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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 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:

Sometimes, conditions like polycystic ovary syndrome (PCOS) and an underactive thyroid gland 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
  • 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.

Last Reviewed
16 April 2025
NHS websiteNHS website

Quality healthcare services

Established in 1983, Blackwells Chemist has been around for 43 years in the current hands of Piyush Amin, providing excellence care and personal professional advice. Over time, we have secured our reputation to thousands of patients as "their long term family pharmacist" due to our specialist advice, care and attention served and tailored to each and every patient and their needs.

As well as the standard pharmacy prescription services and healthcare retail products, we also offer a wide range of healthcare services including antigen and antibody testing, a travel and vaccination clinic, a seasonal flu & covid jab service, blood pressure monitoring, addiction clinics, health screening services, Pharmacy First and a range of over 12,000 product lines stocked in store.

We serve all of Beckenham, Bromley, Park Langley, Penge, Crystal Palace, West Wickham, Shirley, Eden Park, Elmers End, Shortlands and further afield. 

Ask your local GP about our sterling reputation, for both excellence in care as well as stocked products.
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Premises GPhC No:1032588
Superintendent Pharmacist: Piyush Amin (GPhC No. 2028679)
Owned by: Blackwells Chemist Limited
Company Reg: 07458651
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