting your periods.

Sometimes your doctor will recommend a lifestyle change, such as weight loss for women who are overweight, or exercising less if excessive exercise is the cause.

Your doctor might discuss a prescription for the oral contraceptive pill ('the pill') or the contraceptive vaginal ring to make your periods regular. These medicines contain two hormones, which take over your body’s natural hormones, oestrogen and progesterone, and control your menstrual cycles.

Even if you don’t mind having an irregular cycle, it may be unhealthy to go for long stretches of time without a period. Speak with your doctor to check if this is a problem for you.

When should I see my doctor?

It’s important to see your doctor if you experience any of the following:

  • your period comes infrequently (every 6 weeks or less often)
  • you have not had a period for 6 months or more
  • your period has come early or late for more than 3 months in a row
  • you experience bleeding between periods
  • you have not gotten your period by the time you are 16 to 17 years old

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Last reviewed: May 2022

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