Irregular periods are not usually a sign of a problem. But speak to a GP if a person's periods are irregular or their normal pattern of periods changes.
Check if a person has irregular periods
The average gap between periods starting (the menstrual cycle) is 28 days. It can sometimes be a bit shorter or longer.
A person'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 periods to be irregular when they first start during puberty, and when a person is nearing menopause.
Keeping track of periods
Using an app or a diary to keep track of periods can help a person see if they're irregular.
Day 1 of the menstrual cycle is the first day of the period. The last day of the cycle is the day before the next period.
Causes of irregular periods
Common causes of irregular periods include:
- puberty, when a person starts their 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 polycystic ovary syndrome (PCOS) and an underactive thyroid gland can cause irregular periods.
Non-urgent advice: See a GP if:
- a person's periods are irregular
- their periods last longer than 7 days
- they have irregular periods and other symptoms like weight gain, tiredness, hair growth on the face, and dry or oily skin
- their periods are irregular and they're struggling to get pregnant
Treatments for irregular periods
Treatment is not always needed for irregular periods.
The GP may refer a person to a specialist (gynaecologist) if tests are needed to find out what's causing their 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 periods more regular.
Trying for a baby
Getting pregnant can be more difficult if a person has irregular periods because they might not release an egg (ovulate) regularly.
It can help to attempt conception every 2 or 3 days throughout the cycle.
If a person is struggling to get pregnant, hormone medicine or fertility treatment may be recommended.
