What causes irregular periods?

Are irregular periods normal?


Having irregular periods isn’t always a cause for concern. While the average menstrual cycle lasts for 28 days, the length of a woman’s menstrual cycle can vary from 21- 40 days. It’s also perfectly normal for your cycle to vary slightly from one month to the next. 

Common factors which can influence irregular periods are: 

  • Puberty- in the first few years of getting your period they’re much more likely to be irregular 
  • Hormonal contraception- for example, the implant, IUS or mini pill
  • Excessive exercise 
  • Significant weight gain or sudden weight loss 
  • Menopause
  • Pregnancy 
  • Polycystic ovary syndrome (PCOS)

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Do I need to see a GP?

If you’ve always been irregular or you are on hormonal contraception then there’s no need to see a doctor. However, in some cases, this is advisable to make sure that there’s nothing underlying. For example:

  • If your periods have stopped and you’re not pregnant or using progesterone-only contraception 
  • If you bleed for more than 7 days during your period
  • If you’re getting your period before the 21 days window, or later than 35 days

In general, if you are worried then it’s best to discuss things with your GP who can either help to set your mind at ease or look into what might be causing problems with your period. 


Hormonal contraceptives 

Certain types of hormonal contraceptives can cause irregular periods. These include:

  • The hormonal IUS
  • The implant 
  • The mini pill
  • The injection 

Some women find that their periods stop altogether while using these methods, while others can experience an irregular cycle. This is perfectly normal. The combined contraceptive pill will usually have the opposite effect as it will regulate your period. 


Weight changes and dieting 

Losing too much weight too quickly can cause your periods to become irregular, or stop altogether. This can happen if you are not eating enough, as the menstrual cycle isn’t getting the nourishment needed to sustain itself or potential pregnancy. Crash dieting and excessive exercise are typically associated with this. 

This may also be a warning sign of an eating disorder, such as anorexia, which is a serious mental health condition. Being underweight and avoiding eating as much as possible are symptoms of this. It’s important to get help to prevent things from getting worse and causing serious complications. 


Polycystic ovary syndrome

PCOS is a fairly common condition. It’s caused by a hormonal imbalance, predominantly the overproduction of male hormones and causes issues in the ovaries. One major symptom of the condition is not having regular periods and struggling to get pregnant. You may also have problems with acne, oily hair or excessive hair growth. 


How can I regulate my cycle?

If you are finding irregular periods to be a nuisance, one option is to use the combined contraceptive pill. It contains progesterone and oestrogen hormones and works by preventing ovulation from happening. You’ll typically have a period after 21 days during the 7 day break between pill packs. At first, you might notice spotting or breakthrough bleeding but this will clear up after a month or so. 



NHS> Irregular periods:

NHS> Polycystic ovary syndrome (PCOS):

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