The Causes of Irregular Periods

What can disrupt your menstrual cycle?

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Medically reviewed by: Dr Laura Joigneau Prieto

Last reviewed: 04 Mar 2019

Woman lying in a chair looking up the causes of irregular periods on her tablet

Key takeaways

  • There are many health reasons for irregular periods to consider

  • Your contraception could also cause your periods' timings to change

  • Pregnancy can also explain why your period isn't when it should be

  • You can control some of the causes of your period irregularity

  • It could be that you're having unexpected bleeding and not actually a period

Contents of this article

What can cause irregular periods?

There are many things that can cause irregular periods – the most common ones are:

  • Age-related – women who have just started their periods and women who are nearing the menopause commonly experience irregular periods.
  • Hormonal contraception – using the contraceptive pill, mini pill, progesterone injection, the hormonal coil, or implant, can cause changes in your period
  • The intrauterine device (IUD – a coil without hormones) – this may cause a heavy periods, mainly in the first months after it’s been placed
  • Fibroids – these are benign growths that are found in the womb. Fibroids can cause abnormal periods, pain or a feeling of pressure in the lower abdomen, or even difficulty in conceiving
  • Polyps – these are an overgrowth of glands within the womb. In most women, polyps are benign; however, in very rare cases it can be malignant
  • Adenomyosis – this happens when the inner lining of the womb breaks through into the deeper muscle layers
  • Changes in ovulation – a woman’s menstrual period is very closely linked with when her body releases an egg into the womb. Sometimes the body produces an egg less often than usual, or even not at all. This will cause changes in the menstrual cycle
  • Issues with blood clotting – there are many causes for this, including genetic conditions or certain medications
  • Other medical conditions – including polycystic ovary syndrome (PCOS) or problems with the thyroid
  • Pregnancy – in some cases there can be unexpected bleeding related to pregnancy

Sometimes irregular periods just happen – it’s important to remember that every woman is different. Having irregular periods doesn’t mean that there is anything wrong; it can be normal and expected in some women. However, if you have noticed a change in your own menstrual periods or if you are otherwise concerned, don’t hesitate to contact your GP to discuss this.

Why does contraception sometimes cause irregular periods?

Hormonal contraception can cause irregular periods – some methods of contraception use artificial versions of hormones that are naturally found in the human body. These hormones are used by the body to regulate your menstrual periods. Taking hormonal contraception affects the levels of these hormones in your body; so, taking contraception can change the menstrual cycle of some women. What happens to your periods depends on what type of contraception you’re taking and how your body reacts to them:

  • The pill, patch, or ring – when you use these types of contraception you have three weeks of taking hormones and a week ‘break’ where you don’t take any hormones. Most women experience bleeding during this one week break due to the decreased level of hormones called a ‘withdrawal bleed’. Spotting during the first few months of using these types of contraception is quite common. Some women prefer to take the pill back-to-back, without doing any break between two packs. There are different ways to do it: in some cases the pill is taken continuously for 3 cycles and then stopped for one week, other women take the pill continuously until some breakthrough bleeding appears, and make the break at that moment, and finally, some women take the pill continuously without any break despite having spotting. This way of taking the pill has its advantages, and the main inconvenient is that spotting or irregular bleeding might appear.
  • The mini pill – it’s difficult to predict how your body would react to the mini pill. Some women experience lighter and more irregular periods (some women even experience spotting throughout the month) whilst others experience heavier or more painful periods. Some women maintain their periods as previously, and some women don’t have periods at all.
  • The contraceptive implant – most women find that their periods are lighter on the implant. However, some find that their periods become heavier and others experience spotting after they’ve had their implant put in
  • The contraceptive coil – spotting is quite common in the first few months after the coil was put in. Most women wearing a hormonal coil find that their periods get lighter and more irregular, or don’t have periods at all. But others can experience heavier or more painful periods. Women wearing an intrauterine device (IUD) or coil without hormones usually experience heavier and more painful periods during the first few months, but this usually settles after 6 months and periods go back to how they used to be before the coil.

What to do about contraception and irregular periods – if you have just started a new method of contraception and are experiencing side effects, it may settle down within the first three months as your body gets used to the hormones. If you can’t tolerate these side effects or if you are otherwise concerned, don’t hesitate to speak to your GP. They’ll be able to assess the possible cause and propose the appropriate treatment. It’s sometimes necessary to change to a different method of contraception.

Can an irregular period mean pregnancy?

If you're not sure, take a test – lots of things can cause an irregular period and the only way to tell whether or not you are pregnant is to take a pregnancy test.

A period later than normal could mean pregnancy – if your period is late and you still haven’t had a period, you could be pregnant. Some people can have bleeding during pregnancy too, so if your period is lighter or different to normal, you should also take a pregnancy test. If you are on the Pill, patch, or ring, you will not experience a ‘withdrawal bleed’ if you are pregnant. This is because the pregnancy will override the hormonal changes that causes the withdrawal bleed.

What to do if you think you're pregnant – if you think you may be pregnant, it’s important to make an appointment with your GP as soon as possible. You can’t take emergency contraception as this only works for up to five days after you’ve had unprotected sex and won’t be effective if you’re already pregnant. Your GP will be able to advise you on the next steps to help you come towards a decision.

If you have irregular periods, you can't use the rhythm method as contraception – this is because the rhythm method relies on regular menstrual cycles to predict the fertile period (the period of a few days where you can become pregnant if you have unprotected sex).

What can you do about the causes of irregular periods?

Get your contraception checked – if you have irregular periods and this bothers you, you can speak to your GP about starting the Pill, patch, or ring. On these methods of contraception, women can decide when they have their periods. The most common pattern is to get a ‘withdrawal bleed’ 1 week in every 4 when they’re not taking any hormones, but women can also take the pill for 9 weeks before taking a 7-day break or even take it continuously without break. However, with this last schedule, you could have some light spotting at irregular times.

The mini-Pill, implant, and coils can also make periods lighter and less painful. However, the effect of taking these methods of contraception on a woman’s menstrual cycle is unpredictable.

Exercise and weight loss – if you experience heavy, painful periods, there are some things that you can do at home to help ease symptoms, such as doing gentle exercises like walking or stretching and using a water bottle to help ease any cramps. Irregular periods are also associated with women who have a BMI above or below the recommended range. So, keeping your BMI at a healthy range by exercising regularly and eating a balanced diet can help prevent you from having irregular periods.

Timing your periods when you need to – if you want to delay your period, we offer ten, twenty or 30 day courses of Utovlan. Utovlan is a medication containing hormones which delays your period. To get your supply you need to fill in a short questionnaire about your health which a doctor will review before sending the medication to you by post. Alternatively, you can speak to your GP or pharmacist about taking the Pill, patch, or ring without a week’s break in order to delay your period. You can take Utovlan if you’re using a progesterone-only pill, the implant, or the coil. If you’re currently using a combined pill, you don’t need to take Utovlan to delay your periods as you can do it by taking your packs back to back.

Is it an irregular period or unexpected vaginal bleeding?

Get checked by a doctor – sometimes a small injury to the vagina, cervix, or womb can be mistaken for an irregular period. To find out the cause of unexpected vaginal bleeding, you should make an appointment with your GP or a doctor in a sexual health clinic (sometimes called a genitourinary medicine or GUM clinic). The doctor will ask you some questions about your health and they may examine the vagina and cervix using a small instrument called a speculum. This can be a little uncomfortable, although it shouldn’t be painful. If needed, they might perform an ultrasound to check the womb, the endometrium (lining of the womb) and the ovaries.

In case of emergency – if you experience a sudden, severe abdominal pain with unexpected vaginal bleeding, you should call 999 or get someone to take you to your nearest A&E department. You may also feel dizzy, generally unwell, or you may even collapse. This could be a sign that you have a serious bleed and need immediate medical attention.

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Medically reviewed by:
Dr Laura Joigneau Prieto

Dr Laura Joigneau Prieto joined Zava in April 2018 as a clinical doctor. She studied medicine at the Universidad Autónoma in Madrid, Spain, and at the Pierre and Marie Curie Faculty in Paris, France. She did a Master’s Degree in clinical medicine in 2009 at the Rey Juan Carlos University in Madrid.

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Last reviewed: 04 Mar 2019

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