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Woman thinking about changes to her period

Changes to your period


Your periods can change in both length and in the amount you bleed, these changes can occur for a variety of reasons, some natural variation by a few days or teaspoons of blood can be expected.

Variety of reasons for period changes
period calender


If your period is late and you've had sex it may be worthwhile taking a pregnancy test. Some contraceptive methods have a higher failure rate than others.


Missed or late periods happen for many reasons other than pregnancy. Causes can range from hormonal imbalances to medical conditions. If you are concerned it could be worthwhile booking an appointment with your doctor.

period calender


Irregular periods are when the length of your menstrual cycle keeps changing, this isn't always a sign that something is wrong but it may be worthwhile booking an appointment to see you doctor just in case.


It normally takes the first couple of years when you start having periods for them to become regular.


A lot of exercise or stress and changes in weight can cause periods to become irregular.

Did you know?

Some types of hormonal contraception such as intrauterine systems (IUS) or the pill may disrupt your regular cycle.


If your periods…

...start to reduce in frequency over the course of months or years it could be a sign you are perimenopausal.


...have stopped unexpectedly you could be pregnant or experiencing the menopause.


...last longer than 7 days this could also be a sign of heavy menstrual bleeding.


If you are bleeding between periods, after sex or after the menopause it may be worthwhile booking an appointment with your doctor.

Woman concerned about changes to her period
Mum and daughter discussing heavy periods


It is not uncommon to experience heavier bleeding than usual on occasions but when does this become something you should speak to your doctor about? If your periods regularly last longer than 7 days and/or you regularly lose more than 13 teaspoons of blood this could be a sign of heavy menstrual bleeding (HMB), a legitimate medical condition.


Learn more

PP-UN-WHC-GB-0045 September 2023


The health information on this site has been reviewed and approved by Bayer by an appropriately qualified medical reviewer. It is intended as general information only. It is not intended to replace a consultation with a healthcare professional, to provide specific medical advice or replace the patient information leaflet provided with your medicine. Treatments discussed here should be initiated under medical supervision. For full information including side effects and eligibility for treatment, please consult your healthcare professional. Always speak to your doctor or nurse for personal medical advice.


Images on this site are stock images and for illustrative purposes only.


Reporting side effects

If you get any side effects whilst taking a medicine, talk to your doctor, pharmacist or nurse. This includes any possible side effects not listed in the package leaflet. You can also report side effects directly via the yellow card scheme at By reporting side effects, you can help provide more information on the safety of medicines.