Irregular Periods

What are irregular periods?

The average gap between periods starting (the menstrual cycle) is around 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:

puberty, when you start your periods
the start of menopause (usually between the ages of 45 and 55)
pregnancy - a missed period is often an early sign of pregnancy
hormonal contraception like the progestogen-only pill, contraceptive injection and intrauterine system (IUS)
losing or gaining a lot of weight
stress and anxiety
exercising too much

Sometimes, conditions like polyendocrine metabolic ovarian syndrome (PMOS) (which used to be called polycystic ovary syndrome PCOS) or thyroid problems, can cause irregular periods.

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
you have bleeding between periods
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 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 polyendocrine metabolic ovarian syndrome (PMOS) is causing irregular periods, the combined pill may help make your periods more regular.

If irregular periods are caused by other hormone problems, such as thyroid problems, medicines can help treat it.

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, you may be referred for further tests. Hormone medicine or fertility treatment may be recommended.

Find out more

Wellbeing of Women: periods information hub

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